DE2731646A1 - RIBBON DRIVE WITH CONSTANT TAPE SPEED AND TAPE TENSION FOR PRINTING SYSTEM - Google Patents

Description

2731648

"Ribbon drive with constant belt speed and tape tension for printing system "

The present invention relates to systems for conveying an elongated section of tissue between two rotatable reels and in particular on drive systems for a ribbon »attached between opposing spools in an impact printer.

Impact printers are known in which the individual hammers of a hammer bank strike an ink ribbon and press it against printing paper which is held by a roller during the printing process. The printing can be carried out in various ways, for example in the form of a dot matrix, the desired letters or other printed characters consisting of rows of dot-like spots produced by the hammers. The hammer bank can be related to the printing paper

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be moved back and forth to put the hammers in as much as possible cheaper way to use. The one on a pair opposite Rotatable spool-mounted reel-mounted ribbon can simultaneously move in the opposite direction between the spool-side Ends are moved to compensate for belt wear.

An example of a pressure system of this type is in U.S. Patent 3,941,051 issued March 2, 1976 to Barrus and others and assigned to the assignee of the present application. In that in the US patent application No. 495 830 described printing system, the opposite ribbon reels are driven by two AC motors driven, one of which acts as a pulling motor or a winding motor. The lagging or dispensing motor acts as a torque transmitter and exerts a constant torque. Because the diameter of the ribbon roll when it is transferred varies with the other roll, a constant speed of the take-up motor results in a proportional change in the Ribbon speed. The speed must be, for example, when doubling the diameter of the ribbon roll doubled in order to achieve a constant speed of rotation of the winding motor. The torque transmitter generates a tensile stress in the ribbon, which is in inverse proportion to the diameter of the ribbon on the torque sensor connected role. The tensile stress in the paint

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band also changes when the line voltage changes. A further change in tension results in places where a character is printed, since the torque sensor can either be at the pulling or at the pulled end of the ink ribbon, depending on the direction of movement of the ink ribbon, and there is also a sinking of the ink ribbon on the stationary guides for the ribbon can either increase or decrease the tension determined by the torque transducer. Since the pulling motor and the torque transducer are two separate units, it is not possible to reverse their roles if the direction of movement of the ribbon is reversed.

Further difficulties can arise if the hammer bank moves in both directions relative to the printing paper during printing. For the most powerful printing operations, there is a slow speed range in which printing with a new section of ribbon is possible in both directions. However, if no accurate speed control of the ink ribbon is carried out, a dense pressure, for example resulting in a "completely black print pattern", a horizontal cross-hatching when daa tape runs in a direction having a temperature below the necessary speed speed. Further difficulties arise from the fact that it is difficult to attach an error detection device, old in the direction of movement of the ribbon an interruption of the ribbon

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or the federal government itself can be proven. Prevent changes in the tension occurring in the belt the best possible guidance of the tape around the fixed guides that are used appropriately. Too strong Tensile stresses cause the edges of the tape to curl up or fold over one another on the guides. If the tension is too low, the result is that tape sections come to rest on other tape sections. when the tape runs slower relative to the printing paper Another disadvantage of an uneven tape speed in known tape drive systems results from that the printing on overlapping tape sections are not completely switched off when passing the print head can.

It is therefore desirable to have a tape drive system to create because the ribbon drives at a practically constant speed regardless of different ribbon arrangements on the rotating reels.

Ee also desirable to have a tape drive system to maintain a practically constant draw speed in the ribbon regardless of different ribbon arrangements on the spools.

It is also desirable to have a tape drive system to create no tachometers or similar devices for the detection of the belt speed or the tension needed in the tape, since a defective signal results if that

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Tape tears off or is not attached to the reels or if the drive stops, and that the functions of the Both motors when reversing the belt movement direction changes to a practically constant belt speed and Zigq tension in the band along with the other desirable parameters while the band in either of the two Directions is moved.

You are conveying ribbon drive systems according to the invention the belt with practically constant speed and constant tension independent of different, On the reels seated tape arrangements with the help of two coupled to the coils direct current motors with permanent magnets and with a circuit that the sum of the The currents flowing through both motors are kept practically constant, and the voltage at the one acting as a pulling motor is also kept constant Keeps the engine practically constant. It was found that the speed-torque characteristic of a direct current motor with permanent magnets provides the required motor characteristic approximates a given speed and a given ribbon tension very well. The pulling or winding one The motor conveys the tape at a practically constant speed regardless of what is wound on this reel Band part when the voltage drop is kept practically constant. The currents flowing through the two motors change in a complementary way. If the current flowing through the motor with the torrent coil changes like this,

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that the sum of the motor currents is kept practically constant, the tensile stress in the belt is practically constant held, regardless of changes in the banding technique on the reels.

The DC motors are via an arrangement with Power supplied, which has two servo circuits. These switch the motors between constant voltage power sources and a collecting line and are alternately operated according to the desired direction of movement of the tape drive taken. The servo circuit belonging to the take-up motor is made ineffective by placing the motor between the Constant voltage source and the collecting line is laid, so that the voltage occurring on the manifold den

Shows the voltage drop in the motor. The one assigned to the following motor or the motor for the supply reel Servo circuit, which is then effective, responds to the voltage appearing on the bus and delivers one Current through the motor for the supply coil, with which the voltage on the busbar is kept practically constant will. As a result, the sum of the motor currents is kept practically constant, resulting in a constant ribbon tension and Parbband speed results.

Various defects can easily be detected by monitoring the voltage on the bus line. A torn off, further unwound ribbon leads to the fact that the servo circuit of the leading motor the

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Motor voltage increased. There is thus an increase the voltage on the bus, and this is detected and used to signal this fault condition. A decrease in the voltage on the manifold is indicated by Circuits detected, which then signal a loose possession; this occurs when the winding bobbin is not properly attached to the axis of rotation. If the ribbon becomes jammed between the spools, it will result in a to strong current in the servo circuit of the winding motor, and this has the consequence that the output of the lagging servo circuit approaches the earth potential. Through this in turn, the current through the winding motor is increased and the voltage increases across a resistor located in the Manifold is arranged. This tension is detected and used to prevent the jamming of the ribbon to signal.

These and other objects, features and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment, which is illustrated in the accompanying drawings.

Figure 1 is a perspective view of a printing system incorporating the tape drive of the present invention.

FIG. 2 is a top plan view and block diagram of the tape drive system shown in FIG.

Figure 3 shows schematically the speed and the Current as a function of torque and explains the choice

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the reel drive motors and their operation in the ribbon drive according to the invention.

Figure 4 is a block diagram of the invention Ribbon drives.

Finally, FIG. 5 is a preferably detailed circuit which is used in the ribbon drive according to the invention.

For explanation, the inventive ribbon drive system is described with reference to a specific impact pressure system, which is shown schematically in Figure 1 and in detail in the aforementioned, co-pending U.S. Patent Application 495,830 is. However, it will be understood by those skilled in the art that the ribbon drive systems can also be used with other truck systems can and that they are also suitable when an elongated piece of fabric deviating from a color ribbon with constant Speed and should be moved with constant tension.

They shown in Figure 1, in the US patent application 495 830 is a printer for pages with 132 columns in data processing systems which typically 300 lines per minute on an original and a considerable number (e.g. 5) τοη Print out carbon paper copies. The main mechanical components of the printing device are shown in FIGS. 1 and 2 shown. The paper or other printable material

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consists of one or more webs of well-known, continuous or fan-shaped perforations on the side folded sheets, which are guided upwards by a base frame past a horizontal line printing position in which the printing process takes place. The original and the carbon paper copies are known along with Pulling devices 14, 16 moved past the position of the line printing, the pulling devices in the at the the perforations made on both edges of the paper. Below the print line is the paper 10 with an adjustable tension and is applied to a roller 18 without air pockets in between; the paper is held in place with the aid of a device 20 for adjusting the paper thickness.

At the level of the line in which the printing takes place, a shuttle mechanism 22 is attached, which is a Includes hammer mechanism that is moved back and forth in the horizontal direction and can sweep over a certain number of column positions. In the example it is assumed that 132 characters can be printed across the paper or that there are 132 columns. A group out 44 Hammering is used so that the lateral displacement of the pendulum mechanism 22 must be sufficiently large (7.5 mm in the example) so that each hammer can move across three adjacent columns. In Figure 2, the pendulum mechanism 22 is partially cut open to some

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To reveal hammers 24. Moved when pressed calibrate each of the hammers 24 under the action of a tension spring forward, with a pressure tip striking an ink ribbon 28 and this against the paper 10 long enough presses down to create a pressure pattern with the pressure tip, then the hammer returns to its original position. At the moment matrices are made of 5x7 and 9x7 points often used to create characters in dot printing systems. The hammers are turned back and forth simultaneously Moved to move in order to create points in a horizontal matrix of points in each of three related, to print out the column assigned to each hammer. The paper 10 is then fed into the position corresponding to the next horizontal line. The system uses it to print various character segments successively in the form of rows of points, first in one direction and then in the other direction.

In the printing position, the ink ribbon 28 lies between the shuttle mechanism 22 and the paper 10 and is over a supply roll 30 and a take-up roll 31 moved on. Vertical brackets 33 for the pendulum mechanism are attached to the base frame 12 and include longitudinal bearings 34 for receiving the horizontal support shafts 35, 35 '. The shafts 35, 35 'are fastened via brackets 36 to a horizontal part which has a housing 37 for the pendulum mechanism 22 forms.

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The hammer assembly mounted in the shuttle mechanism 22 is reciprocated by a cam assembly 38 which is described in detail in copending US patent application Ser. No. 495,330. A rotatable Cam follower rests on a double cam rotated by a shaft 45; Wave 45 is on not shown flywheel and a drive system coupled. A second rotatable cam follower is mounted on the opposite side of the cam in the axial direction in alignment with the first follow-up device and also rests on the cam. The second cam follower is housed in a counterweight structure that revolves around a shaft can rotate parallel axis. The second cam follower is pressed against the cams by a spring held·

In order to facilitate the continuation of the paper 10 beyond the print line, the pendulum mechanism is used rotatably mounted on the angles 36 between the shafts 35 »35 'which do not run in the axial direction. The pendulum mechanism is normally held in the pressure division with the aid of a tension spring 61 over which one of the Shaft downward angle 59 to frame 12 connected. A stop for the angle 59 is created by a friction bearing part 60 which is attached to the Surface of the flat parts attached to frame 12

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is present. The entire pendulum mechanism 22 can therefore

from half around the / shafts 35, 35 'defined axis from the at Print a line and move away from the position it is in thus gives a larger space between the hammer tips and the mechanism 20 for the paper; this makes the hammer mechanism accessible for cleaning purposes.

When the shuttle mechanism 22 moves back and forth in printing, the ribbon 28 becomes moved past paper 10 and roller 18; first, there is movement of the ribbon from spool 30 Coil 31 and then in the opposite direction from coil 31 to coil 30 instead. Whenever a ribbon end is wound on one of the reels 30 or 31, this condition is detected and the drive direction is vice versa. As a result, the tape is worn evenly over its entire length and fresh tape sections are available the hammers when striking the paper 10 available.

From Figure 2 it can be seen that the trailing reel or supply reel 30 is driven by a tracking or supply motor U2 . The leading or take-up reel 31 is driven by a feed or take-up motor H1. The motors M1 and M2 are fed via a control circuit 70. The ink ribbon 28 runs from the supply reel 30 via two stationary guides 72,

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The ink ribbon 28 goes from the stationary guide 74 between the pendulum mechanism 22 with its hammers 24 and the paper 10 held by the roller 16. At the opposite end, the ribbon 28 runs through two stationary guides 76 and 78, from which it is on the Take-up reel 31 is wound.

As already mentioned, the pendulum mechanism 22 is designed to be slidable against the paper 10 and the roller 18, so that each of the hammers 24 can carry out the printing process at different columns. At the same time, the ink ribbon 28 is transferred from the supply roll to the take-up roll 31 by the motors M2 and M1 controlled by the control circuit 70. The belt 28 is slightly inclined so that it appears to be offset diagonally to the shuttle mechanism 22, the paper 10 and the roller 18 with respect to the line to be printed. The band 28 is inclined from left to right below, so that the print line begins at the lower edge on the far left and ends at the upper edge of the tape on the far right. As a result, optimal utilization of the surface of the belt 28 is achieved. After the tape 28 has been completely wound onto the take-up reel 31, a detection device 80 responds to a wire attached to the tape or other devices provided on the end of the tape 28 and supplies a signal to the control circuit 70 for the motor, whereby the direction of rotation of the Motors M1 and M2 is reversed. The sink

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then becomes the take-up reel, while reel 31 becomes the supply reel, with the tape 28 then moving from the right to the left moved left. This movement of the tape from right to left continues until the tape has been completely wound onto reel 30. At this point one of the Coil 31 on a separate detection device 82 and supplies to the control circuit 70 a signal with which the direction of rotation of the motors M1 and M2 is reversed again. The tape 28 is then conveyed from left to right, with reel 30 serving as a supply roll, while reel 31 acts as a take-up roll.

It is true that the tape drive system shown in FIG suitable for two directions, but the reels 30, referred to as supply reel or take-up reel, since in known tape drive systems the motors M1 and M2 were not the same and functioned as a leading or winding motor or lagging or supply motor. In known systems, the motors are AC motors, the leading motor M1 runs at constant speed, while the lagging motor M2 acts as a torque transmitter exerts constant torque. The motor M1 normally overcomes the torque output by motor M2 and promotes the belt 28 from left to right. To the tape run in the opposite direction from right to left

that

Let’s let motor M1 be energized like that of motor M2

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torque generated exceeds the force exerted by motor M1.

Whenever one of the hammers 24 touches the ribbon 28 If the paper 10 presses on, printing ink is transferred to the paper 10 in the impact area. There remains dae The gang's service area without printer's ink until fresh printer's ink from the neighborhood enters it Area has flowed. For a given printer with hammers of known speed and size, the optimum ribbon speed can be determined at which the print image is evenly black with relatively dense printing, e.g. when printing a completely black point. In order to increase the service life of the belt and to ensure correct belt movement on the guides 72, 74, Also, to reach 76 and 78, the tape should travel at a constant speed.

The belt wear and the correct guidance of the belt also strongly depend on the tension in the belt. Tension on the belt is too high or too low with the result that the tape edges roll up or fold over each other when they are on the stationary guides 72, 74, 76 and 78 go by. Too much belt tension means excessive wear on the belt «· Too little Belt tension has the consequence that the belt is in the relatively small area between the pendulum mechanism 22 and the paper 10 jammed. It is therefore advisable to

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that the ribbon is continued with a certain, constant tension.

In known systems with alternating current motors for belt drive one tries constant belt speed and to generate constant tension in the tape over the reels 30 and 31 by the fact that the take-up motor M1 with constant speed and the lagging motor M2 operates with constant torque. However, since the size of the The tape sections wound onto the reels 30 and 31 cut each other changed, whereby the change in the diameter can be more than 2: 1, the belt speed and change the tension in the ribbon in a corresponding manner. In the tape drive systems according to the invention, the tape Moved on at a certain, constant speed and a certain, constant tension is created in the belt maintained, regardless of the changes in size of the tape sections wound on reels 30 and 31. This is achieved by using DC motors with permanent magnets as motors M1 and M2, as well as by using them a control circuit 70 which changes the current flowing through the trailing motor so that the voltage drop at the leading motor remains practically constant and that the sum of the currents flowing through the motors M1 and M2 is practically constant.

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In the example of a printing system shown in FIG. 1, the optimum ribbon speed is approximately 11.43 cm / sec and the optimum tensile stress occurring in the ribbon is approximately 394 g. The speed of one of the two motors M1 and M2 determines the speed of the associated reel 31 or 30. If one neglects the losses occurring due to friction in the motor and on the guides, the tape speed V _R for both reels can be as follows Expressed in the manner by the speed V ^ of the associated motor and the radius r of the section of tape on the reel:

(1) V _M = £ 60 (rpm).

ⁿ 2er

_{The torque T R} occurring at the two reels depends on the torque Tw of the associated motor and the radius r of the section of tape wound onto the reel and can be expressed as follows:

(2) T _M = T _R -r (g'cm).

From these two equations we get:

VpTp.60

If the optimum value of 11.43 for the belt speed cm / sec and the optimum value of 394 g for the tensile stress in the belt are used in the above equation, one obtains:

(I) V = 4.5 «Η · 60 602 / T l *> ^v m _2JtT - ^b ^ / ⁱ M

n.

The equation V _M = 602 / T _M expresses the relationship between engine

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BCpeed to the torque of the motor, if you have a Belt speed of 11.43 cm / sec and a tension of 394 g in the belt are used. This equation is derived from the hyperbolic curve 90 shown in FIG.

A first point 92 on curve 90 corresponds to one Tape roll radius of 2.54 cm, which in the present example means a completely unwound reel. A second point on curve 90 corresponds to the fully wound tape, the tape roll having a radius r of 4.83 cm. in the Ideally, one then obtains a constant belt speed of 11.43 cm / sec and a constant tensile stress of 394 g in the band through the use of a motor, its torque-speed characteristic is the same as the section of curve 90 located between points 92 and 94. An alternating electric motor is completely unsuitable because its torque-speed characteristic is a horizontal line in the representation chosen in FIG. The torque-speed curve a direct current motor with permanent magnets, which is fed with a constant voltage is a diagonal line that differs from a maximum speed on the y-axis in the unloaded state (Torque 0) extends to a maximum torque on the x-axis with the motor stopped (i.e. speed 0). Such a characteristic in the form of a straight line can represent an approximation of curve 90 between points 92 and 94.

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if you choose the parameters of the DC motor correctly. In the present case, a motor results in the Size class 12 shows the torque-speed characteristic curve shown in FIG. The maximum deviation of the characteristic curve 96 from the curve 90 occurs in the middle between points r = 2.54 cm and R = 4.83 cm and results in maximum fluctuations in belt speed and tension of 12 ^; this is significantly better than the fluctuations of 100% or more that occur in known systems. Curve 98 in FIG. 3 represents the characteristic of the motor current for the DC motor with permanent magnets used in the example.

In Figure 3, two different scales are used for the speed and two different scales for the torque. The speed scale labeled "Tip Gear Speed" and the torque scale ^{labeled "Tip Gear Torque '1} correspond to curve 90 and thus determine the speed and torque ranges that the motor must produce. The range of torque required at the tip gear would require an prohibitive size and high cost motor. A 12-size DC motor is therefore used with a gear arrangement that has a gear ratio of 34.1: 1. The desired torque occurs at the tip gear and is determined from the scale for the torque on the tip gear in

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Figure 3 shown. Similarly, the Top gear swept speed range of the Includes speed scale shown in Figure 3 for the tip gear. The speed and the torque that are output by the motor on the input side at the tip gear are determined by the "Motor speed" scales. and "engine torque" shown in FIG.

If DC motors with permanent magnets as motors M1 and M2 are used, the current I through the two motors can be expressed by the following equation (5) I =

where Κ «denotes the torque constant of the motor. Since the gear ratio is 34.1 and since the torque constant is 388 g.om/A, the Motor current with a fully wound tape with a diameter of 4.83 cm to:

(6) I = ?? ⁴ g 'hg? ^cm ,., - 0.143 A. ^v '34 \ f. 388 {g.cm/AJ '

The motor current for a completely unwound tape with r »2.54 cm is then:

- ° < ^{0755 A}

Since these values apply to the two motors and since the radii of the wound tape sections are complementary change, vary the flowing through the two motors

and

Currents also in a complementary manner / in the present example are 0.143 A + 0.0755 A or 0.2185 A.

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So that the tension in the belt remains constant, must the total torque of the motors M1 and H2 remain constant. The torque of each motor is proportional to the product from current and motor constant K ™. If it's two If similar motors are involved, the total torque is equal to the product of the motor constant K ™ and the sum of the two motor currents. If you therefore keep the sum of the motor currents constant, the total torque also remains and thus the tension in the belt is constant. By choosing a specific tension in the belt and by keeping the sum of the currents constant, a constant one is achieved Belt speed. Certain values of a constant belt speed and constant tension are therefore obtained by running the take-up motor with a constant Voltage and the supply motor with a current that keeps the sum of the currents of the two motors constant *. Since the two motors are of the same type, the roles of the take-up motor and the supply motor can be swapped for transport in both directions.

With the circuit shown in FIG. 4, the voltage at the winding motor and the sum of the currents flowing through the motors can be kept constant. The circuit shown in simplified form in FIG. A applies to the tape movement in a Rientnag, it being assumed that the motor M1 is the winding motor and the motor M2 is the supply motor. The output terminals 106 and 108 of the take-up

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motors M1 are connected to a constant _{voltage source V ß} and a common terminal 110 with the voltage V _g . _{The current I 1} flowing through the motor M1 flows from the common terminal 110 together with the current Ip * flowing through the motor M2 Earth-switched resistor Rp flows off. The terminals 112 and 114 of the motor M2 are connected to the output 116 of a differential amplifier 118 and the collective terminal 110, respectively. The non-inverting input 120 of the differential amplifier 118 is connected to a constant voltage source Vj, while the inverting input 122 is connected _{to the output 116 via a feedback resistor R p} and to the collective connection via an input resistor Rj _n.

The resistors R- and R ^ together with the differential amplifier 118 result in a servo circuit 124 which responds to the voltage V "at the common terminal 110 and produces a current Ip through motor M2, by means of which V_ is kept constant; In addition, the current I ₁ is influenced by the servo circuit in such a way that I- remains constant. The servo circuit 124 operates so that the voltage V _g appearing at point 110 becomes equal to the constant voltage Vjj. The differential amplifier 118 responds to the am

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reversing input 122 and seeks to make the voltage appearing at point 110 equal to voltage V ~ «. As will be described below with reference to FIG. 5, a servo circuit 124 is assigned to each of the motors M1 and M2. The two servo circuits are put into operation alternately during operation in both directions. As also described with reference to FIG. 5, the circuit shown in FIG. 4 is suitable for determining certain errors with a minimum of circuitry. If the tape jams on its way between the reels 30 and 31, the motor M2 produces a strong negative current, which results in a strong voltage drop across the resistor R ". This voltage drop across the resistor R _Q is used to signal the jamming of the tape. If one of the hubs to which the reels 30 and 31 are attached is loose, so that the tape does not advance, the voltage drop across the resistor Rq becomes very small. In this case, too, the voltage drop is detected and used to indicate a loose hub. During normal operation there is a considerable difference between the voltages applied to the two motors M1 and M2. However, if the tape breaks, both motors operate under similar conditions and the difference between the voltages applied to them becomes very small. This serves as evidence of a torn tape.

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FIG. 5 shows in detail a circuit for the motor control according to the invention with two alternately in operation taken servo circuits for operation in both directions; in addition, circuits for detecting voltage changes are shown in FIG. 5, whereby a Jamming of the tape, a loose hub or a torn tape can be detected as defect states.

The circuit shown in FIG. 5 comprises two servo circuits 124. The input resistor Rj _{n of} each servo circuit 124 is connected to the connection point 110 via a field effect transistor 130 or 132. The field effect transistors 130, 132 act as switches which are alternately opened and closed in order to alternately operate the two servo circuits 124. When the field effect transistor 130 becomes permeable and the field effect transistor 132 is blocked, the motor M2, which acts as a winding motor, is connected directly to a constant voltage source via a transistor 134. At the same time, the servo circuit 124 connected to motor M1 keeps the voltage drop across the transistor Rq and the total current I ™ constant. If the conductivity states of the transistors 130 and 132 are reversed, the blocking of the transistor 130 results in the motor M1 being connected directly to a constant voltage source via a transistor 136 so that this motor then operates as a leading motor. Simultaneously

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the transmissive transistor 132 makes the servo circuit 124 for the motor M2 effective, whereby the voltage drop across the motor M1 and the total current I. kept constant will.

The field effect transistors 130, 132 are operated via an input circuit which is applied to the laying of the tape <> uf the coils responds and two circuit sections 138, 140 with a flip-flop stage and several buffer stages 142, 144, 146 and 148. The circuit 138 is connected to the field effect transistor 132 via the buffer stage 142. The circuit is similar via the buffer stage 144 to the field effect transistor connected. The buffer stages 146, 148 are inserted between the field effect transistors 132 and 130 and a standby switch 150. Circuit 138 is on connected to a switch 152 which grounds a 5V voltage source through a wire running into the left end of the Ribbon is inserted; this occurs when the tape is completely unwound from the left side reel 30 has been. As a result, the flip-flop stage consisting of circuits 138 and 138 is switched over and leads to Grounding of the field effect transistor 132 via the buffer stage 142. As a result, transistor 132 is blocked and Motor M2 can work as a rewind motor. At the same time, the field effect transistor 130 is unlocked and leads for commissioning the servo circuit 124, which the

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Motor 141 is assigned. This servo circuit then leaves Motor M1 «» Is lagging motor working. When the tape has been fully wound on the left spool 30 so that the right spool 31 is empty, leads to a right side End of a piece of wire embedded in the tape to short the input of circuit 140 to the ground line and thus to switch the flip-flop stage. As a result, field effect transistor 130 is blocked and field effect transistor 132 unlocked so that motors M1 and M2 operate as leading and lagging motors, respectively.

When ready for operation, when the circuit shown in Figure 5 is supplied with power, but the tape is not moved further, the standby switch is closed, whereby the two transistors 130 and 132 be grounded via buffer stages 148 and 146, respectively. As a result, the two transistors 130, 132 are blocked, so that the motors M1 and M2 do not start.

The junction of the motor M2 with the transistor 134 is via a transistor 160 and a resistor 162 grounded; The connection point of the motor M1 to the transit gate 136 is via a traneistor 164 in a similar manner and a resistor 162 grounded. If motor M2 is switched so that it works as a take-up motor, the delivers Transistor 134 supplies current to motor M2 while transistor is biased so that it becomes virtually ineffective.

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transistor 164 is enabled and under certain circumstances then results in a significant negative current on the lagging motor M1, which results in a corresponding voltage drop across resistor 162. If motor M1 as engine running ahead is working, transistor 164 has practically no influence, but transistor 160 is biased, so that a relatively large current is delivered to the lagging motor M2; this has a corresponding Voltage drop across resistor 162. If the ribbon jams, the leading motor will remain stand and deliver a strong current to resistor Rq The lagging motor tries to push the belt further, which creates a strong negative current on one of the associated Transistors 160 or 164 and thus a large voltage drop across resistor 162 means. This voltage drop is via a comparator circuit 164 with the on one Voltage divider 166 compared voltage occurring; when the voltage drop is that given by voltage divider 166 Voltage exceeds, the output of the circuit arrives to a low potential, which signals the jamming of the band. In the previous operation, the voltage drop across resistor 162 is less than the voltage output by voltage divider 166, so that the output of the Comparator stage 164 is at high potential.

The voltage drop occurring across resistor R ₀ is combined with the voltage drop occurring across resistor 170

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Using a comparator stage 172 compared. If the The drive hub in one of the coils 30, 31 is not in contact with the coil so that the coil is not moved any further the lack of a torque on the motor a very low current flow through it and thus a reduction in the Voltage drop across resistor Rq. When the voltage drop If the voltage drop at resistor Rq falls below the voltage drop occurring at resistor 170, the output of comparator stage 172 comes to low values and signals a loose got. When this condition is corrected, the voltage drop across resistor Rq will be greater than that at resistor 170, and the output of the comparison stage 172 thus comes back to high values. When the system is first started, a switch 174 is temporarily closed, thereby grounding resistor 170; through this what is achieved is that the output of the comparison stage 172 reaches high values. When the switch 174 is released the step 172 remains in this state as long as no loose Vabe occurs.

A third comparator stage 180 is used for comparison a reference voltage with the voltage appearing at the junction of two resistors 180 and 182; the Resistors 180 and 182 are connected in parallel with motors M1 and M2. In normal operation, the The voltages of the motors so far that the voltage occurring at the junction of the resistors 180 and 182

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is smaller than the reference voltage, which has the consequence that the output of circuit 183 remains high. If the tape breaks or for other reasons If the tape runs away ("runs away"), the voltages of the motors and the potential of the connection point approach one another of resistances 1Θ0 and 182 increases to a value at that the output of comparison circuit 180 goes low; this indicates that the tape is running away.

It will be apparent to those skilled in the art that various advantages are achieved with the ribbon drive system of the present invention. Ink ribbon drives constructed and tested according to the invention have shown that the ink ribbon can be driven on the reels with an accuracy of ± 6% at a constant speed with changes in the pollen size of 2: 1; tachometers or other devices for measuring speed are unnecessary. The service life of the belt is increased if it runs at a constant speed, as this results in even wear over the entire length of the belt. This results in more uniform printing, mainly because the belt speed can be kept within the necessary limits and because the belt can be driven fast enough in the direction opposite to the shuttle mechanism to avoid overlapping adjacent spots on the belt surface. However, the tape movement is not too fast to keep up with the speed

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of the pendulum mechanism when the ribbon moves in the same sighting as the pendulum mechanism · The tension in the ribbon is kept constant with an accuracy of + 10 $, while the changes in the size of the ribbon rolls can be 2: 1; no monitoring devices are required for the tensile stress. The tape guidance is less critical, since the tension in the tape can be regulated within the limits required for good guidance. The system comprises two identical motors operated by two identical servo circuits, so that the functions of the motors can be interchanged when the direction of movement of the belt is reversed. As a result, the winding motor can always be used as a drive motor that determines the belt speed; the lagging motor or supply motor can act as a torque transmitter and thus determine the tensile stress in the belt. An interlock signal is generated indicating a torn or loose tape, an unattached spool, or a stalled motor. If necessary, the tension in the belt can be increased when the belt is at rest; this makes it virtually impossible for the ribbon to touch the paper and contaminate it. The belt speed and the tension of the belt do not depend on changes in the mains voltage because the servo drive is used. The · DC motor · have low inertia and respond quickly enough to reverse the direction of motion

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of the ribbon to restore the tension in the ribbon «

The present invention has been illustrated and described with reference to preferred embodiments, however, changes to details within the scope of the invention can be made immediately to the person skilled in the art.

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Claims (1)

Light · Or. Schmidt Hansmann · Herrmann P.O. Box 7O12O5 Munich 70 _{13 # JuU λ 977} Printronix, Inc. 1 7421 Derian Avenue Irvine, Calif. 92714 V.St.A. Claims .) System for conveying an elongated section of tissue, with two rotatable spools, an elongated, inserted between the coils, with opposite ends attached to opposite coils Section of tissue, two motors, each of which is coupled to one of the rotatable reels, characterized by Circuits for the excitation of the two motors (M1, M2) to thereby the elongated tissue section (10) between the Coils (30, 31) back and forth at a practically constant speed and practically constant tension conveying, regardless of variable decals made of elongated fabric material on the bobbins (30, 31) 2. System according to claim 1, characterized in that the circuits comprise means with which a - 1 -709885/0682 ORIGINAL INSPECTED practically constant tension on one of the two motors (M1, M2) is maintained, as well as others Devices with which the sum of the otröme flowing through the two motors (MI, M2) is kept practically constant will. 3. System according to claim 2, characterized in that each of the two motors (M1, M2) with a DC motor Permanent magnet is. 4. System according to claim 2, characterized in that the circuit comprises a collecting line (110) connected to the two motors (M1, M2), that a first constant voltage source is connected to one of the two motors (M1 or «M2) is connected that a second constant voltage source is used that a differential amplifier (118) is used, one output of which is connected to the other of the both motors (M1 or M2) is connected, and which has two inputs, one of which is connected to the second constant voltage source, and that a feedback circuit between the bus (110) and the other of the two inputs of the differential amplifier is used. 5. System according to claim 2, characterized in that the motors (M1, M2) are direct current motors that the Circuit common connection devices comprises that two constant voltage sources are provided that two Servo circuits (124) are used, each of which 709885/0682 contains one of the two DC motors (M1, M2) and is connected between the common connection devices and one of the two constant voltage sources, that each of the servo circuits generates a current through the DC motor contained in it during operation, the keeps the voltage at the common connecting devices practically constant, and that devices for alternating start-up of the two servo circuits (124) are provided. 6. System according to claim 5 »characterized in that each of the DC motors (M1, M2) has two connections, that each servo circuit (124) contains a differential amplifier (118), one output of which is connected to one of the two Terminals of the respective DC motor is connected, and has two outputs, one of which is connected to one of the two constant voltage sources is connected that facilities are provided with which the other of the both terminals of the respective DC motor is connected to the common connecting devices that a first resistor between the common connection devices and the other of the two inputs of the Differential amplifier is connected, and that a second resistor between the output and the other of the two inputs of the differential amplifier is switched. 7. System according to claim 5 »characterized in that 709885/0612 2731645 the circuits contain devices responsive to an increase in voltage at the common junction respond to signal a runaway of the elongated tissue section. 8. System according to claim 6, characterized in that the circuit comprises a voltage divider network which is inserted between the other of the two terminals of each of the DC motors and devices which are connected to a address certain voltage changes in the voltage divider network in order to signal that the elongated tissue section is running away. 9. System according to claim 5, characterized in that the circuits comprise means which are based on a Voltage drop on the common connecting devices respond to the state of a loose item on the elongated To signal tissue section. 10. System according to claim 5 »characterized in that the circuit comprises devices which respond to a decrease in the voltage in one of the two servo circuits (124) respond on the side of the associated DC motor opposite the common connection devices to a To signal jamming of the elongated tissue section. 11. System according to claim 6, characterized in that the circuit contains two Tran * istoren, each of which to one of the two terminals of one of the two DC motors is connected that a reference terminal is provided that 709885/0612 a resistor is inserted between the reference terminal and each of the two transistors, and that means are provided, which respond to a specific voltage drop across the resistor to prevent jamming of the elongated To signal tissue section. 12. System according to claim 1, characterized in that the elongated fabric section consists of an ink ribbon (28), that a roller (13) is provided, that devices are provided with which a printable material (10) against the surface of the roller (18) is pressed so that the printable material is located between the roller and a section of the ribbon (28) that next to the ribbon section a hammer bank is attached to the printable material (10) and the roller (13) remote side of the ribbon (28) is attached and in relation can move back and forth on the printable material and the roller, and that the hammer bank has several hammers (24) includes, with which the ribbon and the printable material are hit against the roller. 13 · System according to claim 1, characterized in that a first and a second direct current motor (M1, M2) each with first and second terminals used that the circuit has a common, to the first terminal the connection point connected to the first and the second DC motor comprise a common reference voltage source, a common connection point between the common connection point 709885/0602 ~ ⁶ ~ 2731648 and the common reference voltage source an inserted resistor, first and second constant voltage sources, and first and second differential amplifiers each having one output terminal and two differential input terminals are provided that one of the input terminals of the first differential amplifier to the first constant voltage source is connected that one of the input terminals of the second differential amplifier is connected to the second constant voltage source that the output terminals of the first and second differential amplifiers to the second terminal of the first and second DC motors, respectively are connected that first and second feedback resistors between the output terminal and the other of the two differential input terminals of the first and the second differential amplifier are used that first and second input resistors at the other of the two differential input terminals of the first and the second differential amplifier are connected, and that first and second switches between the common Connection point and the first or second input resistor are connected. 14. System according to claim 13, characterized in that the first and the second switch consist of a field effect transistor with a control electrode, and that alternately the control connection of one of the field effect transistors forming the first and the second switch 709888/0692 " ⁷ " 2731648 The occurrence of external control signals. 15. System according to claim 14, characterized in that Devices for earthing the two control connections of the als first and second switch-acting field effect transistors used when an external ready signal occurs will. 16. System according to claim 13, characterized in that two between the second terminals of the first and the second DC motor in series resistors are provided, and that means between the pair the resistors are inserted and respond to a certain increase in voltage between the resistor pair, to generate a signal that characterizes the uncontrolled running of the ribbon. 17 · The system of claim 13, characterized by a pair of first transistors, each of said second direct current motor and the output of the first and second differential amplifier is inserted β between the second terminal of the first and, an output connected to the common reference voltage resistance, a pair of second transistors, each interposed between a different one of the first two transistors and the resistor, and by means connected to the resistors, responsive to an increase in the voltage drop across the resistor by a predetermined amount and generating a signal indicative of blocking. 709886/0612 2731648 18. System according to claim 13, characterized by devices which are connected to the common connection point and which respond to a decrease in the voltage at this point and which generate a signal indicative of a loose signal. 709885/0692