EP0093389B1 - Oscillating mechanism for rectilinear and uniform shuttling motions of a carrier or the like - Google Patents

Description

The invention relates to an oscillation mechanism for rectilinear, uniform back and forth movements of a carrier or the like. By means of a linear drive, in particular a carrier for a matrix printing device, which can be moved in the line direction in front of a record carrier that can be advanced perpendicular to the line direction, the carrier being clamped in a frame , parallel bending elements is supported, the linear drive consists of an electrically driven linear motor, which is arranged in a housing, the linear motor has magnetic means and a movable electromagnetic coil, the polarity of which can be changed and the electromagnetic coil to power supply means and control means for the polarity and magnitude of the current flow electrically connected. Such a solution is known from US-A-3911814.

Various types of character or line printers using the dot-matrix printing method have been proposed which are put to practical use. Generally speaking, matrix line printers comprise a printhead or a hammer bank with a multiplicity of dot printing elements, each printing element forming a dot on the recording medium when it strikes. These dot printing elements lie in a row, which in turn is perpendicular to the direction of the conveyance of the recording medium. Since: the conveying direction of the recording medium is normally vertical, the dot printing elements are usually in a horizontal row. On the side of the paper facing away from the dot printing elements there is a support, i.e. a roller, and an ink ribbon between the dot printing elements and the recording medium. During printing, the dot printing elements are actuated, so that one or more dots appear on the recording medium in the printing series described by the dot printing elements. The recording medium, usually paper, is moved step by step after printing a dot series. Continuous movement of the record carrier is also possible. A series of rows of dots in the direction of the movement of the recording medium horizontally forms a series of characters, such characters being able to consist of alphanumeric characters.

Although the present invention was developed to move the printhead or the hammer bank of a matrix line printer back and forth and is therefore primarily used in printers of this type, the invention can also be used to support other devices that are accurate Moving back and forth at a controlled speed requires moving back and forth.

In general, in contrast to serial printers, matrix line printers can be divided into two categories. The first category of matrix line printers is based on the system in which only the dot printing elements are moved back and forth. The second category of matrix line printer contains dot printing elements with which the entire printhead, i.e. the actuators for the point pressure elements are moved back and forth. The individual parts of the dot printing elements, which have to be moved back and forth, are mounted on a carrier, carriage, carriage or the like. It does not matter what type of matrix printers it is. The present invention is suitable for both categories of matrix line printers.

Various types of swing mechanisms for matrix line printers have been proposed. A known type contains a stepper motor which is set relative to the carrier in such a way that individual steps of the carrier can be carried out. At the end of each step, the corresponding actuation devices for the dot printing elements are excited so that dots are imaged on the recording medium. Printing in both directions of movement is made possible by first moving the carrier or the carriage gradually in one direction and then gradually moving it back in the opposite direction. A major disadvantage when using. Stepper motors in matrix line printers, in particular in those matrix line printers in which both the actuating devices and the associated dot printing elements go back and forth. is the fact that conventional size stepper motors do not have enough power to move the print head of these matrix line printers. Such stepper motors of conventional size only have sufficient power to move the dot printing elements back and forth on their own, so that they are only advantageous in borderline cases for matrix printers in which the entire printhead or hammer bank moves back and forth becomes. In addition, stepper motors are limited in their speed, so that they are suitable for matrix line printers with a relatively high speed, i.e. with a printing capacity of 600 and more lines per minute are not suitable.

Because of the above-mentioned disadvantages of stepper motors, attempts have been made to use AC motors with constant speed and DC motors for the oscillating movement of the print head or the hammer bank of matrix line printers. A major disadvantage of the oscillation mechanisms, which operate on the basis of motors with constant speed, lies in the coupling devices by means of which the motors are coupled to the print head or to the hammer bank. In most cases, a cam curve with a force-fitting plunger device serves as the coupling device. However, both the cam curve and the ram device are subject to high mechanical wear and are therefore unsuitable for the very precise pendulum mechanism of a matrix line printer. More specifically, Ma trix line printers, which are operated at high speed, must be precisely positioned with respect to the print head or hammer bank when the dot printing elements are actuated. Mechanical wear is therefore extremely disadvantageous because it affects the accuracy of the positioning of the print head. However, if the accuracy of the printhead positioning deteriorates, defects in the print image arise. The result is distorted and / or blurred lettering and representations. However, such distortions and blurrings are not acceptable where high quality printing is required or desired. In other words, high quality printing requires a matrix line printer where the dots in each row of dots are in exactly the same location as the printhead or hammer bank is reciprocated.

Another disadvantage of known oscillation mechanisms that work with constant-speed motors and whose coupling devices consist of a cam curve with a cam follower can be seen in the fact that the movement-time curve is not linear. However, this fact means that relatively complicated position sensors and control systems are required in order to achieve precise point positioning with such oscillation mechanisms.

In order to switch off the mechanical wear and the non-linear movement-time curve of previous systems when mechanically coupling a motor at a constant speed to the print head or to the hammer bank of a matrix line printer, a coupling system with a was already proposed (European patent application 0044415) Use a pair of elliptical discs or gears. The coupling device described by means of elliptical, second-order wheels provided with two hoops are connected to one another either directly or with a 90 ° phase offset. Although such a coupling device produces a very precise movement-time curve, it is associated with undesirable noises and the coupling device is also mechanically complicated and more expensive to manufacture than would be desirable.

In addition to the stepper motors and constant speed motors, it has also already been proposed (US Pat. No. 3,911,814) to use linear motors for the back and forth movement of the carriage of printers.

Such a linear motor is a motor in which the axis of movement of the movable motor element is straight and not rotating. From the cited document, an oscillating mechanism for straight, uniform reciprocating movements of a hammer bench support between two positions is known. In one position the hammers are aligned with odd drawing positions and in the other position with even drawing positions. In response to control signals, the hammer bank is actuated to print a character as soon as the corresponding dot printing element is aligned with the assigned hammer. In other words, the device is intended for use in a type printer and not in a matrix printer. It is understood that a type printer does not require the same precise printhead positioning as a matrix line printer.

Another proposal for the use of a linear motor in a matrix line printer is known from US Pat. No. 4,180,766. In this system, the reciprocating drive mechanism that supports the hammer bank is subjected to free flight with little friction on a particular axis parallel to the line direction. At the end of each movement, the drive hits a sprung stop that reverses the direction of movement of the drive and thus the hammer bank. Energy losses that occur during the reversal are absorbed with the help of an energy pulse, a coupled linear electromagnetic drive and a connected speed compensation system, so that there is no need for precise servo control during the reversal and the drive reversal is caused by the rebound. During the reversal, the speed compensation system, which is fully utilized, senses the zero movement of the drive and reverses the direction in which the electromagnetic drive is energized. At the same time, the hammer bank speed is sensed during the movement by means of a pressure passport, and additional kinetic energy is applied by the speed assist system in order to compensate for the friction losses and the braking effects during printing and other changes in the hammer bank speed.

The reciprocating linear actuator described in U.S. Patent 4,180,766 has a number of disadvantages. For example, the use of a low-output motor, which essentially serves to cover the friction and pressure load losses, leads to a system with a long return and return time, so that the printer works slowly overall. This non-desirable property is further burdened by the rebound system in contrast to an energy storage system that would improve the oscillation time. The type of device described also requires several oscillating movements before the forward or reverse speed has reached the desired printing speed. The known printer therefore has a disadvantageously long start-up time, which is undesirable.

The invention has for its object to provide an oscillation mechanism for a rapid oscillation movement, which is simple in construction, requires little drive energy and whose drive energy can be regulated precisely.

The stated object is achieved according to the invention in the initially described oscillation mechanism in that the housing is supported on separate, likewise clamped, parallel bending elements that the resonance Vibration frequency of the combination of the linear motor and the housing bending elements is matched to the resonance vibration frequency of the combination of the carrier and the bending elements of the carrier, and that a connecting element coupled to the electromagnetic coil is provided between the electromagnetic coil and the carrier.

Such an oscillation mechanism is suitable for rapid movements of the print head or hammer bank, is clearly structured and the movement steps can be precisely positioned, i.e. can be set. In addition, the structure is simple and the physical requirements for movements over a short distance are created. It is also advantageous that when the printhead or hammer bank moves in one direction or the other, the bending elements store energy which can be used to reduce the time for reversing the movement at the end of the stroke. Another advantage is based on the fact that the resonance oscillation frequency of the combinations mentioned can be easily matched to the number of strokes of the movements of the carrier. The oscillating mechanism is also easy to control and the power supply to the electromagnetic coil is also easy to implement. The linear motor mounted by means of bending elements is advantageously arranged such that the axis of movement (preferably coaxial) is aligned with the axis of movement of the printhead or hammer bank. In this case, the electromagnetic coil is advantageously coupled directly to the printhead or to the hammer bank, an interaction of the forces of the bending elements with the forces generated by the electromagnetic coil being of particular importance.

The oscillation mechanism can now be designed particularly quickly in that the spring constant of the bending elements supporting the carrier is selected such that the resonance oscillation frequency of the combination of the carrier and the bending elements largely corresponds to the reciprocating frequency.

A clear and therefore well-functioning structure of the electrical circuit also results from the fact that the control means for the polarity and magnitude of the current flow in the electromagnetic coil from a position sensor for the position of the carrier from means for the continuous generation of an actual position signal, from means for the continuous generation of a target position signal, from means for comparing the actual position signals with the target position signals, from means for generating deviation signals from the size of the difference between actual and Sofl values and from means for regulating the current flow in the electromagnetic coil according to polarity and size.

To increase the speed of the system, it is also proposed that the means for the continuous generation of a target position signal have a main controller for generating the target position signals in digital form and a digital-to-analog converter, and that the actual position signals, which are present in analog form, together with the analog target position signals in analog signal means are compared.

A precise control of the electromagnetic coil is further supported in that the means for regulating the current flow in the electromagnetic coil include a pulse width modulator.

This precise control of the electromagnetic coil is also served by the suggestion that the means for regulating the current flow in the electromagnetic coil have a bridge circuit that contains four switches, one switch in each case in a bridge branch and the electromagnetic coil in the bridge diagonal and one bridge branch to it Power source is connected, and that the pulse width modulator generates four output control signals at the four switches.

The determination of the actual values or the generation of actual position signals is supported in that the position sensor for the position of the carrier has a light source, a pair of photocells assigned to the light source and a slide which has a pair of windows and which is connected to the carrier .

It is advantageous that the photocells consist of elongated, approximately equally sized photoelectric cells.

The determination of the actual values is further favored by the fact that the windows in the photocells are roughly the same size, elongated in shape and offset in the longitudinal direction.

The fast and precise determination of the actual values also serves to ensure that the windows extend in the direction of the elongated photo cells.

The transmission of the actual values determined by the position sensor is also improved in that the position sensor has a differential comparator which is connected to the photoelectric cells, the output signal forming the actual position signal in accordance with the voltage difference.

The actual value determination also advantageously serves that the position sensor is connected to a light control circuit which is connected to the outputs of the photoelectric cells and to the light source.

• Fig. 1 den zusammengebauten Schwingmechanismus und hierbei die Lage des Druckkopfes sowie die übrigen Bauteile für einen Matrix-Zeilendrucker,
• Fig. 2 einen senkrechten Querschnitt des in Fig. 1 dargestellten Linearmotors,
• Fig. 3 ein Blockdiagramm zur Ermittlung der Ist-und Soll-Werte sowie zur Steuerung der Druckhämmer in Abhängigkeit der Bewegung des Druckkopfes,
• Fig. 4 einen elektrischen Schaltplan mit den elektronischen Bauteilen für die Ermittlung der Regelungsgrössen, deren Verarbeitung und deren Verwendung als Steuerbefehle für die Druckhämmer.

An embodiment of the invention is shown in the drawing and will be described in more detail below. Show it

• 1 shows the assembled oscillating mechanism and here the position of the print head and the other components for a matrix line printer,
• 2 is a vertical cross section of the linear motor shown in FIG. 1,
• 3 shows a block diagram for determining the actual and target values and for controlling the print hammers as a function of the movement of the print head,
• Fig. 4 is an electrical circuit diagram with the electronic components for determining the control variables, their processing and their use as control commands for the print hammers.

Fig. 1 shows the print head 11 or the aforementioned hammer bank of a matrix line printer, which is supported by a pair of bending elements 13 and 15. The print head 11 and the hammer bank are not part of the invention and are therefore not shown in detail. The bending elements 13 and 15 are preferably formed from elongated, flat spring steel pieces which are attached on one side to the frame 16 of the matrix printer. The bending elements 13 and 15 are also aligned in parallel and, due to the length of the print head 11, are spaced apart.

The print head 11 is mounted between the movable ends of the bending elements 13 and 15, so that it moves at right angles in the direction of the arrow 17. The arrow 17 runs parallel to the longitudinal axis of the print head 11 and at right angles to the parallel planes of the bending elements 13 and 15.

The length of the print head 11 corresponds essentially to the width of the largest recording medium 21 which can be recorded by a matrix printer. The printhead 11 can have, for example, 66 separate dot printing elements, each of which is designed to scan or cover two character positions. The total or maximum character line width of such a printer is therefore 132 dot characters. Since the number of character positions (2) to be scanned is small compared to the number of dot printing elements (66), the movement path is small compared to the length of the print head.

For a better understanding, FIG. 1 shows the print roller 19 parallel to the print head 11 on the other side of the recording medium 21 as seen from the print head. 1 does not show how a suitable ink supply (such as an ink ribbon) works, which must be arranged between the print head 11 and the recording medium 21. The bending elements 13 and 15 lie next to the edge of the recording medium 21.

The linear motor 23 is located on one side of the print head 11, specifically directly next to the bending element 15. The housing 25 of the linear motor 23 is supported by a pair of bending elements 27 and 29. One side of the bending elements 27 and 29 are attached to the frame 16 of the matrix printer. The other sides of the bending elements 27 and 29 support the housing 25 of the linear motor 23. The bending elements 27 and 29 are preferably formed from flat spring steel pieces that run parallel to one another, but also parallel to the planes of the bending elements 13 and 15.

The linear motor 23 is arranged such that the axis of movement of the electromagnetic coil 31 of the linear motor 23 is coaxial with the longitudinal axis of the print head 11. The electromagnetic coil 31 of the linear motor 23 is coupled to the adjacent side of the print head 11 via a connecting member 33. Thus, when the electromagnetic coil 31 of the linear motor 23 oscillates back and forth, as will be described in more detail below, the print head 11 is moved back and forth in the direction of the arrow 17. As is easy to understand, such matrix line printers can be used as character and plotter printers. A matrix line printer designed in accordance with the invention is suitable for both operating modes. When used as a character printer, the movement of the electromagnetic coil is somewhat larger than the width of the number of character positions to be scanned by the print head 11, as specified in the example with two.

2 schematically shows that the electromagnetic coil 31 of the linear motor 23 is arranged such that it can be moved back and forth in the housing 25 of the motor. The housing 25 contains a permanent magnet 35, which preferably has a cylindrical shape. One side of the cylindrical permanent magnet 35 is closed by a plate 37, the magnetic resistance of which is low (e.g. ferromagnetic) and which forms a stud 39 in the middle. The size of the electromagnetic coil 31 is such that it surrounds the stud 39 with play. The other side of the cylindrical permanent magnet 35 is covered by the plate 41 (also included with low magnetic resistance), which has a central opening 43 through which the electromagnetic coil 31 extends. The magnetic flux generated by the cylindrical permanent magnet 35 has the flow directions indicated by the arrows in FIG. 2. This magnetic flux interacts with the magnetic flux which is generated by the electromagnetic coil 31 when, as a result of the application of current to the electromagnetic coil 31, electrical current flows therein. Depending on the direction of the current flow, the electromagnetic effect is such that the electromagnetic coil 31 is either pulled into the housing 25 or pushed out of it. The current direction of current thus controls the current direction of movement of the electromagnetic coil 31 and thus the current direction of movement of the print head 11. The magnitude of the current flow regulates the magnitude of the coil attraction or recoil force.

The spring constants of the bending elements 27 and 29 are selected so that the oscillation mechanism acts in a manner that compensates for vibrations. This means that the resonance vibration frequency of the linear motor 23 and its bending elements 27 and 29 is matched to the resonance vibration frequency of the carrier 11 and its bending elements 13 and 15. In addition, the resonance frequency is at or near the reciprocating speed. The energy requirement for the oscillation mechanism is therefore low.

3 illustrates a block diagram illustrating the preferred embodiment of a linear motor oscillating mechanism in accordance with the invention in conjunction with printhead 11 of a matrix line printer. In addition to the print head 11, the linear motor 23 and the connecting member 33, which are also shown in FIG. 1 and described there, FIG. 3 also contains a position sensor 51, a main controller 53, a tilt controller 55, a tilt comparator 57 and a switching amplifier 59 , a print hammer release controller 61, a print hammer release comparator 63, and a print hammer release circuit 65.

As indicated by the broken line, the position sensor 51 is connected to the print head 11 so as to continuously scan the position of the print head 11. Based on the information received, the position sensor 51 generates an actual position signal, which is applied to an input of the tilt comparator 57 and to an input of the print hammer trigger comparator 63. The main controller 53 generates control signals which are applied to the second input of the tilt comparator 57, specifically via the tilt controller 55 and via the print hammer release controller 61 to the second input of the print hammer release comparator 63. The output of the tilt comparator 57 is connected to the control input of the switching amplifier 59. The switching amplifier 59 is connected to the electromagnetic coil 31 of the linear motor 23 and controls the size. and direction of current flow. Thus, the output signal generated by the tilt comparator 57 controls the operation of the linear motor 23.

The output of the print hammer release comparator 63 is connected to the print hammer release circuit 65 for the purpose of controlling the point in time for the triggering process of the actuating devices for the individual dot printing elements in the print head 11 and thus the point in time of the printing process on the recording medium 21:

In operation, the main controller 53 generates control signals suitable for controlling the printhead position and the printhead position in which the actuators for printing the dots are released. More specifically, the main controller 53 generates printhead position control signals, i.e. Target position signals in digital form. The tilt controller 55 converts the digital signals into analog signals and applies the analog signals to the tilt comparator 57. The tilt comparator 57 compares the analog signal generated by the tilt controller 55 (the desired position signal) with the actual position signal generated by the position sensor 51. As a result, the tilt comparator 57 generates a deviation signal, which is fed to the switching amplifier 59. The switching amplifier 59 then applies a current to the electromagnetic coil 31 of the linear motor 23, the size and polarity of which moves the electromagnetic coil 31 in a direction which brings the print head 11 into the desired position. This means that the switching amplifier 59 connects the electromagnetic coil 31 of the linear motor 23 with a correction current. In the same way, the print hammer trigger controller 61 receives digital signals from the main controller 53 with the position of the print head 11 in which the print hammers are to be set. An analog signal is generated accordingly. This analog signal passes through a feed circuit, before it is compared with the actual position signal in the print hammer release comparator 63. When the printhead 11- reaches the position where the print actuators are to be energized, the print hammer trigger comparator 63 generates a trigger pulse. The trigger pulse enables the print hammer trigger circuit 65 to transmit actuation signals to the corresponding actuators. More specifically, in addition to the trigger pulse, the print hammer trip circuit 65 receives signals indicating which of the (e.g. 66) actuators should be energized when the position is reached, determined by the position of the control signals generated by the main controller 53, and implemented by the print hammer trip controller 61. The trigger pulse occurs through the pre-circuit before the point pressure position is reached. The lead time is chosen so that it corresponds to the time that the dot printing elements need to get from their rest position to the dot printing position on the recording medium 21. Which of the actuating devices should be energized first of course depends on the type of characters or the image to be created. The selection of the devices to be operated is made by the main controller 53 or another data source, e.g. a character generator. Regardless of the trigger information source, the corresponding actuators are only energized when the print hammer trigger comparator 63 generates a trigger pulse. In summary, the print hammer trigger comparator 63 generates a signal that merely indicates that the print head 11 is in the position in which the actuators for the pressure point elements are to be energized - but not which pressure point elements have to be fired.

FIG. 4 illustrates a detailed block diagram of the essential components of the swing mechanism shown in FIG. 3. As can be seen from FIG. 4, the position sensor 51 preferably comprises two signal amplifiers, namely A1 and A2; four operational amplifiers, namely OA1, OA2, OA3 and OA4; a light source L (light emitting diode); two photoelectric cells A and B and a slide V with two windows W1 and W2. The slide V is connected to the electromagnetic coil 31 of the linear motor 23 by a dashed line, which indicates that the slide V moves with the electromagnetic coil 31 and thus the position of the slide V follows the position of the print head 11. The light source L, the slider V and the photoelectric cells A and B are all positioned so that light from the light source L shines through the windows W1 and W2 and strikes the light detector surfaces of the photoelectric cells A and B. In other words, the windows W1 and W2 lie between the light source L and the photoelectric cells A and B, so that a window, namely W1, is sensitive to the light Liche area of the photoelectric cell A controls the amount of light and the other window W2 controls the amount of light incident on the photosensitive surface of the photoelectric cell B. The photoelectric cells are elongated, of the same size and are parallel to one another, as can be seen from FIG. 4. The windows W1, W2 are also elongated, of the same size and are parallel to each other. While the windows W1, W2 are the same size, only the length of the windows W1, W2 is the same as the length of the photoelectric cells A, B. The windows W1, W2 are somewhat wider than the photoelectric cells A, B. The windows W1 , W2 are also mutually offset and not laterally aligned like the photoelectric cells A, B, so that each window W1, W2 begins at the end of the other window and extends outwards in the opposite longitudinal direction.

The signal amplifiers A1 and A2 are each connected to one of the photoelectric cells A and B. The signal amplifiers A1 and A2 amplify the signals generated by the photoelectric cells. The operational amplifier OA1 works as a differential amplifier and generates an output voltage, the size of which corresponds to the difference between the voltage of the signals which are applied to the inverting and non-inverting outputs. The output of signal amplifier A1 is connected to the non-inverting input of differential amplifier OA1 and the output of signal amplifier A2 is connected to the inverting input of differential amplifier OA1. Accordingly, the output of differential amplifier OA1 is mathematically equal to the value of the voltage generated by photoelectric cell A minus the value of the voltage generated by photoelectric cell B (in Fig. 4, lower left part labeled A-B).

The output of the differential amplifier OA1 is connected to an input of the tilt comparator 57 and to an input of the pressure hammer trigger comparator 63.

The summator OA2 generates an output voltage, the size of which corresponds to the sum of the partial voltages applied to the two inputs, both of which can be described as non-inverting. The differential amplifiers OA3 and OA4 are components of the position sensor 51. The output of the signal amplifier A1 is connected to the input of the summer OA2 and the output of the signal amplifier A2 is connected to the second input of the summer OA2. The output of the summator OA2 (labeled A + B in Fig. 4) is connected to the inverting input of the differential amplifier OA3. A reference voltage VR is present at the non-inverting input of the differential amplifier OA3. The differential amplifier OA3 thus forms a trimming amplifier, which raises or lowers the output of the summator OA2 to a suitable voltage level. The output of the differential amplifier OA3 is connected to the inverting input of the differential amplifier OA4. The base voltage source VB is connected to the non-inverting input of the differential amplifier OA4. The output of the differential amplifier OA4 is connected to ground via the light source L.

As can easily be seen, the circuit formed by the summator OA2, the differential amplifiers OA3 and OA4 is an intensity control which regulates the illuminance generated by the light source L so that it is always constant. This control circuit compensates for fluctuations in the illuminance generated by the light source L, as well as gain fluctuations that occur equally in the two photoelectric cells A and B. The two photoelectric cells A and B should advantageously be identical, i.e. be coordinated so that most long-term fluctuations are the same and are canceled out by the explained control loop. The best way to match is by building the two photoelectric cells on the same plate and doping the adjacent surfaces of the common plate.

The toggle controller 55 shown in FIG. 4 contains the following components: a counter 71, a flip-flop module 73 in which data can be temporarily stored, a read-only memory 75 (ROM) and a digital-to-analog converter 77 Main controller 53 generates a plurality of output signals which are applied to the toggle controller 55. These control signals include reset pulses which are applied to the reset input of the counter 71, further flip pulses which are applied to the pulse counter input of the counter 71 and a parallel, selected, digital flip profile signal which is applied to the signal input of the flip-flop module 73 in the data stored temporarily. The input of the flip-flop module 73 is connected to the output of one of the stages of the counter 71. The address inputs of the read-only memory 75 are connected to the parallel outputs of the stages of the counter 71 and to the output of the flip-flop module 73. The signal outputs of the read-only memory 75 are connected to the digital signal inputs of the digital-to-analog converter 77 . The analog output of converter 77 is at the input of flip-flop comparator 57, as shown in FIG. 3 and described above.

Whenever a reset pulse occurs during operation, the counter 71 is reset to the starting position (for example zero). Thereafter, the counter 71 advances by 1 for each pulse when a toggle pulse is generated by the main controller 53. The selected digital tilt profile signal determines the tilt profile to be followed by the printhead 11 as it moves through the linear motor 23. In other words, the main controller 53 generates tilt profile selection signals that determine the profile (triangular, sinusoidal, sawtooth-shaped, and the like) that occurs when Hin - And moving the print head 11 must be followed. In all cases where the corresponding level of the counter 71 generates a pulse, the selected tilt profiles are gnale read into the flip-flop assembly 73 and stored there. The pulse generated by the counter 71 can occur, for example, when the counter 71 has been reset to zero. The selectable tilting profile signal stored in the flip-flop module 73, in conjunction with the counter stage output signals, forms the address to be applied to the read-only memory 75 at any time. Since the counter 71 continues each time a toggle pulse is generated by the main controller 53, the read-only memory address changes as the toggle pulses are generated by the main controller 53. The main controller 53 thus also controls the speed of the read-only memory address change by regulating the toggle pulse speed, which in turn regulates the speed of the change of the read-only memory output signals. As a result, both the printhead tilt profile and the speed at which the tilt profile is followed are controlled by the main controller 53. This means that a different parallel digital output signal is generated each time the read-only memory address changes. The parallel digital output signals generated by the read-only memory 75 are converted from the digital form into the analog form by the digital-to-analog converter 77. Thus, the signal applied by the toggle controller 55 to the toggle comparator 57 is an analog signal, the shape and rate of change of which is determined by the address on the read-only memory 75, which in turn is controlled by the main controller 53.

The tilt comparator 57 has a differential amplifier OA5. The output of the differential amplifier OA1 is connected to the inverting input of the differential amplifier OA5 and the output of the digital-to-analog converter 77 of the tilt regulator 55 is connected to the non-inverting input of the differential amplifier 0A5. The differential amplifier OA5 compares its two inputs in a conventional manner and generates a corresponding differential output signal.

The switching amplifier 59 consists of the following assemblies: two differential amplifiers OA6 and OA7, a filter 81, a current limiter 83, a pulse width modulator 85, two PNP transistors 01 and 02, two NPN transistors Q3 and Q4 and two resistors R1 and R2. The voltage source + V is connected via the filter 81 to the emitter connections of transistors 01 and Q2 and to the voltage input of current limiter 83. The collector of transistor 01 is connected to collector Q3 and the collector of transistor 02 is connected to the collector of transistor Q4 . The emitters of transistors 03 and 04 are connected to ground via resistors R1 and R2. The branch between the transistors 01 and Q3 is on one side of the electromagnetic coil 31 of the linear motor 23 and the branch between the transistors Q2 and Q4 on the other side of the electromagnetic coil 31. The output of the differential amplifier OA5 is connected to the inverting input of the differential amplifier OA6. The branch between the emitter of transistor 03 and resistor R1 is connected to the inverting input of differential amplifier OA7 and the branch between the emitter of transistor Q4 and resistor R2 is connected to the non-inverting input of differential amplifier OA7. The output of the differential amplifier OA7 is connected to the non-inverting input of the differential amplifier OA6 and to the control input of the current limiter 83. The output of the differential amplifier OA6 is connected to the control input of the pulse width modulator 85 and the output of the current limiter 83 to the switch-off control input of the pulse width modulator 85. The pulse width modulator 85 produces four outputs, one at the base of transistors Q1, Q2, Q3 and Q4.

As can easily be seen from the preceding description, the transistors 01 to 04 form the branches of a bridge circuit which regulates the polarity of the current flow through the electromagnetic coil 31 of the linear motor 23. In other words, transistors 01 and Q4, and Q2 and Q3 form pairs of switches that are in opposite operating states at a time (ie, transistors 01 and Q4 are on when transistors 02 and 03 are off and vice versa) unless all four transistors 01 to Q4 are switched off. When a pair of transistors, i.e. Q1 and 04, is switched on, current flows from the voltage source + V through the filter 81, through the transistor 01, through the electromagnetic coil 31 (in a certain direction), then through the transistor Q4 and finally through the resistor R2 to earth. In the event that the other transistor pair 02 or 03 is switched on, current flows from the voltage source + V through the filter 81, through the transistor Q2, through the electromagnetic coil 31 (now in the opposite direction), then through the transistor Q3 and finally through resistor R1 to ground.

The respectively open and closed switching states of the transistors Q1 to Q4 are regulated by the high-low states of the outputs of the pulse width modulator 85. The HL states of the outputs of the pulse width modulator 85 are in turn regulated by the polarity of the output of the differential amplifier OA6. In the event that the output of the differential amplifier OA6 is positive, the outputs of the pulse width modulator 85 are switched such that one pair of transistors (01 and 04 or Q2 and 03) is switched on and the other pair is switched off. In contrast, in the event that the output of the differential amplifier OA6 is switched to negative, the outputs of the pulse width modulator 85 are switched such that the second pair of transistors is switched on and the first pair is switched off.

Because the polarity of the output of the differential amplifier OA6 depends on whether the current feedback signal developed by differential amplifier OA7 (which is determined by the difference in voltage drops across resistors R1 and R2) is greater or smaller than the output of differential amplifier OA5, the ratio between these two voltages determines the polarity of the current flow through the electromagnetic coil 31 of the linear motor 23. In the event that the position deviation voltage which occurs at the output of the differential amplifier OA5 is higher than the voltage at the output of the differential amplifier OA7, the current flow direction is such that the electromagnetic coil 31 pushes the slide V into a Direction drives that changes the voltage value AB in such a way that the output of the differential amplifier OA5 increases. It is accordingly the position deviation voltage appearing at the output of the differential amplifier OA5 under the voltage at the output of the differential amplifier OA7, the Stromfliessrichtun ^g so that the coil moves the slider V (and thus the print head 11) in a direction that the Voltage value AB changes in such a way that the output pulse at the differential amplifier OA5 decreases.

The output of the differential amplifier OA6 not only regulates the direction of the current flow through the electromagnetic coil 31 in the manner just described, but also the magnitude of the current flow. More precisely, the size of the output at the differential amplifier OA6 regulates the width of the switching pulses which are applied to the switched-on transistor pair. Since the width or switch-on time of the transistor switches determines the size of the current applied to the electromagnetic coil 31, the size of the output at the differential amplifier OA6 regulates the size of the current applied to the electromagnetic coil 31. The current limiter 83 is provided in order to maximally determine the amount of current that can be applied to the electromagnetic coil, so that destruction of the electromagnetic coil and / or the transistors 01 to Q4 is prevented.

The print hammer trigger controller 61 consists essentially of the following modules: the flip-flop module 91, in which data can be temporarily stored, and a digital-to-analog converter 93. The main controller 53 generates digital signals in parallel which indicate the print hammer trigger positions. The digital signals are read into the flip-flop module 91 and stored there, whenever the main controller 53 generates a memory signal. The digital output of the flip-flop module 91 is connected to the digital input of the digital-to-analog converter 93 and is converted there from digital form to analog form. The analog form of the print hammer trigger position signals are applied to the second input of the print hammer trigger comparator 63.

The print hammer trigger comparator 63 comprises the following essential elements: a guide circuit 95 and a differential amplifier OAB. The signals A-B generated by the position sensor 51 are applied via the guide circuit 95 to the non-inverting input of the differential amplifier OA8. The analog signals generated by the digital-to-analog converter 93 of the print hammer trigger controller 61 are applied to the inverting input of the differential amplifier OA8. The differential amplifier OA8 compares its two input signals by differentiation and generates another output signal, which is connected to the print hammer release circuit 65 shown in FIG. 3 and already described. The guide circuit 95 provides part of the path for the actual position signal to compensate for the print hammer flight time. In practical operation, a time advance of the actual print hammer position signal is compared to a signal representing the desired print hammer trigger position. In the event that the two signals match, the state of the output on the differential amplifier OA8 changes and forms a print hammer trigger pulse for the print hammer trigger circuit 65.

As can be seen from the above description, the invention represents a highly precise oscillation mechanism which is particularly suitable for matrix line printers and which precisely controls the movement of the print head 11 and the triggering of the print actuation devices. The invention uses a relatively rigid, tuned flexure system that operates near its resonant vibration frequency and a relatively strong linear motor with a vibrating solenoid to minimize printhead travel time. The invention is therefore ideally suited for use in matrix line printers which operate at high speed. The electromagnetic coil 31 is preferably completely reversed when the last point position is reached. The full excitation of the linear motor 23 in connection with the energy stored in the bending elements 13, 15 and 27, 29 leads to extremely short cycle times. In one embodiment of the invention, the cycle time is 3 milliseconds. In contrast to the embodiment described in U.S. Patent 4180766, which requires several cycles before printhead movement increases to operating speed, in the embodiment according to the present invention, printhead movement increases to operating speed within a quarter.

Claims (12)

1. Swinging mechanism for straightline, uniform movements to and fro of a carrier (11 ) or similar device by means of a linear drive for a printing mechanism that can be moved, in line direction, in front of a recording carrier (21) shiftable vertically relative to the line direction, with the carrier (11) being supported by parallel bending elements (13, 15) retained in a frame (16), the linear drive consisting of an electrically powered linear motor (23), arranged in a housing (25) and featuring magnetic means and a movable electric solenoid coil (31) with changeable polarity, and the electric solenoid coil (31 ) being electrically connected to an electricity supply and means to control polarity and magnitude of current flow, characterized by the housing (25) being supported by separate, likewise retained, parallel bending elements (27, 29) to match the resonant vibration frequency of the linear motor (23) and housing bending elements (27, 29) combination to the resonant vibration frequency of the carrier (11) and bending elements (13, 15) of the carrier (11) combination, and a connecting element (33) which is coupled to the electric solenoid coil (31) being provided between the electric solenoid coil (31) and the carrier (11).

2. Swinging mechanism according to claim 1, characterized by the spring constant of the bending elements (13, 15) supporting the carrier (11) being selected so that the resonant vibration frequency of the carrier (11) and bending elements (13, 15) combination largely agrees with the to and fro movement frequency.

3. Swinging mechanism according to claims 1 and 2, characterized by the control means for the polarity and the magnitude of the current flow in the electric solenoid coil (31 ) consisting of a position sensor (51 ) sensing the position of the carrier (11), means for the continuous generation of an actual position signal, means for the continuous generation of a desired position signal, means for the comparison of the actual position signals with the desired position signals, means for the generation of variation signals depending on the magnitude of the differential between the actual and desired values as well as means for the control of the currentflow in the electric solenoid coil (31) in keeping with polarity and magnitude.

4. Swinging mechanism according to claims 1 to 3, characterized by the means for the continuous generation of a desired position signal featuring a main controller (53) to generate the desired position signals digital-fashion and a digital/analog converter (77), with the analog type actual position signals being compared together with the analog desired position signals by analog signal means.

5. Swinging mechanism according to one or several of the claims 1 to 4, characterized by the means for the control of the current flow in the electric solenoid coil (31) including a pulse width modulator (85).

6. Swinging mechanism according to claim 5, characterized by the means for the control of the current flow in the electric solenoid coil (31) featuring a bridge circuit containing four switches (Q1, Q2, Q3, Q4) with always one switch being arranged in one bridge and the electric solenoid coil (31) being arranged in the bridge diagonal, and one bridge being connected to the power source (+V), the pulse width modulator (85) generating four output control signals on the four switches (Q1 to Q4).

7. Swinging mechanism according to one or several of the claims 1 to 6, characterized by the position sensor (51) for the position of the carrier (11) featuring a light source (L), one pair of photocells (A, B) associated with the light source (L) and a slide (V) having one pair of windows (W1, W2) and being connected with the carrier (11).

8. Swinging mechanism according to claim 7, characterized by the photocells (A, B) consisting of longitudinal approximately equal-sized photoelectric cells.

9. Swinging mechanism according to claims 7 and 8, characterized by the windows (W1, W2) in the photocells (A, B) being approximately of equal size, of longitudinal shape and off set relative to each other in longitudinal direction.

10. Swinging mechanism according to claims 7 to 9, characterized by the windows (W1, W2) extending in the direction of the longitudinal photocells (A, B).

11. Swinging mechanism according to one or several of the claims 1 to 10, characterized by the position sensor (51 ) featuring a differential comparator connected to the photoelectric cells (A, B) with the output signal constituting the actual position signal based on the voltage differential.

12. Swinging mechanism according to one or several of the claims 1 to 11, characterized by the position sensor (51) being connected with a light control loop connected to the outputs of the photoelectric cells (A, B) and the light source (L).

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