DE3825232C1 - Method and circuit arrangement for producing information on the type of a print head - Google Patents

Abstract

A method and a circuit arrangement are described for producing information which indicates the type of print head (18) which is fitted in a printer and contains at least one printing element (86, 88, 90). The actuator of the printing element (86, 88, 90) has an electrical resistance which is detected via an evaluation circuit. This resistance is assigned to one of a plurality of resistance zones which correspond to different types of print head. The evaluation circuit produces as the information a type signal (40a, 40b, 40c) as a function of the assignment made. The type signal (40a, 40b, 40c) is made available to a downstream controller which can supply the various types of printheads (17, 18) with the respective matched control signals. The invention can be used on virtually all types of printheads whose printing elements are operated via electrical or electromechanical actuators and in consequence have an electrical resistance. <IMAGE>

Description

The invention relates to a method for generating information that is of the type present in a printer which indicates printhead, the at least one printing element contains, the actuator has an electrical resistance. The invention further relates to a circuit arrangement for through conduct the procedure.

Printers are used in electronic data processing systems to output text, data and image information puts. Transferring print characters to a carrier, at for example paper, is done by a printhead. Newer Printers are characterized by the fact that they have printheads under can contain different types in a printer housing. Such a printer is e.g. B. in DE-OS 35 11 386 ben. With this device, the printheads of a printing sta tion to be replaced, one printer several such Print stations can contain. The printer has here a simple basic housing that is very economical in large large quantities can be produced. Depending on the application case the basic housing with different printheads equipped, whereby an individual equipment request of the Customers only have to be considered during final assembly. There can be a large variety of printers and a ho he economic efficiency of production can be achieved. equipment of this type, e.g. B. as passbook printer, till receipt printer ker or the like.  

There are a number of printing methods that differ functional principles and designs of printheads have leads. The printheads are used to transmit the print signs on the carrier a variety of printing elements that according to the different printing processes are trained. Among these has the mosaic printing process acquired particular importance. With this procedure, that is Drawing patterns made up of individual color dots in a mosaic set, which are generated by the printing elements. At a Such a printing element exists in ink mosaic printing processes from a nozzle that when driving a piezoelectric Actuator with an electrical pulse an ink drop fen sprayed on the data carrier, there bil a color point det. By putting together many individual color dots in an egg The print symbol is created on a grid. In another ver drive, the needle printing, the individual printing elements are as Needles trained. These are made by an electromechani rule actuator due to the force of a current deflected flow and press a ribbon against the Print carrier, which also makes a punctiform drawing ster emerges. Finally, the thermal printing process ren mentioned, in which the pressure element as an actuator contains electrical resistance that occurs when power is supplied heats up. Dot-like printing is done using a melting ribbon Transfer characters to the print carrier or directly on one generated heat-sensitive recording medium.

The print head must be used to carry out the printing process Control signals are supplied that have a specified value have area and correspond to tax parameters. This tax Parameters are generated in a control device which controls the information to be printed is supplied. Important tax para meters are z. B. the selection of the printing element for printing a mosaic point or a combination of printing elements for  Imprinting a character and the amount of energy that z. B. in Form electrical energy to the respective pressure elements Carrying out the printing process must be supplied. A Another important control parameter is the timing the printing process and its duration. Through time correct control of the printing process depends on the Relative movement between the printhead and the carrier of the The location of the print mark on the carrier is determined. Various Types of printheads differ in the tax para meters. Different types of printheads in a printer are used, so are those from the Steuereinrich to provide control parameters to the type of printing head to adjust. Because the control parameters of the different Printhead types are known, it is possible to control direction in such a way that all control parameters of the in contains a printhead type intended for a printer and these are available on demand. The control parameters can e.g. B. as Data stored in a memory or via controllable switching circles can be preset. So that the control device one Printhead the control parameters usable for it ready However, it needs information about the type of the print head to be controlled.

This can be done in such a way that a trained Be the operator by means of a manual check of the type or type of the printhead and this information by Be actuate a coding switch of the control device. This procedure entails the risk of incorrect operation as a result incorrect identification of the printhead or incorrect Switch setting in itself. In addition, they are mechanically constructed tive measures required to prevent an accidental or un to exclude authorized access to the coding switch. There it would be desirable to transfer information via ver the type of the printhead automatically by the printer cause to work incorrectly with the printer high probability to exclude.  

From DE 33 34 980 A1 a method is known in which the Identity of a type wheel present in a cassette based on of a display section can be determined. The ad section has a resistance part, the electrical Wi the status is used for the identity check. For scanning the resistance of the special sensors are provided, which with ent speaking contacts of the resistance part in touch contact to be brought. The required design dimension Acceptances are complex and have to be made on a special request application, for example for type wheel printheads be cut.

EP 02 17 043 A1 also describes a method for ascertaining known manufacturing defects in thermal printheads. Here the voltage drop, which is caused by the heating resistance of a pressure element causes flowing current. The detection of the type of a printhead is in this process not possible.

It is an object of the invention to provide a method or a circuit arrangement type that automatically entered the type of in a printer built printhead and this information to after gives orderly controls.

This object is solved by the features of claims 1 and 7, respectively.

As a differentiator between different pressures The electrical resistance of a pressure element becomes head types used. This resistance is characteristic of one certain type of printhead. For example, a printing element of a tin ten beam print head with a piezoelectric actuator high resistance with a capacitive resistor compo nente, while the printing element of a wire dot printhead, the contains a coil with a low resistance value inductive component. The resistance value of Druckele elements of thermal printheads is generally between these values. Also the resistance value of printheads ner class, e.g. B. the class of needle printheads, one certain embodiment or type of a printhead charak terize. So are the coils for actuating the Druckele elements of needle printheads with a large needle stroke or needle printheads with a small needle stroke are designed differently, d. H. also the resistance values of the corresponding coils can be evaluated as a distinguishing feature.

The resistance of the printing elements of different printheads ten is generally well known from the outset or can be determined by a simple resistance measurement.  

The resistance value of the pressure elements of a given pressure Head type is within a defined tolerance range th resistance range. The invention uses this knowledge nis by the resistance value of a pressure element of a printhead to be checked and this one of the assigned defined resistance ranges. That was done Assignment is indicated by a type signal. The resistance value of a printing element can easily over the same current path through which the electrical energy to the Pressing the pressure element is supplied, who determined the. In this case there are no further design measures such as additional contacts or signal lines, required on the printhead, but it can commercially available printheads can be used. This results in a significant economic advantage. The invention can be applied to practically all types of printheads the one whose pressure elements are electrical or electromecha African actuators are actuated and therefore an elec trical resistance.

When determining resistance, the opponent also has status value praktische practical information as recognition information. This value is to be interpreted as meaning that a certain pressure ment, the resistance value of which is to be determined, in printing head does not exist. The presence or absence of Being a pressure element can be a certain type of Characterize the printhead. For example, a 7-pin printhead distinguished from a 9-pin printhead the resistance value of the eighth or the nine th pressure element is determined. If this is infinite, so this indicates a 7-segment type print head.

In conjunction with a control device that the various which control parameters of the ar intended for a printer  contains printheads, it is possible to control parameters depending on the type signal to sit down. By doing so, the Total control effort is low, as with a single Control device several different types of printheads can be controlled. When replacing printheads hence also the replacement of the control device as it is would otherwise be required, eliminating the need to operate the Printer is easier and therefore safer.

A preferred development of the invention is characterized in that a measuring resistor is provided for determining the resistance, which is flowed through by a current dependent on the resistance value of a pressure element. The water resistance is connected in series to the resistance of the actuator of the pressure element, the resistance value of which is to be determined. Both resistors that flow through the same current thus form a voltage divider. The voltage drop U at the measuring resistor is used as a measure of the resistance value of the pressure element and fed to a downstream evaluation circuit. The voltage drop U there results in U = V · RM / ( R + RM ), where V is the supply voltage, R is the resistance of the pressure element and RM is the measuring resistor.

According to a further embodiment of the invention, at least two pressure elements each one in the forward direction be driven decoupling diode connected in parallel. This paral Oil circuit is connected in series with the measuring resistor. With this measure, several printing elements can be one or interconnect several printheads without reaction, d. H. between the interconnected pressure elements the barrier layer of a decoupling diode is effective, which prevents current flow between the pressure elements.  

The decoupling diodes are connected so that the to the fixed set the resistance value of the pressure elements required Test current flow in the forward direction of the decoupling diodes can. Overload the test currents of the affected pressure elements like to flow and flow through the measuring resistor, one Voltage is generated. By connecting several Print elements will have a higher sensitivity when Evaluation of the voltage achieved.

In a development of this, in a printing station, the printheads with a different number of prints can accommodate elements, at least one pressure element that to a printhead with a lower number of printing elements hears, as well as at least one pressure element that only one Printhead with a higher number of print elements belongs to which respective decoupling diode switched. In a printing state on, the z. B. both a needle print head with 7 needles as who can also hold a needle print head with 9 needles then the printing elements number 6 and num mer 8 connected to each other via the decoupling diodes. Is the print station is equipped with the 9-needle print head, so addie the test currents in the measuring resistor. However, if as Printhead in the printing station a 7-needle printhead existing that is, the space of the ninth pressure element is not be sets, and it becomes only the test current of the sixth Druckele evaluations. This makes it possible to print heads yourself with different numbers of similar printing elements easy way to distinguish.

In a further embodiment of the invention, that in the signal path between the measuring resistor and the Pressure element of the emitter-collector section of a switchboard sistor is connected, which is based on a test signal is activated. The switching transistor is here  by the test signal between the states "lock" and "Conduct" switched back and forth. In the "lead" state flows about the resistance of the pressure element of the test current, which is used for Determination of the resistance value serves. In this condition are the pressure elements at rest, d. H. the Druckele elements are not supplied with current impulses Trigger the printing process and falsify the test current could. In the "blocking" state, no test current can flow through the Pressure elements flow. The printing elements are then ready receive the current pulses required for printing.

A further development of the circuit arrangement according to the Erfin is given by the fact that to generate the type signal an evaluation circuit is provided which has at least one Threshold circuit contains, the threshold of a be matched range of resistance associated with a pressure head type corresponds. The threshold circuit compares them Voltage corresponding to the resistance of a pressure element, with a reference voltage. This forms the threshold at whose exceeding the output signal of the threshold scarf device is switched. The reference voltage is chosen so that the two states of the output signal the threshold circuit clearly a resistance range and thus one can be assigned to a specific type of printhead. On hand of the output signal can thus a maximum of two types of Printheads can be distinguished.

One is appropriate for recognizing several types of printheads to use a larger number of threshold circuits. Here to be able to output the threshold signals in advantageously logically linked. This can be done in that the output signal of each Threshold circuit conjunctively with the inverted output signals of the threshold circuits with a higher threshold  is linked to a type signal, and that the output signal the threshold circuit with the highest threshold value directly or output as a type signal via a non-inverting gate becomes. This measure makes every type of printhead assigned a type signal. The logical link of the off output signals of the threshold circuits causes only egg nes of the type signals has the binary value 1, while all others Type signals have the binary value 0. The signaling of a certain type of a printhead with digital coding thus achieved in a particularly simple manner.

Embodiments of the invention will be described with reference explained on the drawing. It shows

Fig. 1, various functional units of a printer in block form,

Fig. 2 modules of a control means for dently tion of printheads

Fig. 3 shows a circuit arrangement for recognizing under different types of printheads, and

Fig. 4 waveforms and states of the circuit arrangement according to FIG. 3 over time.

In FIG. 1, various functional units are shown of a printer with a plurality 10, 12, 14 containing designated printing stations. Each of these printing stations 10 , 12 , 14 can accommodate a printhead which is mechanically and electrically detachably connected to the respective printing station and can be replaced. The printing stations 10 , 12 , 14 are designed so that they can accommodate different types of print heads. Thus, in Fig. 1, the printing station 10 is occupied by a print head 16 which is formed as an ink mosaic printer. At the printing station 12 , a printhead 18 is connected, which works according to the dot-matrix method and has nine printing elements. The printing station 14 receives a dot-matrix print head 20 , which has seven printing elements.

The printheads 16 , 18 , 20 are supplied by a control device 22 with printhead-specific control parameters via the signal paths 24 , 26 , 28 . The control device 22 receives the information to be printed via a signal path 30 from a higher-level controller (not shown) of the printer or from an external controller.

A circuit arrangement for print head detection 32 receives electrical signals 34 , 36 , 38 from the print stations 10 , 12 , 14 , which uniquely characterize the type of print heads 16 , 18 , 20 present in the print stations 10 , 12 , 14 .

The circuit arrangement for print head detection 32 forms from the electrical signals 34 , 36 , 38 a type of print head characterizing type signal 40 , the device 22 Steuereinrich is supplied. This enables the various types of print heads 16 , 18 , 20 to be supplied with the control parameters typical of each print head.

In Fig. 2, various assemblies of the control device 22 are shown in addition to other. The designations for modules already described in FIG. 1 have been retained. Via the circuit arrangement for print head detection 32 , the type signal 40 is made available to various assemblies. The different types of print heads 18 , 20 are controlled via a multiplexer module 50 . This switches one of the print heads 18 , 20 ready for operation depending on a multiplexer signal 52 . The multiplexer signal 52 is also generated by a higher-level controller that coordinates the printing processes of different printing stations. A driver block 54 provides the pulses required to actuate the individual pressure elements of the printheads 18 , 20 . For this purpose, the driver module 54 is supplied with control parameters specific to the printhead to be written. The printing elements for printing a character or a mosaic point are selected indirectly via character generators 56 and 58 . In these, the addresses of the printing elements are stored in the printhead in character sets, which are to be actuated to generate a specific printing character. The character generator 56 is used to generate print characters for a mosaic print head with 9 Druckele elements and the character generator 58 for one with 7 print elements. The information to be printed is received by the character generators 56 , 58 via a signal 60 from the superordinate control.

A data multiplexer 62 switches the data of one of the character generators 56 , 58 to the driver module 54 . The switching state of the data multiplexer 62 is controlled by the type signal 40 .

The energy for actuating the pressure elements selected by the character generator is taken from a controllable current source 64 . It delivers a defined current at its output, the strength of which is also controlled via the type signal 40 .

The triggering of the printing process and its duration is controlled by a controllable clock module 66 . It causes the power supply to the Druckelemen th on or off via the driver block 54th Both the duration of the current supply and the temporal position of the current pulses with respect to a position signal, which indicates the relative position between the print head and the recording medium, can vary with different types of print heads. For this reason, these time parameters are generated depending on the type signal 40 and output to the driver module 54 .

Furthermore, the type signal 40 is fed to a display unit 68 . This indicates the type of print heads 18 , 20 present in a printer via signal lamps 70 , 72 , 74 . The type signal 40 can also be output via an adapter 76 in order to be further evaluated at another point. It is thus possible, depending on the type signal 40 , to monitor and control the feed of the print carrier or the ribbon feed. Furthermore, other control devices which, for example, control the relative movement between the print head and print carrier in the row and column direction, can evaluate the type signal 40 in order to adapt control processes to the type of print head present in the printer.

In Fig. 3, a circuit arrangement is shown which enables automatic detection of different types of printheads. The designations of FIGS . 1 and 2 have been retained provided the same assemblies have been used. Via the multiplexer module 50 , a print head 17 , which works according to the thermal printing method, and the wire print head 18 are connected to the supply voltage V. The multi plexerbaustein 50 is ert gesteu via the multiplexer 52nd When the print heads 17, 18 are shown from the plurality of printing elements three printing elements. In the print head 17 , these are the printing elements 80 , 82 , 84 , each of which is preceded by a diode 81 , 83 , 85 , which prevents a current distribution between printing elements connected in parallel; in the printhead 18 , the printing elements 86 , 88 , 90 are shown, to which the diodes 87 , 89 , 91 are connected in a corresponding manner. A diode 92 switched in the reverse direction serves to reduce voltage pulses which can arise as a result of induction when the pressure elements 86 , 88 , 90 are switched off. A diode 93 switched in the reverse direction is also assigned to the print head 17 . This is not absolutely necessary with a thermal print head, since its print elements show ohmic behavior. Since, instead of the thermal print head 17 , a dot-matrix print head can also be used, the print elements of which have inductive behavior, the diode 93 is also provided here.

In order to be able to electrically detach the print heads 17 , 18 from the printer housing, connecting terminals 94 , 96 , 98 , 99 and 100 , 102 , 104 , 105 are provided. The printing elements 86 , 88 , 90 of the needle printhead 18 contain small electromagnets which, after opening with a current pulse, deflect a movable needle that generates a halftone dot on a print carrier via an ink ribbon.

The needles of the printing elements 86 , 88 , 90 are arranged vertically one above the other, so that when the print head fes 18 is moved transversely to a printing medium there are rasterized characters when the printing elements 86 , 88 , 90 are actuated. The driver module 54 together with the controllable current source 64 delivers the required current pulses. The selection of the printing elements, the temporal position and the duration of the current pulses are specified by the control device 22 as further control parameters 106 . In the print head 17 , the printing elements 80 , 82 , 84 consist of small electrical heating resistors that heat up when the power is supplied and transfer punctiform print characters to the print medium via a melt ribbon. Here too, the print head 17 is supplied with current pulses from the driver module 54 and the controllable current source 64 .

To the interconnected cathodes of the diodes 83 , 89 and to the cathodes of the diodes 85 , 91 , a decoupling diode 108 and 110 are connected with their anode connection, the cathode connections of which are brought together at a current summing point 112 . The current sum point 112 is connected to the collector port of a switching transistor 114 of the npn-conductivity type, the base of which is supplied with a test signal 115 . The emitter connection of the switching transistor 114 is connected via a measuring resistor 116 to the reference potential and directly to the non-inverting inputs of a first threshold circuit 118 , a second threshold circuit 120 and a third threshold circuit 122 . A first reference voltage 124 , a second reference voltage 126 and a third reference voltage 128 are fed to the inverting inputs of the threshold value circuits 118 , 120 , 122 . The reference voltage 124 has the lowest voltage value and the reference voltage 128 the highest. The threshold circuits 118 , 120 , 122 each carry a low-level signal at their output if their associated reference voltage 124 , 126 , 128 is greater than the voltage at their non-inverting inputs. If the voltage exceeds the level of one of the reference voltages 124 , 126 , 128 , the affected threshold circuit 118 , 120 , 122 switches its output signal to high level. The low level is assigned to binary value 0 and the high level to binary value 1.

The output signal of the threshold circuit 118 is fed to an AND gate 130 at its non-inverting input. It has two further, however inverting inputs, to which the output signal of the threshold circuit 120 or that of the threshold circuit 122 is applied. The output signal of the threshold circuit 120 is fed to a two-th AND gate 132 at its non-inverting input. Another inverting input is connected to the output of the threshold circuit 122 . Finally, a third gate 134 is provided in the circuit arrangement, which works as a non-inverting driver circuit, and whose input is connected directly to the output of the threshold circuit 122 . The gates 130 , 132 , 134 generate the type signals 40 a , 40 b , 40 c .

The mode of operation of the circuit arrangement for printhead recognition is described below. First, it is assumed that the multiplexer module 50 is controlled via the multiplexer signal 52 so that the print head 17 is connected to the supply voltage V. The printhead 17 is thus fourth and a test phase can follow, in which the type of printhead is determined. For this purpose, the switching transistor 114 is turned on at its base via the test signal 115 . At the same time, the driver module 54 is controlled so that the switches indicated in FIG. 3, which supply the pressure elements 80 , 82 , 84 with current, are open. The signals for controlling the switching transistor 114 and the driver module 54 are provided by a higher-level controller, not shown.

Via the current path, formed from the pressure element 82 , the diode 83 and the diode 108 , a current flows to the current collecting point 112 , which is added to the current flowing through the pressure element 84 , the diode 85 and the diode 110 , and via the Switching transistor 114 and the measuring resistor 116 is derived from ground. The strength of the current depends in wesent union on the level of the supply voltage V , the size of the resistance of the pressure elements 82 , 84 and the measuring resistor 116 . This current drops a voltage across the measuring resistor 116, which voltage is supplied to the threshold value circuits 118 , 120 , 122 . The threshold circuits 118 , 120 , 122 compare this voltage value with the reference voltages 124 , 126 , 128 supplied to them and switch their output signal to high level when the voltage across the measuring resistor 116 is greater than the respective reference voltage 124 , 126 , 128 .

The resistance of the pressure elements 82 , 84 is known and varies only in a very small range. Thus, the current through the measuring resistor 116 and thus its voltage drop is characteristic of the type of pressure head 16 tested. The reference voltages 124 , 126 , 128 are accordingly assigned to a certain range of the voltage across the measuring resistor, which characterizes a certain type of printhead. They are chosen so that they are at the lower limit of such a voltage range.

It is assumed that the current voltage across the measuring resistor 116 is slightly larger than the reference voltage 126 , so that the threshold value circuit 120 sets a high level at its output, which corresponds to the binary value 1. Since, as already mentioned, the reference voltage 124 is lower than the reference voltage 126 , the output signal of the threshold circuit 118 also has the binary value 1. However, the downstream AND gate 130 is supplied with the output signal of the threshold circuit 120 inverted, so that the result of the AND Linking is logic 0, and the AND gate 130 outputs a type signal 40 a with binary value 0. Furthermore, it is assumed that the reference voltage 128 is greater than the voltage across the measuring resistor 116 . Then the output signal of the threshold circuit 122 is logic 0 and thus also the type signal 40 c of the gate 134 . The output signal of the threshold value circuit 122 is fed to the AND gate 132 in an inverted manner, so that together with the binary value 1 of the threshold value circuit 120 the AND condition is fulfilled and the AND gate 132 generates the type signal 40 b with a binary value 1 at its output. The type signal 40 b is here assigned to the print head type "thermal print head". The binary value 1 indicates that the ge printhead 17 is a thermal printhead. Due to the special logical combination of the output signals of the threshold value circuits 118 , 120 , 122 , it is achieved that only one of the type signals 40 a , 40 b , 40 c can have the binary value 1. Through this type of type signal generation, the type of a print head is displayed in a simple and clear code. However, other forms of coding are also conceivable, such as. B. a serial coding by converting the voltage across the measuring resistor 116 into a frequency, or a PCM closures u. The binary information is then to be decoded in a known manner by the control device 22 and can then be evaluated. It is also conceivable that the output signals from the threshold circuits 118 , 120 , 122 are interpreted as bit positions of a binary word. In this case, the gates 130 , 132 , 134 can be omitted. If the voltage across the measuring resistor 116 exceeds the first reference voltage 124 , the binary word then has the value 1, when the reference voltage 126 is exceeded the value 3 and when the reference voltage 128 is exceeded the value 7.

The test phase is ended in that the switching transistor 114 is switched to the blocking state via the test signal 115 . The printing elements 80 , 82 , 84 of the print head 17 can then be actuated by current pulses from the driver module 54 and can carry out the printing process. After completion of the printing process, the print head 17 is disconnected from the supply voltage V. Now the print head 18 can be switched to work via the multi plexer module 50 . Here, too, the type of the printhead is determined in the manner described in a test phase which is provided before the start of printing.

The head detection circuit with the components 124 to 134 can be expanded analogously in accordance with the number of print heads to be recognized. It is also possible to recognize printheads that have the same resistances of the printing elements, but whose number of elements differs. A 7-pin printhead and a 9-pin printhead are given here as examples. For printhead detection, the anode of diode 108 is connected to a printing element that is present in both printhead types, e.g. B. to the printing element number 7. The anode of the diode 110 is switched to the printing element, which is only available when printing head with a higher number of needles, for. B. to the print element number 8. If the print station is equipped with a 9-needle print head, the total current of the parallel connected print elements numbers 7 and 8 flows in the measuring resistor 116. However, if a 7-pin print head is available in the print station, the test current, which is evaluated for printhead detection, is halved.

It is also possible to connect a to a threshold circuit Apply reference voltage of 0 volt. That can't do it presence or defect of a printhead or print elements are recognized and signaled.

In FIG. 4, over the time t, the various signals and states of the circuit arrangement shown in FIG. 3. By supplying the supply voltage V via the multiplexer module 50 , the print head 17 or the print head 18 are switched from the rest position to the work state, which is indicated in FIG. 4 by the states "OFF" or "ON". After turning on the print head 17 , he recognizes the type of print head. For this purpose, the test signal 115 is set to the binary value 1 for a fixed duration. During this time, the driver module 54 remains switched off, ie the print elements of the print head 17 are not supplied with current pulses.

During the test phase, the resistance of the print elements 82 , 84 of the print head 17 is determined, and the type signal 40 b assumes the binary value 1 for the duration of the test. The test process is ended by resetting the test signal 115 to the binary value 0, as a result of which the type signal 40 b also assumes the binary value 0. Now he can follow the actual printing process, which is controlled by the driver module 54 .

In the same way, the type of print head 18 can also be determined, for which the steps described above are to be carried out. The type of printhead 18 is indicated here by the binary value 1 of the type signal 40 c , which is the type signal for needle printheads.

Claims (12)

1. A method of generating information indicating the type of a printhead present in a printer that contains at least one printing element, the actuator of which has an electrical resistance, characterized in that the resistance is determined and is assigned to one of several resistance ranges, which under correspond to different types of printheads, and that a type signal ( 40 , 40 a , 40 b , 40 c ) is generated as information depending on the assignment made. 2. The method according to claim 1, characterized in that in printheads ( 16 , 18 ) with a plurality of printing elements ( 80 , 82 , 84 , 86 , 88 , 90 ), the resistance only for a part of these printing elements ( 82 , 84 , 88 , 90 ) is determined. 3. The method according to claim 1 or 2, characterized in that a control device ( 22 ) depending on the type of the print head to be controlled ( 16 , 17 , 18 , 20 ) different control parameters, it can testify, and that the head to the respective print ( 16 , 17 , 18 , 20 ) appropriate control parameters are set by the type signal ( 40 , 40 a , 40 b , 40 c ). 4. The method according to any one of claims 1 to 3, characterized in that in the case of different types of print heads ( 17 , 18 , 20 ) elements for selecting the print elements are accessed, each of which is assigned to a type of print head. 5. The method according to any one of the preceding claims, characterized in that the type signal ( 40 40 a , 40 b , 40 c ) also for controlling the print carrier feed and / or the ribbon feed and / or the relative movement between the print head ( 16 , 17 , 18th , 20 ) and print carrier is evaluated. 6. The method according to any one of the preceding claims, characterized in that the type signal ( 40 ) is shown on. 7. Circuit arrangement for performing the method according to any one of the preceding claims, characterized in that a measuring resistor ( 116 ) is provided for determining the resistance, which is flowed through by a current dependent on the resistance of a pressure element ( 82 , 84 , 88 , 90 ) . 8. Circuit arrangement according to claim 7, characterized in that at least two pressure elements ( 82 , 84 , 88 , 90 ) are each connected in series with the decoupling diode ( 108 , 110 ) in series with the measuring resistor ( 116 ). 9. Circuit arrangement according to claim 8, characterized in that at a printing station ( 10 , 12 , 14 ) which can accommodate printheads with a different number of printing elements, at least one printing element ( 88 ) leading to a printhead with a low number of printing elements belongs, and at least one printing element ( 90 ), which only belongs to a printhead with a higher number of printing elements, are connected to the respective decoupling diode ( 108 , 110 ). 10. Circuit arrangement according to one of claims 7 to 9, characterized in that in the signal path between the measuring resistor ( 116 ) and the pressure element ( 82 , 84 , 88 , 90 ) the emitter-collector path of a switching transistor ( 114 ) is switched GE, which is controlled by a test signal ( 115 ) at its base. 11. Circuit arrangement according to one of claims 7 to 10, characterized in that for generating the type signal ( 40 , 40 a , 40 b , 40 c ) an evaluation circuit is provided which contains at least one threshold circuit ( 118 , 120 , 122 ), whose threshold value is assigned to a specific resistance range that corresponds to a type of printhead. 12. Circuit arrangement according to claim 11, characterized in that the output signal of each threshold circuit ( 118 , 120 , 122 ) is conjunctively linked to the inverted output signals of the threshold circuits with a higher threshold to form a type signal ( 40 a , 40 b , 40 c ), and that the output signal of the threshold circuit ( 122 ) with the highest threshold value is output directly or via a non-inverting gate ( 134 ) as a type signal ( 40 c ).