CH635030A5 - METHOD AND DEVICE FOR DELETING UNWANTED CHARACTERS IN OPTIONAL PRINTERS. - Google Patents

Description

The invention relates to a method and an apparatus for erasing unwanted printed characters, e.g. Printing errors, in serve printers by overprinting with a correction medium.

In the past, unwanted characters were erased using an eraser and stencil. The introduction of overprinting for correction either with a masking material that covers the unwanted character or with a sticky tape that allows the unwanted character to be lifted off the paper was a great relief. The correction by overprinting is much faster and cleaner than the old method and generally results in less visible correction points in the original.

Despite these advantages, many modern typewriters do not have a correction device that works with overprints. One possible reason for this is that the precise alignment of the characters on machines that operate at somewhat higher speeds, e.g. the printing wheel typewriters, is not sufficient to allow a complete eradication of the undesired character. Typewriter and typewriter typewriters can generally be adjusted so that overprinting a character with the same character is possible with an accuracy of ± 0.005 cm, while with machines at higher speeds, for example more than 30 characters per second, such accuracy overprinting cannot be achieved. In type wheel printers, where the types are arranged on flexible spokes that originate from a hub, this problem appears to arise from vibrations in the slim spokes and from the deviations in the hammer alignment, which add to the usual positional deviations of the carriage or the carriage add. Whatever the reasons, it seems that a significant improvement in the overpressure accuracy can only be achieved with great effort and cost, if at all.

In order to avoid the problems mentioned, attempts have been made to completely erase the undesired characters by overprinting them with block types. These block types have special shapes that individually or in groups cover the printing area for any character. However, this solution requires additional types of erasure, which cannot be used for printing purposes, and also leads to problems with the necessary touch strength, which must be very large because of the large contact surface of the special types, which leads to damage to the paper, which affects the appearance of the Affect originals.

Obviously, typewriters that operate at medium to high speeds typically do not have a correction device because of the problems mentioned, and if a correction is required, the unwanted character either has to be erased or covered with a covering liquid by hand, or the whole page is new write.

The present invention does not attempt to

by means of special measures to improve the accuracy of overprinting in impact printers in order to enable the complete eradication of printed characters, rather the present invention enables the complete removal of printed characters with normal alignment accuracy of the types by deliberately deviating from the position of the printed character in in a very specific way. It has been shown that, with normal alignment accuracy, the complete erasure of a printed character is possible if this character is overprinted with the same type with a small lateral shift on both sides in the direction of the step switching.

This is probably due to the fact that with such a positioning the pressure distribution through the type element is generally impressed within the 5

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635030

The contour of the printed character remains, while the zone in which an erasure takes place lies along the axis on which the positioning inaccuracy is concentrated, namely the indexing axis. With this procedure, the displacements on both sides of the printed character are preferably a fraction of a switching step. A shift in the order of 2 to 20% of a switching step has proven to be suitable in order to achieve complete eradication of the sign. Such an area is also sufficient for the various standard fonts used in machines with interchangeable type elements.

In a preferred embodiment of a typewriter which has a step switch detector and which uses a count of the switch steps or a switch step code to control the position of the carriage or slide on which the type element is arranged, the resolution is Step scanning a fraction (»/," or V12) of the character step switching, so that this resolution of the step switching mechanism can advantageously be used for the eradication of undesired characters. In this way, step switching code words are generated. which represent positions which deviate from the position of the undesired character by a fraction of an average character switching step, so that the carriage or carriage can be set to these positions by overprinting on the positions by means of the step switching mechanism which is in any case present. The other functions, such as the stop of the type element and the lifting of the correction tape, are preferably initiated automatically as part of the deletion operation, which is explained further below. In a memory typewriter, the character is preferably selected automatically by means of a code word stored in the memory which corresponds to the nominal deletion position.

An alternative embodiment of the present invention is conceivable by setting the type carrier to the position of the undesired character (with normal accuracy), in which case the lateral displacements are brought about by a separately controllable displacement mechanism which is arranged on the carriage and which is used for the deletion after the present invention superimposed switching step increments. It is already clear from the above that either the type element or the paper carrier, or both, can be arranged so as to be displaceable along the printing line in order to produce the relative displacement between the two for the positioning.

For the application of the invention in a high-speed printer, such as a spoked wheel printer, it is proposed that the print hammer be equipped with a double electromagnet in order to enable a very rapid second stop for the erasing operation.

Details of embodiments of the invention are described below with reference to the accompanying drawings. The drawings show:

Fig. 1 + 2 cross sections through paper and type element parallel to the step switching direction,

3 shows the essential parts of a carriage drive for a typewriter,

4 is a side view of the ribbon lift mechanism;

5 is a block diagram of an embodiment of the invention,

5 is a block diagram of a character selection device for a print wheel printer.

7 is a block diagram of a preferred embodiment of the invention,

8 shows a flowchart for a preferred sequence of operations for deleting characters,

9 is a side view of a print hammer unit with two magnets,

10 is a front view of a displacement device according to the invention.

1 shows a printing type 1 which is in the process of carrying out an erase stop on the paper 2 in accordance with the present invention. Between the printing type 1 and the io paper 2, an erasing tape 3 has been introduced, which serves to lift the print, hereinafter referred to as color 4, from the paper. According to the invention, print type 1 is identical to the print type used for the unintentional reprint. Print type 1 is shifted laterally by a distance Ai to a first delete position PE1 for the delete-15 process from the original print position. Thereupon the printing type 1 stops and its displacement to a second erasing position PE2 at a distance, A, 2 to the other side of the original printing position Pp. 20 printed character can be achieved without requiring any special accuracy for the erasure print 25. It is also important that no excessive stroke strength is required, so that no damage to the paper can occur, at least not with the typewriter papers that are usually used.

In the following the results of two experiments are shared with -30, in which the present invention was applied in wheel printers. In these experiments, the alignment accuracy for the extinguishing process was checked with a micrometer screw.

35 Test No. 1 normal stroke:

Font: Prestige Elite Power level: 14.4 kg Ribbon: IBM Correctable Film Ribbon Erase tape: IBM Lift-off Tape 40 letters: Y and M.

Minimum displacement: ± 0.05 mm Maximum displacement for complete deletion:

Paper shift (Aj, A2)

Patapar dz 0.4

mm

Cranes dz 0.3

mm

Piover dz 0.3

mm

Weston Opaque dz 0.275

mm

Lancaster Bond dz 0.25

mm

Test No. 2 strong attack:

55 Font: Diablo Manifold Power level: 24.5 kg

Ribbon: IBM Correctable Film Ribbon Erase Ribbon: IBM Lift-off Tape Letters: Y and M 60 Minimum displacement: ± 0.05 mm

Maximum shift for complete deletion:

paper

shift

Cranes crest dz 0.25 mm

Piover dz 0.25 mm

Patapar dz 0.25 mm

63503 »

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Based on these results, it can be determined that shifts in the order of 2 to 20% of the average step switching, which is typically between 2 and 2.5 mm, or 4 to 40% of a character width, which corresponds to about half a switching step, are sufficient for Deletions on different types of paper and the most difficult to delete letters, namely Y and M. Two deletion strokes with the usual setting accuracy of the print type, but without lateral displacement, do not reliably result in complete deletion.

FIG. 3 shows a preferred printing unit in which the present invention can be used and which has a paper carrier, namely a roller 5 and guide rollers 6 cooperating with it. The type element 8, which in the present case is designed as a spoke wheel, is arranged on a carriage 7. The carriage is adjusted along the stepping axis formed by a pair of guide rods 9 parallel to the paper roll by means of a cable 10 which is driven by a motor 11, as is generally known. A converter 12 seated on the shaft of the motor 11 supplies signals SE which are proportional to the number of switching steps. The angular resolution of the transducer 12 is preferably selected so that it delivers approximately 48 pulses per cm of carriage displacement.

In order to print a sign at the printing position Pp along the indexing axis, a selected type 13 is aligned on the type element 8 by a motor 14 with a printing hammer 15. The rotation of the type element 8 takes place under the control of position signals S ,,., Which are supplied by a position converter 16, which will be described below.

The imprint of a character is represented by a. Signal SH causes which is supplied to an electromagnet 17, the armature 18 swivels and drives the hammer 15 against the selected type 13 of the type element 8.

Ribbon lifters 19 and 20 serve to lift the ribbon 21 and the erasing tape 3. The ribbon lifter 19 is pivoted by an electromagnet 22, which is controlled by a signal SR, and the lifter 20 is pivoted by an electromagnet 23, which is controlled by a signal ST becomes.

4, the ribbon lifting mechanism 24 for the adjustment of the ribbon 21, which emerges from a cassette 25, between the roller 5 and the type 13, the ribbon lifter 19, which is arranged in operative connection with the electromagnet 22. The ribbon lifter 19 drives a lifting linkage 26 with which the ribbon 21 is adjusted. The extinguishing belt lifting mechanism 27 for setting the extinguishing belt 3 between the roller 5 and the type 13 comprises the ribbon lifter 20, which is arranged in operative connection with the electromagnet 23. The ribbon lifter 20 is connected to a linkage 28,

over which the extinguishing tape 3 runs. 5 shows a basic circuit diagram of a signal processing device which supplies the signals required for driving the typewriter described. The signals required for character selection or deletion are supplied to a processor 30 as input data from a manually operated keyboard 29. The processor 30 stores an erase bit in a register 31. Step code words which represent the current step position of the carriage 7 are stored in a step register 32, and the code words for the position of the type element 8 are stored together with a direction bit ( CW) stored in a register 33. For the sake of completeness, a register 34 for the line connection is also shown in FIG. 5,

but that is not discussed further. The demultiplexing of the information arriving via an input circuit is coordinated by a decoder 36 which is connected to the control line 37 of the processor 30.

A sequence control circuit 38 uses a signal “load” to initiate data transmission to a buffer memory 39, a line counter 40, a switching step counter 41 and a selection counter 42.

According to FIG. 6, the circuit responsible for the selection of the types comprises a logic control circuit 43, the output signals SCW and SCCW of which cause the motor 14 to run in one direction or the other, depending on the status of the signal CW from the selection counter. A selection is initiated on the basis of a signal SSTART when a code word which is not equal to zero is entered into the selection counter 42. A decoder 44 generates a logic signal SÈL0 to indicate when the total of the shift As in counter 42 is reduced to zero, i.e. when the selection is complete.

The pulses required for counting down the counter 42 are supplied by the logic control circuit 43 on the basis of the signal Sw from the converter 16. The signal As denotes the distance from the predetermined target and can be used by the logic control circuit 43 for controlling the speed of the motor 14.

The control circuit 45 (FIG. 7) responds to the SEL0 signal, which, as mentioned, indicates the end of the selection, and to the delete signal from the processor 30 due to the operator actuating the keyboard 29 to determine the position of the ink ribbon 21 (FIG. 4) by means of the input signal SR of the ribbon mechanism 24.

The switching steps required for the implementation of the invention are preferably carried out by the existing step switching device. An erase control circuit 46 triggers the step control circuit 47 by sending special erase signals via the logic circuits 48, 49 and 50, and by introducing displacement values by means of an encoder 51. The signal STARTE emitted by the erase control circuit 46 guides the erase process on, the signal LO ADE is a special command for the counter 41, the signal REVE indicates the step direction during the erase operation, and the signal E'CNTE causes the counter 41 to count up. Correspondingly, but without the suffix E, the signals required for the normal write operation are designated.

The erase control circuit 46 works sequentially and can be designed, for example, as a microprocessor, like the processor 30. A description of the control circuit 46 is given in connection with the comparison and command structure shown in FIG.

An erase operation begins with the "erase" command on the buffer memory 39 and a selection code word on the selection counter 42 (FIG. 5). When the circuit of FIG. 6 has completed a character selection operation, the SEL0 signal is set to 1 and the gate circuit 52 then outputs a signal which corresponds to a logic 1. According to FIG. 8, the control circuit 46 checks in block 53 whether the delete signal from the gate circuit 52 is 1, whereupon the signal “LOADE” is set to 1 in block 54, as a result of which the step value in register 32 is transferred to the switch step counter 41 (see Fig. 7).

A count pulse ECNTE is then applied to logic circuit 48 (block 55 in Fig. 8) which causes counter 41 to count down. In block 56, the signal REVE is set to 1 and transmitted to the stepping control circuit 47 via the gate circuit 57 (FIG. 7). This command brings the stepping circuit to a position that wel5

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one step beyond the position of the character to be deleted. The step switching is triggered by the signal STARTE being set to 1 (block 58). The signal STARTE passes the logic circuit 50, to which the normal signal START is also present, and reaches the AND gate 59. This gives an output signal to the step switching control circuit 47 if the decoder 60 indicates that the total shift A in the counter 41 is not 0, ie the complement of the signal indicating that the target has been reached (ESC0) is a logical 1.

The direction of the stepping caused by the motor 11 can be forward or backward, depending on the presence of one of the signals DFWD and DREV. The rotation of the motor 11 is transmitted to the cable 10 and to the converter 12, which generates the feedback signal SB. The signal SE passes through a square element 61, the output signal ECNT of which decrements the counter 41. As soon as the goal of stepping is reached, the signal ESC0 is set to 1, which satisfies the test in block 62 of FIG. 8.

The step switching target mentioned is a switching step from the position of the undesired character and, according to the present invention, represents the first deletion position. In block 53, the STARTE signal is set to 0 and the ST signal, which causes the deletion tape to be lifted, to 1 (block 64 ). After a delay in the delay element 65, which corresponds to the operation time of the extinguishing belt lifting mechanism 27, the signal ST indicates that the extinguishing tape is in the working position (block 66). The signal ST also passes through a gate circuit 67 and reaches the input of a hammer control unit 68. With the aforementioned setting of the signals ESC0, RR, SEL0 and the signal IHE equal to 0, the hammer control unit 68 supplies a hammer pulse SH to the electromagnet 17, who operates the hammer 15. The pulse SH also goes to a monostable circuit 69, which emits a signal H 'after a delay corresponding to the working cycle of the hammer 15, to an ink ribbon and erase ribbon transport device 70, and to the erase control circuit 46 (block 71 Fig. 8 ).

A "flying" deletion can be initiated in that the hammer pulse SH is triggered by a signal ESCI which indicates that the carriage 7 is one switching step in front of the target.

After executing the first delete stop, the switching step counter 41 is incremented by the encoder 51 by two steps (block 72), so that the new counter content corresponds to the second delete position. The REVE signal remains 1 (block 73) and the STARTE signal is set 1 (block 74), whereupon a stepping operation similar to that described above can begin and continue until the ESC0 signal becomes 1 (block 75). Under these conditions, hammer control unit 58 sends out a hammer pulse SH and erase control circuit 46 waits for signal H 'to go to zero (block 76, Fig. 8). When the second erase stop has occurred, the erase band is lowered by the signal ST becoming 0 (block 77).

«35030

In order to return to the position of the character to be deleted, the signal STARTE is set to 0 (block 78) and the switching step counter 41 is incremented by one step via the encoder 51 (block 79). The REVE signal becomes 0 (block 80) and initiates a switching step in the forward direction. The hammer lock signal IHE is set equal to 1 (block 81). Then the stepping operation begins by setting the START signal equal to 1 (block 82). Under these circumstances, the switching takes place until the position of the deleted character (Pp) is reached, whereupon the signal ESC $ is set to 1 by means of the decoder 60 (block 83 in FIG. 8). At the end of the order sequence for the delete control circuit 46, the STARTE signal is set to 0 (block 84).

FIG. 9 shows a special embodiment of the pressure hammer mechanism 85, which is designed for high-speed erasing and two electromagnets 17 and

86 to allow rapid repetition of the hammer operation in the delete operations. When the hammer is operated a second time, as described in connection with FIG. 8, in this exemplary embodiment the electromagnet 86 would be controlled by the signal S'H in order to avoid the delay between successive actuations of the electromagnet caused by the circuit inductance. By means of the attacks

87 and 88, the stroke of the armature 18 is limited.

As an alternative to the described possibilities for setting the erasing position according to the present invention, the device according to FIG. 10 can bring about lateral displacements from the printing position independently of the normal step switching device of the carriage 7. On the frame 89 of the carriage 7, a mounting bracket 90 is arranged, which can carry out a lateral displacement parallel to the axis of the stepping circuit, in that guide pins 91 are mounted in elongated holes. A motor 92 generates precisely dimensioned displacements of the bracket 90 in the stepping direction by rotating an eccentric 93, which is in operative connection with the surfaces 94 and 95 of the mounting bracket 90. The excitation of the hammer magnet for quenching is coordinated in time with the reaching of the maximum displacement of the bracket 90 given by the eccentric 93.

Although the invention has been described with reference to exemplary embodiments shown in the drawings, it is obvious that various variants and changes are possible without departing from the inventive concept. For example, both a sticky lifting tape and a masking tape can be used to erase the unwanted character, and one can use the carriage drive normally present in the machine or an independent displacement mechanism. Furthermore, the type element can be designed as a type basket, ball head or type wheel for an impact printer. In a typewriter with memory for code words which represent characters to be printed on a line, the middle] for the type selection for deletion can consist in a lookup logic which searches for the code word assigned to the deletion position.

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6 sheets of drawings

Claims (6)

635030 1. A method for erasing undesired characters in impact prints which have at least one type element and a paper carrier and a step-switching device for producing a relative displacement between the type element and paper carrier, characterized by the following steps: generating an erase signal which indicates the position of the character to be erased, Selecting and setting the type (13) intended for performing the delete operation in the printing position, Moving the type element (8) by a fraction of a switching step to one side of the position of the character to be deleted, Setting a correction means (3) from its rest position into its working position between the type element (8) and the paper carrier (5) and printing the selected type (13), Moving the type element (8) by a fraction of a switching step to the other side of the position of the character to be deleted and reprinting the selected type (13), returning the correction means (3) to its rest position. 2. The method according to claim 1, characterized in that the lateral displacement of the type element (8) is between 2 and 20% of a switching step. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the lateral displacement of the type element (8) by a fraction of a switching step is between 4 and 40% of a type width. 4. Apparatus for carrying out the method according to claim 1, with at least one type element, a paper support and a stepping device for the relative displacement between the type element and paper support along the printing line, with means for generating an erase signal which corresponds to the position of the character to be deleted, and with means for selecting a type of the type element for eradication, characterized by a shifting device (90 ... 95) which can be controlled by the deletion signal and which interacts with the stepping device, and which can be adjusted from a rest position into two working positions for shifting the printing position of the deleting type on both sides ( 13) from the printing position of the character to be erased, and by means of a hammer unit (85) interacting with the type element (8) and the displacement device (90 ... 95) with a hammer (15) and two magnets (17, 86). 5. The device according to claim 4, characterized in that the displacement device has a bracket (90) which is slidably mounted with pins (91) in elongated holes in a frame (89) in the step-switching direction, and which carries the type element (8), which Bracket (90) has surfaces (94, 95), between which an eccentric (93) which can be driven by a motor (92) and which bears against the surfaces (94, 95) is rotatably arranged. 6. The device according to claim 4, characterized in that the hammer unit (85) has a longitudinally displaceably mounted hammer (15), one end of which cooperates with a pivotably mounted armature (18), which armature (18) in operative connection with a first electromagnet ( 17) and in operative connection with a second electromagnet (86) (and the other end of which is aligned in the printing position.