CH668745A5 - METHOD FOR DELETING ERRORLY PRINTED LETTERS IN WRITING OR SIMILAR OFFICE MACHINES. - Google Patents

Description

DESCRIPTION

The object of the invention is a method for deleting erroneously printed characters in typewriters or similar office machines according to the preamble of patent claim 1.

Typewriters and similar office machines usually have printing devices which are arranged on a carriage which can be moved along the printing line. The carriage is preferably driven by a stepper motor which, fixed in the frame in the housing, moves the carriage along the writing line via a toothed belt or a cable. The carriage is located next to the printing element, which is usually a so-called sum type carrier, a positioning device for the printing element, a knock-off mechanism, an ink ribbon, a correction tape and a mechanism for lifting and transporting the inking or the correction tape. In such typewriters, erroneously printed characters are erased by adjusting the carriage to the position of the character to be erased and the printing element itself to the character to be erased, and by printing the character again with the correction tape instead of the ink ribbon. If the correction tape is a tape with a sticky coating, the letter is lifted off the paper during this process. If, on the other hand, the correction tape is provided with a color layer similar to the color of the paper, the letter is overprinted.

In the practical application of this correction method, the problem now arises that even a slight offset in the carriage position in the erasure print compared to the carriage position in the printing of the character leads to color residues remaining at the edge of the character or not being covered.

Since 55 reproducible positioning accuracies of + Vioo mm, which would be necessary for a satisfactory correction, cannot be achieved with slide drive systems of the type mentioned above, various attempts have been made to remedy this problem. For example, US-PS 43 07 971 describes a correction method which provides for a carriage driven by means of a servo motor to be displaced by one basic step from the exact position of the character to be deleted in or against the writing direction in order to delete one operation at a time perform in these positions. When attempting to apply this method to systems in which the carriage is driven 65 by a stepper motor, it must be found, however, that the minimum possible step size of Vuo inches which is customary in such systems is not sufficient to achieve a satisfactory deletion of such characters as well that have a very small line width, especially for characters with

Slash components such as B. M, W, X, Y, / etc., have. The use of higher-resolution stepper motors or a reduction gear is forbidden for cost reasons or because of the decrease in the positioning speed.

Another method for controlling the correction process is known from DE-AS 28 31488. There it is proposed to carry out a pilgrim step movement with the carriage before each deletion process, so that the carriage always approaches the correction position in the writing direction. This ensures that the gearless are pulled out in the writing direction, which leads to a more precise positioning. This method also does not completely remedy the defect shown at the beginning.

A combination of the two methods mentioned above can be found in DE-OS 28 29 078. This method also does not allow a satisfactory result for typewriters with a minimum step size of the slide of V120 inches, since a lateral offset of the erasure impressions by '/ 120 inches, i.e. by approx. 0.2 mm, is too large, even for characters with cross-stroke components and low stroke width to achieve complete deletion, even if more than two deletions are made. In order to achieve a smaller distance than the one given by the minimum step size of the carriage between the position of the character to be corrected and the erasure marks shifted in or against the writing direction, EP-OS 38 456 proposes to carry out the positioning in this way that the filing from the exact position of the character to be deleted is achieved by deliberately exploiting the gearless. Since the construction of a typewriter for normal typing is designed to minimize the play of the gears in favor of an exact text, the gears are very small and, moreover, cannot be reproduced exactly, so that this method also has a considerable defect.

It is therefore an object of the invention to provide a method which makes it possible to completely erase an erroneously printed character while avoiding the above-mentioned disadvantages of already known methods. In particular, it is the task of specifying a method with which it is possible, with sufficiently exact reproducibility, to produce deletion imprints which are closer than the minimum increment of the carriage to the position of the character to be deleted.

The object is achieved by the characterizing features of patent claim 1. Further design options of the method according to the invention are characterized in the dependent patent claims.

In the method according to the characterizing part of patent claim 1, there is a simple way to achieve complete deletion of an erroneously printed character, even in typewriters whose slides have a relatively large step size, by at least two printing processes with the correction tape in the working position.

In patent claims 2 to 5, some advantageous embodiments of the extinguishing method are characterized. A combination of pilgrim movements of the sled and only two erasure prints completely erases the mistakenly printed character.

The characterizing part of patent claim 6 shows how the fact that the step-by-step slide motors operated in half-step operation, depending on whether a step leads into a full step position or into a half step position, has a different torque in the deletion method according to the invention.

A more detailed description of the method according to the invention and of some design examples is given below using the figures. Show it:

1 is a block diagram of a typewriter;

2a to 2d are schematic representations of different variants of a deletion process with two deletion discounts;

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Fig. 3 is a schematic representation of an extinguishing process with three extinguishing discounts.

To explain the method according to the invention, an electronic typewriter as shown in a block diagram in FIG. 1 is assumed. According to the prior art, such a typewriter has a programmable control unit 1, which usually consists of a microprocessor 2, a ROM memory 3 which contains the control programs and a RAM memory 4 which contains the variable data,

consists. This programmable control unit 1 is connected via lines and optionally via control circuits (not shown) to a keyboard 5, a type wheel motor 6, a knock-off mechanism 7, a sled motor 8, a ribbon mechanism 9, a paper transport motor 10 and, if appropriate, to further devices (not shown). Since such typewriters are generally known, a detailed description of the individual components is unnecessary. It should only be pointed out that the carriage motor 8 is a stepper motor operated in half-step mode, that is to say with the greatest possible angular resolution, which is preferably arranged fixed to the frame and is connected via traction means, e.g. B. timing belt or cable, acts on the sled.

The carriage itself carries the type wheel motor 6 with the type wheel (not shown), the knock-off mechanism 7 and the ribbon mechanism 9. The ribbon mechanism 9 is to be understood as the drive and the mechanical gears for lifting and transporting the ribbon or the correction ribbon as a whole.

In typewriters of the type mentioned above, the erroneous printing of a character is carried out by first setting the carriage to the position of the character to be deleted by actuating corresponding positioning keys on the keyboard 5, the carriage motor 8, controlled by the programmable control unit 1. Then the actual deletion process is triggered by pressing a correction key. The erasing process itself is composed of a series of control steps which are stored in the ROM 3 and by the microprocessor

2 processed automatically after the deletion process has been triggered.

As already mentioned above, for a complete deletion it is not sufficient to carry out only one printing operation with the type carrying the character to be deleted with the correction tape in the working position. It has therefore already been proposed to carry out a plurality of such printing processes, the carriage moving between the printing processes so that the prints produced in this way partially overlap. If the sled motor is now a stepper motor operated in half-step, i.e. with maximum angular resolution, the smallest step size of the sled in today's typewriters is Vizo inches. The smallest possible reproducible offset of the carriage with respect to the position of the character to be corrected is therefore also Vi 20 inches, that is about 0.21 mm. However, this offset is too large to achieve a complete deletion even with characters with a small stroke width, especially if these characters have slash components. Tests have shown that the best results are achieved with a carriage offset of approx. 0.1 mm, based on the position of the character to be deleted. For the complete deletion of a character, a method is therefore proposed in which at least one of the printing operations is carried out so that the type carrying the character to be erased hits the paper during the movement phase of the carriage with the correction tape in the working position, specifically such that the print thus produced is less than the minimum increment of the carriage from the exact position of the character to be deleted.

As already mentioned above, the erasing process is composed of a large number of control steps which are stored in the ROM memory

3 of the typewriter are stored and by the microprocessor 2

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be executed automatically after the deletion process is triggered. In these control steps, it is determined, among other things, at what time during the deletion process the programmable control unit 1 triggers the printing processes by actuating the knock-off mechanism 7. Since on the one hand the temporal movement behavior of the carriage motor 8 or of the carriage during a step sequence with a predetermined number of steps and a predefined direction of movement and on the other hand the temporal movement behavior of the knock-off mechanism 7 can be determined very precisely by measurements, it is possible to trigger at least one of the printing processes in this way, that the type carrying the character to be deleted hits the paper with the correction tape in the working position at a time at which the carriage has traveled a predetermined distance. The triggering time is of course dependent on the construction of the typewriter, so that no generally valid numerical value can be given. However, it was found that a triggering time determined by measurement on a typewriter of a certain type can be transferred to a production series with very good reproducibility. The above-mentioned method thus makes it possible to generate erasure prints with the correction tape in the working position, which are a very specific distance from the position of the character to be erased, which distance can be smaller than the minimum increment of the carriage.

How such prints can be integrated into the entire deletion process is explained below in connection with the block diagram according to FIG. 1 with reference to FIGS. 2a to 2d and FIG. 3. It is assumed that the carriage is in the position of the character to be deleted and that a deletion process has been triggered by pressing the correction key.

By triggering the deletion process, the programmable control unit 1, by appropriately actuating the type wheel motor 6, adjusts the type wheel so that the type carrying the character to be deleted is in the printing position, and brings the correction tape into the working position by actuating the ribbon mechanism 9 accordingly.

As shown in Fig. 2a, the programmable control unit 1 now generates a first step sequence 12 by appropriately controlling the carriage motor 8, which consists of four steps in the opposite direction to the writing direction 11 and four steps in the writing direction 11, so that the carriage after execution of the eight steps is again at position 15 of the character to be deleted. In this way, a relatively precise positioning on the character to be deleted is achieved by pulling out the gearless in the writing direction. When the pouring is stopped, triggering the tee mechanism 7 results in a first erase AI, which already deletes most of the character. After this discount, the programmable control unit 1 brings fresh correction tape into the imprint area by appropriately controlling the ink ribbon mechanism 9 and triggers a second step sequence 13, which consists of two steps in the writing direction, by actuating the carriage motor 8. At a predetermined time t stored in the ROM memory 3 after the triggering of the first step of the second step sequence 13, the programmable control unit 1 controls the tapping mechanism 7, so that during the execution of the first step of the second step sequence 13 after the slide approx. 0.1 mm, there is a second A2 cancellation. This second deletion mark completely deletes the color residues that remained after the first deletion mark. After execution of the second step sequence 13, the programmable control unit 1 controls the carriage motor 8 such that the carriage executes a third step sequence 14, which consists of four steps in the opposite direction to the writing direction 11 and two steps in the writing direction 11. After execution of this third sequence of steps 14, the carriage is again relatively exactly in position 15, and the printing of the correct character can be triggered by pressing the corresponding key on keyboard 5.

A modification of the method according to FIG. 2a is shown in FIG. 2b. As far as the carriage movement is concerned, the control steps of these two methods do not differ, so that only those control steps which relate to the deletion discounts are explained in more detail with reference to FIG. 2b.

As can be clearly seen in FIG. 2 b, the first deletion cut-off AI already takes place during the last step of the first step sequence 12. For this purpose, the programmable control unit 1, after having triggered the last step of the first step sequence 12 by correspondingly actuating the slide motor 8, after elapse a time tl, which is stored in the ROM memory 3, the striking mechanism 7 so that the type carrying the character to be erased hits the paper with the carriage moved before reaching the position of the character to be erased with the correction tape in the working position. After completion of the first step sequence 12, the programmable control unit 1 brings fresh correction tape into the printing area by appropriately controlling the ribbon mechanism 9 and triggers the second step sequence 13. At a predetermined time t2 stored in the ROM memory 3 after the triggering of the first step of the second step sequence 13, the programmable control unit 1 controls the discount mechanism 7, so that a second delete discount A2 takes place during the execution of the first step of the second step sequence 13.

The deletion discounts AI and A2 should be slightly closer than 0.1 mm to the exact position of the character to be deleted in this procedure, which must be taken into account when determining the times t1 and t2.

2c shows a further modification of the method according to FIG. 2a. In this method too, the movement of the carriage corresponds to the carriage movement according to FIG. 2a, so that the repeated description of the control steps in this regard is unnecessary.

The first erase markdown AI takes place during the last step of the first step sequence 12. After the triggering of the last step of the first step sequence 12, the programmable control unit 1 controls the markdown mechanism 7 after the lapse of a time t3, which is stored in the ROM memory, so that the type carrying the character to be deleted hits the paper before the position of the character to be deleted is reached with the correction tape in the working position. After completion of the first step sequence 12, the programmable control unit 1 brings fresh correction tape into the printing area by appropriately controlling the ink ribbon mechanism 9 and triggers a second erasing discount A2 by actuating the discount mechanism 7, so that the type carrying the character to be deleted with the carriage stationary and in Correction tape located on the working position hits the paper. The time t3 must also be determined empirically in this method.

Of course, with the method according to FIGS. 2a to 2c, there is the possibility of reversing the direction of the carriage movement. This will be shown below with reference to FIG. 2d. As shown there, the programmable control unit 1 first generates a first step sequence 16 by appropriately controlling the carriage motor 8, which comprises four steps in the writing direction 11 and four steps in the opposite direction to the writing direction 11. After the programmable control unit 1 has triggered the last step of the first step sequence 16, it triggers the tee-off mechanism 7 after a time t4 has passed, so that even before the end of the first step sequence 16 with a correction band in the working position and with a moving slide, a first deletion tee AI is included the type carrying the character to be deleted. After completion of the first step sequence 16, the programmable control unit 1 brings fresh correction tape into the printing area by appropriately controlling the ribbon mechanism 9 and triggers a second step sequence 17 by controlling the carriage motor 8, which comprises two steps in the opposite direction to the writing direction 11 and two steps in the writing direction 11 consists. After triggering the first step of the second step e5

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quenz 17 controls the programmable control unit 1 after a time t5, which is stored in the ROM memory, the tee mechanism 7, so that when the slide is in motion and when the correction tape is in the working position, a second erase tee A2 occurs between the position of the item to be deleted Character and the position that the carriage takes after performing the first step of the second step sequence 17. After completion of the second step sequence 17, the carriage is relatively exactly in the position desired for the subsequent printing of the correct character, since the second step sequence 17 eliminates the gearless in the writing direction.

In extinguishing methods, such as that described above, in which the direction of movement of the carriage is reversed compared to the extinguishing methods as described for FIGS. 2a to 2c, the gearlessness is not eliminated before the deletion discounts are carried out. This fact must be taken into account when choosing times t4 and t5 at which the deletion discounts should be triggered when the carriage is moving.

As a last example, a deletion method in which three deletion discounts are carried out is described below with reference to FIG. 3. In this example, the carriage movement corresponds to the carriage movement as described for FIG. 2d, so that the description of the associated control steps is unnecessary. Therefore, only the actual deletion of the sign is discussed.

After the programmable control unit 1 has triggered the last step of the first step sequence 16, it triggers the tee-off mechanism 7 after a time t6 has elapsed, so that even before the end of the first step sequence 16 with a correction band in the working position and with a moving carriage, a first deletion tee AI is included the type carrying the character to be deleted. After completion of the first step sequence 16, the programmable control unit 1 brings fresh correction tape into the printing area by appropriately controlling the ink ribbon mechanism 9 and triggers a second erase discount A2 by actuating the discount mechanism 7 when the slide is stationary and the correction tape is in the working position. After the tapping has been carried out, the ribbon mechanism 7, controlled by the programmable control unit 1, conveys fresh correction tape into the printing area. After triggering the first step of the second step sequence 17, the programmable control unit 1 controls the tee-off mechanism 7 after a time t7 that is stored in the ROM memory 3, so that a third erase tee A3 occurs when the slide is moved and the correction tape is in the working position which lies between the position of the character to be deleted and the position which the carriage takes after the first step of the second step sequence 17 has been carried out.

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As for FIGS. 2a to 2d and for FIG. 3, deletion methods all provide one or more deletion discounts when the carriage is in motion. For this purpose, as explained above, it is necessary to trigger the respective deletion discount by actuating the discount mechanism a certain time (t to t7) after triggering a specific step of the slide motor 8. Since the carriage motor 8, as already mentioned, is operated in half-step operation, different torques act on the rotor of the carriage motor, depending on whether the step just carried out leads to a full step position (large torque) or to a half step position (small torque). This has a very strong effect on the temporal movement behavior of the sign. It is therefore necessary to provide two values for the times stored in the ROM memory 3 (t to t7), as are used in the above examples to simplify the illustration, which can alternatively be accessed. How this happens is shown below using a specific example.

Before executing a step during which a deletion imprint is to take place, the microprocessor 2 uses a so-called current pattern table contained in the ROM memory 3, with the aid of which it processes step sequences, to determine whether the rotor of the slide motor 8 is in a full step position or in a half step position. If the rotor of the carriage motor 8 is in a full step position, the microprocessor 2 addresses the ROM 3 with a first address and receives a first time value t. If, on the other hand, the position of the rotor of the carriage motor 8 is a half step position, the microprocessor 2 addresses the ROM 3 with a second address and receives a second time value t '. Based on the example shown in FIG. 2a, applied to a specific typewriter, the first time value t corresponds to a time of 3 ms and the second time value t 'corresponds to a time of 1.5 ms. In other words, in these deletion methods the triggering mechanism 7 is activated 3 ms after triggering the first step of the second step sequence 13 if this step leads to a half-step position, and 1.5 ms after triggering the first step of the second step sequence 13 if this step leads to a full step position.

Regarding the deletion method shown in FIGS. 2a to 2c, it should also be noted that it may be necessary that the sequence of steps 13 must be extended by a few steps in the writing direction 11 in order to ensure that the correction tape possibly adhered to the correction point is torn off safely . Of course, this subsequently extends the subsequent step sequence 14 accordingly.

The same applies with regard to the step sequence 17 with regard to the examples according to FIGS. 2d and 3.

As already stated, the design of the deletion process depends on the construction of the typewriter in which it is to be used, so that the deletion process described is only of exemplary character.

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Claims (6)

668 745 1. A method for deleting an erroneously printed character in typewriters or similar office machines which have a carriage which can be moved step by step along the writing line by means of a stepper motor controlled by a programmable control unit, the deletion of the erroneously printed character being controlled by the programmable control unit , so that with a correction tape arranged between the impression parts and a sum type carrier, at least two printing processes are carried out with the type carrying the character to be deleted, a movement of the carriage taking place between the printing processes so that the prints partially overlap, characterized in that at least one of the printing operations is carried out so that the type carrying the character to be deleted hits the paper with the correction tape in the working position during the movement phase of the carriage, in such a way that the generated impression is less than the minimum increment of the carriage from the position of the character to be deleted. 2. The method according to claim 1, characterized in that during a deletion process a) the programmable control unit controls the stepper motor so that the carriage executes a first step sequence consisting of a first number of steps against the writing direction and the same number of steps in the writing direction ; b) the programmable control unit triggers a first printing operation with the type carrying the character to be deleted when the carriage is stationary; c) the programmable control unit controls the stepper motor after the impression has been taken so that the carriage executes a second step sequence consisting of at least a second number of steps in the writing direction; d) the programmable control unit triggers a second printing process with the type carrying the character to be deleted, such that the type strikes the paper during the first step of the second step sequence. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that during a deletion a) the programmable control unit controls the stepper motor so that the carriage executes a first step sequence consisting of a first number of steps opposite to the writing direction and the same number of steps in the writing direction ; b) the programmable control unit initiates a first printing operation with the type carrying the character to be deleted in such a way that the type strikes the paper during the execution of the last step of the first sequence of steps; c) after the execution of the first step sequence, the programmable control unit controls the step motor in such a way that the carriage executes a second step sequence consisting of at least a second number of steps in the writing direction; d) the programmable control unit triggers a second printing process with the type carrying the character to be deleted, such that the type strikes the paper during the first step of the second step sequence. 4. The method according to claim 1, characterized in that during a deletion a) the programmable control unit controls the stepper motor so that the carriage executes a first step sequence consisting of a first number of steps opposite to the writing direction and the same number of steps in the writing direction ; b) the programmable control unit initiates a first printing operation with the type carrying the character to be deleted in such a way that the type strikes the paper during the execution of the last step of the first sequence of steps; c) the programmable control unit, after executing the first step sequence with the carriage stationary, triggers a second printing operation with the type carrying the character to be deleted; d) the programmable control unit controls the stepper motor after the impression has been taken so that the carriage executes a second step sequence consisting of at least a second number of steps in the writing direction. 5. The method according to claims 2 to 4, characterized in that the programmable control unit controls the stepper motor so that the first step sequence of the carriage is composed of a first number of steps in the writing direction and the same number of steps against the writing direction, io and that the second step sequence consists of at least a second number of steps against the writing direction. 6. The method according to claims 1 to 5, wherein the stepper motor is operated in the half step, characterized in that the programmable control unit determines before the execution of a step, 15 during which a printing process takes place, whether the stepper motor in the execution of the step in a half step position or changes to a full step position, and that the programmable control unit triggers the printing process when changing to a half step position a predetermined time later than 20 when changing to a full step position.