CARRIAGE MOVEMENT CONTROL IN A PRINTER

Abstract: In a printing apparatus wherein the print direction is selected properly on a print line basis so that the path of movement of a carriage (22) becomes shortest, a problem exists that intervals between characters are not kept constant due to backlash or elongation of a wire of a carriage driving system when the print direction is reversed. The disclosed is a printing apparatus which performs regulation of the positional errors of the carriage (22) due to backlash and wire elongation by moving the carriage to the print start position after moving it to the print position preceding the print start position when the print direction of a print line is reverse to the print direction of the succeeding print line (5), and a printing apparatus which performs regulation likewise the above-mentioned in the case where the direction of movement of the carriage (22) to the relocation position is reverse to the print direction of succeeding printing when the original position of the carriage (22) is set again in response to a suspension of printing.

Description: The present invention relates to a printing apparatus capable of printing in both directions on a print line basis, and specifically relates to a printing apparatus wherein when printing a document on a plurality of print lines, intervals between characters on each print line are kept constant, for instance on resumption of printing after printing has been suspended. Generally, some of printing apparatuses such as electronic typewriters and printers are constituted so as to print, when print data sent from an external apparatus is printed on a plurality of print lines, in one direction from the left margin position to the right margin position, and some of printing apparatuses are constituted so as to print in both the right direction and the left direction to improve the printing speed. Some printing apparatuses capable of printing in both directions have been proposed wherein, as described in U.S. Pat. No. 3,764,994, when printing is made on the succeeding print line, the left end print position (line-head print position) and the right end print position (line-end print position) of that line are evaluated by arithmetic operation, and the carriage is moved from the last print position of the preceding line to the closest print start position, which is either the left end print position or the right end print position (i.e. shortest-path control), and thereby the printing speed is improved. For example, as shown in Fig. 9, in the case where printing on a preceding print line (a line segment F) in the right direction is completed, when a last print position Ep thereof is located between a left end print position Lp and a right end print position Rp of a succeeding print line (a line segment S), firstly a print paper is fed by an amount of line space by a line feed processing, and subsequently, the carriage is moved to the right end print position Rp, and the line end character is printed on the right end print position Rp, and thereafter the control is performed so that printing is made on the succeeding print line S while the carriage is moved sequentially in the left direction. In the above-described printing apparatuses capable of printing in both directions, various ingenuities have been made for the control for improving the printing speed including the control for making the path of movement of the carriage shortest. For example, as shown in Fig. 9, in the case where printing on the preceding print line F in the right direction is completed, the carriage is moved from the last print position Ep thereof to the right end print position Rp, and the line end character is printed on the right end print position Rp and thereafter printing on the succeeding print line S is made while the carriage is moved sequentially in the left direction, the line end character is printed in the state that the carriage is driven in the right direction, but characters other than the end character are printed in the state that the carriage is driven in the left direction. In this case, the character interval between the end character and the character succeeding the end character becomes smaller than the character interval between other characters due to elongation of a wire or belt and backlash of gears of the driving means for driving the carriage, and therefore the character intervals are not kept constant on the same print line, and positional deviation of printed characters takes place also between the preceding and succeeding print lines, and thus a problem exists. On the other hand, some other apparatuses have the following configuration as disclosed in Japanese Pat. Provisional Publication No. 58-71185. In the course of printing text data stored in the text memory or print data sent from an external apparatus, printing is suspended according to opening of a cover or operating of a stop key to replace a print ribbon or a typewheel, and work of replacing the print ribbon or the typewheel is performed with the cover opened, and thereafter the cover is closed or a restart key is operated to resume the printing, and then the carriage is moved to the origin setting position to set the original position of the carriage, and thereafter the carriage is moved to the succeeding print position, and the printing is resumed. In the above-described printing apparatuses, in the case where the moving direction of the carriage is reverse to the succeeding print direction when the carriage is returned to the succeeding print position to resume printing after suspension thereof, the moving direction of the carriage is reversed after it has been moved to the succeeding print position, and therefore the interval between the character printed before and the character printed on the succeeding print position is elongated and the following character interval is reduced due to backlash and wire extension of the carriage driving means, and thus a problem exists. EP-A-0068122 discloses a bi-directional printing apparatus in which judging means judge whether or not the print end position of a present printing line is closer to the right or left hand end of the next line to be printed, so that the print head can be directed to proceed to the nearer end to begin printing. However, when the end of the present printing line is between the left and right ends of the next line to be printed, although the print head will be directed to the closer end, when printing begins any backlash in the print head drive mechanism will lead to problems with uneven spacing of the printed characters as discussed above in relation to Fig. 9. EP-A-0140389 discloses an apparatus for reducing positional inaccuracies of printed characters arising from timing of the printing operations, particularly during deceleration and acceleration of the print head at the end of and start of a line. It too is not capable of preventing the above discussed problem with uneven spacing resulting from blacklash. According to the present invention there is provided a printing apparatus comprising: memory means for storing code data of characters to be printed so as to correspond to each print position; printing means having a print head mounted on a carriage; carriage driving means for driving the carriage along a print line for printing on a print paper characters corresponding to the code data stored in the memory means; and printing direction control means for controlling movement of the carriage forward or backward while printing along each print line so that the carriage moves along a shortest path; characterised in that the printing apparatus further comprises: judging means for judging, according to data in the memory means, whether or not the print end position of a present print line is located between a print start position and a print end position of a succeeding print line; and control means for controlling the carriage driving means to move the carriage, when said print end position of the present print line is located between the print start position and the print end position of the succeeding print line, to a preceding print position which precedes the print start position in the print direction of the succeeding print line and subsequently to move the carriage in the print direction to the print start position. In a printing apparatus in accordance with the first aspect of the invention all characters of a print line are printed during movement of the carriage in the same direction, and therefore intervals between printed characters are kept constant without being affected by backlash, wire extension or the like of the carriage driving means, and thus the printed document is more smart. According to a second aspect of the present invention there is provided a printing apparatus comprising: memory means for storing code data of characters to be printed so as to correspond to each print position; printing means having a print head mounted on a carriage; carriage driving means for driving the carriage along a print line for printing on a print paper characters corresponding to the code data stored in the memory means; print direction control means for controlling movement of the carriage forward or backward while printing along each print line so that the carriage moves along a shortest path; and original position setting means for setting an original position of said carriage at one movement limit position; characterised in that the printing apparatus further comprises: print suspending means for controlling the printing means to suspend printing in accordance with a suspension command signal; print resuming means for controlling movement of the carriage, when the print suspending means is released, to a print resuming position at which printing is to be resumed, after setting of the carriage to the original position by the original position setting means; and regulating means for regulating backlash in the carriage driving means before resuming printing, when the direction of movement of the carriage from the movement limit position to the print resuming position is reverse to the print direction in which printing is to be resumed, by moving the carriage from the print resuming position in a direction opposite to that in which printing is to be resumed and then returning it to the print resuming position by moving it in the direction in which printing is to be resumed. When the printing operation is suspended by the print suspending means in the course of printing and then the print suspending means is released to continue the printing again, the original position of the carriage is set by the original position setting means, and thereafter the print resuming means returns the carriage to the succeeding print position. Then, where the moving direction of the carriage when returning to the succeeding print position is reverse to the succeeding print direction, a positional error of the carriage due to backlash and extension of the wire or belt is corrected by the regulating means before resuming the printing. Irregular intervals between printed characters when resuming the printing can be prevented and thereby accurate printing can be performed irrespective of the succeeding print direction. The invention will be better understood from the following description of exemplary embodiments which are illustrated in the drawings in which:- Fig. 1 through Fig. 6(b) relate to a first embodiment, and Fig. 1, Fig. 7 and Fig. 8 relate to a second embodiment. Fig. 1 is a perspective view of an electronic typewriter; Fig. 2 is a block diagram of a controlling system of the electronic typewriter in Fig. 1; Fig. 3(a), Fig. 3(b) and Fig. 3(c) are flow charts of control routine of printing in both directions; Fig. 4(a) through Fig. 4(j) are explanatory views showing relations of relative positions of a preceding print line and a succeeding print line, respectively; Fig. 5 is a modified fragmental flow chart of the control routine of printing in both directions; Fig. 6(a) and Fig. 6(b) are modified fragmental flow charts of the control routine of printing in both directions, respectively; Fig. 7 is a block diagram of a modified controlling system of the electronic typewriter in Fig. 1; Fig. 8 is a flow chart of a control routine of regulating backlash; Fig. 9 is a view in accordance with the prior art equivalent to Fig. 4(b). The First Embodiment (Fig. 1 to Fig. 6(b)) Hereinafter, description is made of a first embodiment of the present invention based on the drawings. This embodiment is of the case where the present invention is applied to an electronic typewriter. As shown in Fig. 1, a keyboard 3 is disposed in the front part of a main frame 2 of an electronic typewriter 1, and a printing mechanism PM is installed behind the keyboard 3 in the main frame 2, and a one-line liquid crystal display 75 for displaying inputted characters and symbols is installed in the rear part of the keyboard 3. On the keyboard 3, character keys 10 including alphabet keys, numeral keys and symbol keys, a print start key 11 for printing text data of a text memory 52, a return key 12 and other various function keys 13, 14 are installed as on normal typewriters. As illustrated in Fig. 1 and Fig. 2, the printing mechanism PM is provided with at least a platen 20 for feeding a print paper 15, a line feed motor 89 for driving it and a line feed drive circuit 89a, a carriage 22 supported by a guide 21 parallel with the platen 20, a carriage drive motor 90 for driving the carriage 22 right and left in a reciprocating fashion and a carriage drive circuit 90a, a typewheel 24 housed in a wheel cassette 23 and a typewheel drive motor 96 for driving it and a typewheel drive circuit 96a, a print ribbon 26 stored in a ribbon cassette 25 and a ribbon drive motor 97 for taking-up it and a ribbon drive circuit 97a, a print hammer for hammering a type element 27 of the typewheel 24 and a hammer solenoid 28 for driving it and a hammer drive circuit 28a, a ribbon change-over mechanism selectively disposing the print ribbon 26 or a correction ribbon 29 at the print position, and this printing mechanism PM is similar to the printing mechanism of normal electronic typewriters. In addition, numeral 4 designates a cover capable of opening and closing which shutters the top opening part of a space wherein the carriage 22 moves. The carriage 22 is driven so as to reciprocate forward and backward along a print line on the print paper 15 by means of a well-known carriage driving means CM disclosed, for example, in U.S. Pat. No. 4,044,882. This carriage driving means CM comprises a carriage drive motor 90 installed near a left-side wall of the frame 2, a driving gear 91 on a motor-shaft of the motor 90, a transmitting gear 92 engaged with the driving gear 91, a driving pulley 93 formed integrally with the gear 92, a driven pulley (not shown) installed near a right-side wall of the frame 2, and a wire 94 which is engaged with two pulleys and fixed to the carriage 22 at both ends. Basically, the electronic typewriter 1 is constituted with the key board 3, the printing mechanism PM, a displaying mechanism D, a controlling apparatus C, and the keyboard 3, the printing mechanism PM and the displaying mechanism D are connected to a main CPU (Central Processing Unit) 30 of the controlling apparatus C through a bus 31 including data bus and address bus. The controlling apparatus C is constituted with the main CPU 30, a ROM (Read Only Memory) 40 and a RAM (Random Access Memory) 50 connected to the CPU 30 through the bus 31. A program memory 41 of the ROM 40 stores a control program for controlling the printing mechanism PM and the displaying mechanism D in correspondence to code data inputted from each character key 10 and each function key 13, 14 on the keyboard 3, a control program for controlling printing in both directions as described later. The RAM 50 is provided with a present position memory 51 for sequentially renewing and storing the present position of a print head 27a of the carriage 22 from the absolute origin in correspondence to the print position, a printed data memory 55 for sequentially storing about 500 characters of data such as characters printed in the typewriter mode in correspondence to the print position, an input buffer 56 for storing data such as characters which are inputted from the keyboard 3 or read from a text memory 52 in the memory mode (display mode), the text memory 52 for storing inputted data as file data, a cursor display position counter 57 for counting the cursor display position in response to a movement of the cursor in correspondence to each display position of the display 75, a cursor position pointer 58 for pointing address of the input buffer 56 corresponding to data of the cursor display position counter 57, a print direction flag 53 which is set when printing is made in the right direction (forward direction) and is reset when printing is made in the left direction (backward direction) in printing text data of the text memory 52, a print buffer 54 for sequentially reading text data of one print line to be printed from the text memory 52 or an external apparatus and storing it when the print start key 11 is operated, a left margin position memory 59 for storing the set left margin position, a pitch memory 60 for storing the set print pitch, and the like. In addition, the text memory 52 stores an EOT (End of Text) code following the last data of text data. The main CPU 30 makes the printing mechanism PM print a character or symbol corresponding to the data inputted from each character key 10 based on the control program, and makes the printed data memory 55 store the printed data in sequence in correspondence to the print position. Furthermore, in the memory mode, the main CPU 30 makes the input buffer 56 store the inputted data of one print line, makes the display 75 display that data, and makes the text memory 52 store that data of one print line in response to an operation of the return key 12. The displaying mechanism D is constituted with an interface 70, a CPU 71 for display, a character generator 72, a display controller 73, and the liquid crystal display 75, and the connection thereof is as shown in the diagram. In addition, the displaying mechanism D is similar to the publicly known mechanism, and does not relate directly to the present invention, and therefore description thereon is omitted. Next, description is made on the control of printing in both directions performed by the controlling apparatus C of the electronic typewriter 1 with reference to the flow chart in Fig. 3(a) through Fig. 3(c) together with Fig. 4 (a) through (j). In Fig. 4 (a) through (j), a line segment F shows a character string printed on a preceding line, and a line segment S shows a character string printed on a succeeding line. Symbol Ep designates the last print position of the preceding print line, symbol Lp designates the left end print position (line-head print position) of the succeeding print line, symbol Rp designates the right end print position (line-end print position) of the succeeding print line, a dotted line shows print paper feed, an arrow "→" shows movement of the carriage 22 in the right direction and an arrow "←" shows movement of the carriage 22 in the left direction. By turning on the power switch of the typewriter 1, this control is started, and processing proceeds to step S1 (hereinafter represented simply by S1, and the same is true of the other steps), and initialization is executed in such a manner that the print direction flag 53 is set to print characters on the preceding line in the right direction (print direction flag data "1") and so on, and in S2, the typewriter 1 is ready for a key-input. When a key-input is given, processing proceeds to S3. In S3, judgment is made on whether or not it is the print start key 11, and if it is the print start key 11, processing proceeds to S4. In S4, text data of the first one print line is read from the text memory 52, being written to the print buffer 54. In the following S5, judgment is made on whether or not text data exists based on data of the text memory 52, and if text data exists, processing proceeds to S6. In addition, after printing, the print head 27a is moved right by one character. At this time, the main CPU 30 outputs a control signal to each drive circuit 89a, 90a, 96a, 28a, 97a, 99a of the printing mechanism PM.In addition, the print head 27a consists of a print hammer, a type element 27 facing this print hammer and the print ribbon 26 facing this type element 27. Next, in S7, data to be printed next is read from the print buffer 54. In S8, judgment is made on whether or not that data is end data (EOT code), and if it is not the EOT code, processing proceeds to S9. In S9, judgment is made on whether or not that data is the last data of line, that is, data preceding by one character before return code, and if NO, processing returns to S6. Then, S6 - S9 are repeated, and for example, when printing is made up to data preceding by one character before the last print position Ep of the line segment F as shown in Fig. 4 (a) through (j), judgment is made to be YES, and processing proceeds to S10. In S10, the last data of print line is printed on the last print position Ep. In addition, at this time, the print head 27a is located at the last print position Ep. In S11, text data of the following one print line is read from the text memory 52, being written to the print buffer 54. In S12, according to data of the present position memory 51, data of the print buffer 54 and data of the pitch memory 60, the left end print position Lp and the right end print position Rp of the line segment S in the succeeding print line are evaluated by arithmetic operation, and judgment is made on whether or not the last print position Ep is located between the left end print position Lp and the right end print position Rp, and if the judgment is YES, positional errors due to backlash and wire elongation of the driving means driving the carriage 22 is required to be regulated, and therefore processing proceeds to S13. For example, as shown in Fig. 4 (b) and (e), the last print position Ep is located between the left end print position Lp and the right end print position Rp of the line segment S. In S13, judgment is made on whether or not the absolute value of the last print position Ep minus the left end print position Lp is smaller than the absolute value of the last print position Ep minus the right end print position Rp, and if the judgment results in YES, that is, when the movement of the carriage 22 from the last print position Ep to the left print position Lp is shorter in path than the movement to the right end print position Rp, processing proceeds to S14 (printing control of shortest path). For example, such a case is as shown in Fig. 4(e). In S14, according to the left end print position Lp and data of the present position memory 51, the print head 27a (i.e. the carriage 22) is moved to the print position higher by one character (in the direction of left margin) than the left end position Lp. In the following S15, line feed processing is performed which feeds the print paper 15 by an amount of a set line space. Furthermore, in S16, the print head 27a is moved to the left end print position Lp (refer to Fig. 4(e)). In S17, according to data of the print direction flag 53, judgment is made on whether or not the preceding print has been made in the right direction, that is, the present data of the print direction flag 53 is "1". In this case, the data of the flag 53 is "1", and therefore processing returns to S6. When the data of the print direction flag 53 is not "1", processing moves to S18, and when the data of the flag 53 is inverted (if the flag data is "1", it is changed to "0", and if "0", to "1"), and processing returns to S6. On the other hand, if the judgment results in NO in S13, that is, when the movement of the carriage 22 from the last print position Ep to the right end print position Rp is shorter in path than the movement to the left end print position LP, processing proceeds to S19. For example, such a case is as shown in Fig. 4(b). In S19, according to the right end print position Rp and data of the present position memory 51, the print head 27a is moved to the print position lower by one character (in the direction of right margin) than the right end print position Rp. In the following S20, line feed processing is performed which feeds the print paper 15 by an amount of a set line space. In S21, the print head 27a is moved to the right end print position Rp (refer to Fig. 4(b)). Then, in S22, judgment is made on whether or not the preceding print has been made in the right direction, and if it has been made in the right direction, processing proceeds to the above-mentioned S18, and if in the left direction, processing returns to S6. In S12, if the judgment is NO, that is, when it is judged that the last print position Ep is not located between the left end print position Lp and the right end print position Rp, positional errors of the carriage 22 is not required to be regulated, and therefore processing proceeds to S23. For example, as shown in Fig. 4(a), (c) and (d), the last print position Ep is not located between the left end print position Lp and the right end print position Rp of the line segment S. In S23, judgment is made on whether or not the absolute value of the last print position Ep minus the left end print position Lp is smaller than the absolute value of the last print position Ep minus the right end print position Rp, and if the judgment results in YES, that is, when the movement of the carriage 22 from the last print position Ep to the left end print position Lp is shorter in path than the movement to the right end print position Rp (printing control of shortest path), processing proceeds to S15. For example, such a case is as shown in Fig. 4(d). Also, if the judgment results in No, that is, when the movement of the carriage 22 from the last print position Ep to the right end print position Rp is shorter in path than the movement to the left end print position Lp, processing proceeds to S20. For example, such a case is as shown in Fig. 4 (a) and (c). Then, when the print direction becomes left and flag data "0" is written to the print direction flag 53, printing is controlled through S6 - S23 likewise the case of printing in the right direction. This means that, for example, in the case of Fig. 4(g), control of printing in both directions is performed including regulation of positional errors of the carriage 22 through S6 - S18, and in the case of Fig. 4(j), control of printing in both directions is performed including correction of positional errors of the carriage 22 through S6 - S13 and S19 - S22. In the case of Fig. 4 (f) and (h), control of printing in both directions is performed without regulation of positional errors of the carriage 22 through S6 - S12, S23 and S15 - S18, and further in the case of Fig. 4(i), control of printing in both directions is performed without regulation of positional errors due to backlash and wire elongation of the driving means of the carriage 22 through S6 - S12, S23 and S20 - S22. When all text data of the text memory 52 are printed, judgment is made to be YES in S8, and processing proceeds to S24, print completing processing is executed which clears data of the print buffer 54, and processing returns to S2. In addition, if judgment is made to be NO in S5, processing proceeds to S25, and alarm processing such as buzzer sounding is performed, and processing returns to S2. In S3, if the judgment results in NO, that is, when a key other than the print start key 11 is operated, processing proceeds to S26, and the processing corresponding to the operated key is executed, and processing returns to S2. As described above, in the case where printing in both directions is performed on a print line basis on a plurality of lines including printing control of shortest path and the last print position Ep is located between the left end print position Lp and the right end print position Rp of the succeeding print line, when the print head 27a is moved to the left end print position Lp, the print head 27a is moved to the print position of one character higher order than the left end print position Lp, thereafter being moved to the left end print position Lp, and when the print head 27a is moved to the right end print position Rp, the print head 27a is moved to the print position of one character higher order than the right end print position Rp, thereafter being moved to the right end print position Rp. Therefore, each character to be printed on each print line is printed by moving the carriage 22 in the same direction. This means that the intervals between characters on the same line are kept constant and thereby beautiful print of document can be performed. In addition, in the above-described embodiment, in order to regulate positional errors caused by a play of gears or elongation of a wire in the driving means of the carriage 22, when the print head 27a is moved, the print head 27a is moved by an amount with one extra character and thereafter moved back by one character to the normal position, but the extra amount of movement is not limited to one character, and in short, the amount of movement has only to be enough to regulate the positional errors in the carriage driving system. In the control of printing in both directions in the above-mentioned first embodiment, when printing is made on the succeeding print line by reversing the print direction, the carriage 22 is moved with a predetermined extra amount set, and thereafter the carriage 22 is moved back by the predetermined amount in the reverse direction, and therefore an effect of backlash thereafter is prevented and the intervals between characters are kept constant. However, actually, when printing is made on the succeeding print line with the printing direction reversed, the print position of each character on the succeeding print line deviates from that on the preceding print line. This means that each print position of printing in the left direction after printing in the right direction deviates right from each print position of printing in the right direction. Also, each print position of printing in the right direction after printing in the left direction deviates left from each print position of printing in the left direction. In order to prevent this positional deviation, such a configuration may be adopted that a control routine of printing in both directions in the first embodiment is modified partly as shown in Fig. 5, and when the printing direction is reversed after the above-described regulation of positional errors has been made, the amount of rotation of the carriage drive motor 90, that is, the amount of correction of backlash and wire elongation is controlled so that the print position of each character to be printed in the left direction (or right direction) corresponds to the print position of each character to be printed in the right direction (or left direction). Then, description is made on a control routine of this modified printing in both directions with reference to a flow chart in Fig. 5. In S18, data of the print direction flag 53 is inverted, and processing proceeds to S30. In S30, judgment is made on whether or not the data of the print direction flag 53 has been inverted from "1" to "0", that is, whether or not the printing direction has been inverted from right to left, and when the judgment results in YES, processing proceeds to S31. In S31, the carriage drive motor 90 is driven to make reverse rotation by an amount of rotation of the carriage drive motor 90 during which the carriage 22 is not moved actually despite the rotation of the carriage drive motor 90 (amount of regulation of the positional errors), and the print head 27a is moved in the left direction by a predetermined distance, and processing proceeds to S6. When the judgment results in NO in S30, that is, when the data of the print direction flag 53 is inverted from "0" to "1", processing proceeds to S32. In S32, the carriage drive motor 90 is driven to make forward rotation by an amount of regulation of the positional errors, and the print head 27a is moved in the right direction by a predetermined distance, and processing proceeds to S6. Thus, characters can be printed on predetermined positions without apparent deviation on all print lines. In addition, the amount of regulation of the positional errors may be obtained by measuring the distance of actual positional deviation, being stored in the ROM 40 as data, or may be arbitrarily set by the operator. These control routines of printing in both directions are not limited to the flow charts as shown in Figs. 3(a) to 3(c) and Fig. 5, but they may be modified partly to routines as shown in Fig. 6 (a) and (b). Second Embodiment (Fig. 1, Fig. 7 and Fig. 8) This second embodiment is an embodiment in the case where the present invention is applied to a typewriter like the electronic typewriter 1 in the above-mentioned first embodiment, and therefore description thereon is made using the same numerals and symbols for designating the elements having the same function as that of the electronic typewriter 1 of the above-mentioned first embodiment. Next, description is made on the whole configuration of the control system of the electronic typewriter based on a block diagram in Fig. 7. Basically, the electronic typewriter 1 is constituted with the keyboard 3, the printing mechanism PM, the displaying mechanism D, the controlling apparatus CA, and the keyboard 3, the printing mechanism PM and the displaying mechanism D are connected to the CPU (Central Processing Unit) 130 of the controlling apparatus CA through a bus 131 including data bus and address bus. To one input port of the CPU 130, a cover switch 80 for detecting the state of opening and closing of the cover 4 for shutting the top opening part of a space wherein the carriage 22 moves is connected by a connecting wire 81, and the other end of the cover switch 80 is grounded, and the intermediate part of the connecting wire 81 is connected to a 5V reference voltage line Vc through a pull-up resistor 82. Then, when the cover 4 is closed, the cover switch 80 is closed and a "L"-level signal is inputted to the input port, and when the cover 4 is opened, the cover switch 80 is opened and a "H"-level signal is inputted to the input port. The controlling apparatus CA is constituted with the CPU 130, the ROM (Read Only Memory) 140 and the RAM (Random Access Memory) 150 connected to the CPU 130 through the bus 131. A program memory 41A of the ROM 140 stores in advance a control program for controlling the printing mechanism PM and the displaying mechanism D in correspondence to code data inputted from each character key 10 and various function keys 13, 14 on the keyboard 3, a control program for setting the original positions of the typewheel 24 and the carriage 22 in the state that the carriage 22 is brought in contact with a stopper 95 in the vicinity of the left-side wall of the frame 2, a printing control program for making printing in both directions while the carriage 22 is moved forward and backward on a print line basis, a control program for controlling correction of the backlash and wire elongation as described later, and the like. The RAM 150 is provided with the present position memory 151 for sequentially renewing and storing the present position of the carriage 22 (i.e. the present position of the print head 27a) from the absolute origin in correspondence to the print position, a key buffer 162 for temporarily storing data which is inputted from the keyboard 3 or is read from the text memory 152, a line buffer 160 for storing data of at least one print line from the key buffer 162 or the text memory 152 in correspondence to the print position, a relocation position memory 161 for storing data of the last print position, the print direction flag 153 which is set when the print direction is right and is reset when the print direction is left in printing text data of the text memory 152. In addition, the text memory 152 stores EOT (End of Text) code following the last data thereof. The CPU 130 makes the printing mechanism PM print characters and symbols corresponding to data inputted from each character key 10, and simultaneously makes the line buffer 160 sequentially store that data in correspondence to the print position based on the control program in the typewriter mode. Furthermore, in the memory mode, the CPU 130 makes the line buffer 160 store inputted data of one print line, and simultaneously makes the displaying mechanism D display it, and makes the text memory 153 store that one line of data in response to an operation of the return key 12. The displaying mechanism D has a general configuration comprising the display 75 consisting of a liquid crystal displaying apparatus and a display controller 73A outputting a drive signal to the display 75. Next, description is made on a flow chart of positional error regulating control performed by the controlling apparatus CA of the typewriter 1 with reference to Fig. 8(a) and Fig. 8(b). In addition, the description is made by exemplifying a memory dumping processing routine dumping text data stored in the text memory 152 in a manner of printing in both direction. First, an area, that is, a name of file storing desired text data to be printed is specified by operating the character key 10 and function keys 13, 14. Then, when the print start key 11 is operated to print the inputted data stored in the text memory 152, the main routine is started, and processing proceeds to step 1 (hereinafter represented simply as S1, and the same is true of the other steps), and judgment is made on whether or not the character data to be printed is stored in the specified file of the text memory 152, and if the judgment is YES, processing proceeds to S2, and if the judgment is NO, processing proceeds to S3, and alarms the operator by a buzzer, returning to the main routine. In S2, text data of one print line stored in the text memory 152 is written to the line buffer 160, and processing proceeds to S4. In S4, whether or not the cover 4 is opened is judged based on an open/close signal from the cover switch 80, and if the judgment is NO, that is, when the "L"-level signal is given, processing proceeds to S5, and text data of one character is read from the line buffer 160, and processing proceeds to S6. Then, in S6, judgment is made on whether or not that text data is the end data (the EOT code data or not), and if the judgment results in NO, processing proceeds to S7, and judgment is made on whether or not that data is line end code data (for example, line feed code), that is, printing of one print line has been completed, and if the judgment is NO, processing proceeds to S8, and characters corresponding to the text data are printed. At this time, the CPU 130 outputs a signal to each drive circuit of the printing mechanism PM. In the following S9, based on the print direction flag 153, the print head 27a is moved right when the flag 153 is set and is moved left when the flag 153 is reset by one character, and processing proceeds to S10, and the present position of the print head 27a is stored in the relocation position memory 161, and processing returns to S4. Thus, by repeating S4 - S10, the text data of the line buffer 160 is printed in sequence, and when the data of line end is printed, the line end code data is read from the line buffer 160, and if the judgment results in YES, processing returns to S2. Then, the following text data of one print line is stored in the line buffer 160, and S4-S10 are repeated likewise the above-mentioned, and the text data is printed in sequence. In addition, where the text data is the line end code data, the print direction flag 153 is changed-over from set to reset or from reset to set, and thereby the print direction is reversed. When the cover 4 is opened in the course of printing the text data to perform a work such as replacing the print ribbon 26 or the typewheel 24, the cover switch 80 is opened, and the "H"-level signal is sent to the CPU 130, and in S4, judgment is made to be YES, and processing proceeds to S11. In S11, processing waits until the print ribbon 26 is replaced and the cover 4 is closed again, that is, until the "L"-level signal is outputted from the cover switch 80 to the CPU 130, and when the cover 4 is closed and the "L"-level signal is outputted to the CPU 130, processing proceeds to S12. In S12, the original position of the carriage 22 is set by moving the carriage 22 and bringing it in contact with a stopper 95 in the vicinity of the left-side wall of the frame 2, and the original position of the typewheel 24 is set by rotating the typewheel 24 in the state of contact with a stopper (not shown), and thereafter processing proceeds to S13. In S13, based on data of the relocation position memory 161, the print head 27a is moved to the relocation position, and processing proceeds to S14. In addition, description on mechanical and electric configurations and controls thereof for setting the original positions of the carriage 22 and the typewheel 24 are similar to the printwheel homing apparatus disclosed in U.S. Pat. No. 4,264,220 or U.K. Pat. Application No. 8800171. In S14, based on the print direction flag 153, whether or not the print direction is left is judged, and the judgment results in YES in the case of left direction (the print direction flag 153 is reset), and processing proceeds to S15. In S15, the print head 27a is moved to the print position lower (right side) by one character, and processing moves to S16, and regulation of backlash and wire elongation is performed by moving the print head 27a to the print position higher (left side) by one character again, and processing proceeds to S5, and printing is resumed from the relocation position halfway of printing. In addition, when the print direction is right, regulation of backlash and wire elongation is not required, and therefore judgment is made to be NO, and processing proceeds to S5. Thus, when the text data is printed and the last text data is printed, the end data (EOT code data) is read, and processing proceeds to S17, and ending processing such as clearing of the line buffer 152 is performed, and thus processing goes through a routine of dumping processing, returning to the main routine. Thus, where a work such as replacement of the ribbon 26 is performed by opening the cover 4 when the print direction is left and then the cover 4 is closed, the print head 27a is returned to the relocation position after regulation of the positional errors due to backlash and wire elongation, and therefore the character intervals on the place where printing is resumed can be kept constant likewise the case where the printing direction is right, and thereby accurate printing can be made. In addition, in this embodiment, configuration is made in a manner that the original position of the carriage 22 is set by bringing the carriage 22 in contact with a stopper 95 in the vicinity of the left-side wall of the frame 2, but configuration may be made in a manner that the original position is set by bringing the carriage 22 in contact with a stopper in the vicinity of the right-side wall of the frame 2, and in this case, after suspending the printing by opening the cover 4 when the printing direction is right, regulation of positional errors is performed. In addition, in this embodiment, configuration is made in a manner that printing is suspended and resumed based on the open/close signal of the cover 4, but configuration may be made in a manner that printing is suspended based on a detection signal from a ribbon end detecting means when the print ribbon 26 runs out, and printing is resumed when the restart key is operated. In this case, when the print ribbon 26 runs out, the "H"-level signal is sent to the above-mentioned input port of the CPU 130, and when the restart key is operated, the "L"-level signal is sent to that port. In addition, the above-mentioned ribbon end detecting means can be constituted with an aluminum reflecting foil affixed to the ribbon end and a light emitter and a photoreceptor which are installed in the carriage 22 so as to correspond to the aluminum reflecting foil. In addition, as shown in the Japanese Patent Application No. 61-269371 filed by the applicant of the present invention, it is also possible that when the cover 4 is opened, printing operation is suspended instantly, and when the cover 4 is closed, the above-mentioned control of regulation of positional errors is performed by interrupt processing, and printing is continued from the print position following the lastly printed position. It is needless to say that the present invention is applicable also to various printers having a gear mechanism in the carriage driving system such as thermal-head type printers, wire-dot type printers, ink-jet type printers and laser printers besides the daisy-wheel type typewriter of the above-mentioned embodiment.

Claims: A printing apparatus (1) comprising: memory means (52) for storing code data of characters to be printed so as to correspond to each print position; printing means (PM) having a print head (27a) mounted on a carriage (22); carriage driving means (CM) for driving the carriage (22) along a print line for printing on a print paper characters corresponding to the code data stored in the memory means (52); and printing direction control means (30, 40, 50) for controlling movement of the carriage (22) forward or backward while printing along each print line so that the carriage (22) moves along a shortest path; characterised in that the printing apparatus (1) further comprises: judging means (30, 41, 51) for judging, according to data in the memory means (52), whether or not the print end position of a present print line (F) is located between a print start position and a print end position of a succeeding print line (S); and control means (30, 40, 50) for controlling the carriage driving means (CM) to move the carriage (22), when said print end position of the present print line (F) is located between the print start position and the print end position of the succeeding print line (S), to a preceding print position which precedes the print start position in the print direction of the succeeding print line (S) and subsequently to move the carriage (22) in the print direction to the print start position. A printing apparatus (1) according to claim 1, wherein the control means (30, 40, 50) comprises a print direction flag memory (53) for storing print direction information. A printing apparatus (1) comprising: memory means (52) for storing code data of characters to be printed so as to correspond to each print position; printing means (PM) having a print head (27a) mounted on a carriage (22); carriage driving means (CM) for driving the carriage (22) along a print line for printing on a print paper characters corresponding to the code data stored in the memory means (52); print direction control means (130, 140, 150) for controlling movement of the carriage (22) forward or backward while printing along each print line so that the carriage (22) moves along a shortest path; and original position setting means (95, 130, 140) for setting an original position of said carriage (22) at one movement limit position; characterised in that the printing apparatus (1) further comprises: print suspending means (80, 130, 140) for controlling the printing means (PM) to suspend printing in accordance with a suspension command signal; print resuming means (130, 140) for controlling movement of the carriage (22), when the print suspending means (80, 130, 140) is released, to a print resuming position at which printing is to be resumed, after setting of the carriage (22) to the original position by the original position setting means (95, 130, 140); and regulating means (130, 140, 150) for regulating backlash in the carriage driving means (CM) before resuming printing, when the direction of movement of the carriage (22) from the movement limit position to the print resuming position is reverse to the print direction in which printing is to be resumed, by moving the carriage (22) from the print resuming position in a direction opposite to that in which printing is to be resumed and then returning it to the print resuming position by moving it in the direction in which printing is to be resumed. A printing apparatus (1) according to claim 3, wherein the suspension command signal is output to the print suspending means (80, 130, 140) upon opening of a cover (4) covering an upper opening of a space in which the carriage (22) is arranged to move forwards and backwards. A printing apparatus (1) according to claim 3 or 4, wherein said original position setting means (95, 130, 140) is arranged to set an original position of the carriage (22) by contacting the carriage (22) with a stopper (95) installed near a side wall of a frame (2) of the printing apparatus (1). A printing apparatus (1) according to any of claims 3 to 5, wherein the printing means (PM) is provided with a typewheel (24), and the original position setting means (95, 130, 140) further includes means for setting an original position of said typewheel (24).

Inventors: SASAKI, RYOICHI C/O BROTHER KOGYO KABUSHIKI KAISHA, SATA, YOUJI C/O BROTHER KOGYO KABUSHIKI KAISHA
Applicants: BROTHER KOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: B41J19
IPC codes: B41J19