ROTARY CHARACTER-CARRYING MEMBER AND SELECTOR DEVICE THEREFOR FOR A PRINT UNIT IN TYPEWRITERS

Abstract: A print unit for an electronic typewriter comprising a removable character-carrying disc (15) with flexible spokes (47) which is operated by a selector motor which in turn is controlled by a control circuit. The character-carrying disc (15) is provided with a plurlaity of reflective identification plates (204) and a recognition circuit detects the pattern of the reflective plates (204) present in selected ones of a series of predetermined angular sectors (205) of the disc (15) to identify some characteristics of the disc (15), e.g. typing pitch and character set. The angular position of the disc (15) is detected by a position transducer which generates a position signal for the control circuit having a period which is double the angular distance between two contiguous character-carrying spokes (47), discriminating the spokes (47) at even positions from those at odd positions. In an initialisation phase, a zeroing circuit coarsely positions the character-carrying disc (15) in a zero area defined by a synchronization plate (203) adjacent a plate-free gap (206) and activates the control circuit to stop the character-carrying disc (15) in a zero position in respect of a spoke (47) having a predetermined parity. The print unit is provided with phase regulation elements for the position transducer and for the circuit for recognition of the reflective plates (204) on the character-carrying disc (15).

Description: The present invention relates to a rotary character-carrying member and the selector device therefor for a print unit of typing machines and in particular electronic typewriters, according to the preamble of claim 1 and claim 9, respectively. Typewriters which use character-carrying members with identification elements are generally provided with a detection or recognition circuit which, in an initialisation phase of the machine, provides for rotary movement of the character-carrying member and for recognition of some characteristic parameters of the character-carrying member, thus simplifying use of the machine. An arrangement of the above-described type is known from e.g. GB-A- 1 604 577 in which the character-carrying member is of the daisywheel type, in which the motor shaft is rotated by a stepping motor and in which the circuit for recognition of the identification elements detects the coded position of the identification elements, recognises a particular reference position of the character-carrying member and activates the motor for a number of steps such as to position the character-carrying daisywheel in its zero position. That arrangement requires a recognition circuit which has a high degree of angular resolution and positioning of the identification elements which is so accurate as to discriminate the reference position with a maximum error that is less than half the angular step of the character-carrying petals. This is necessary in order to avoid the zero position of the daisywheel being associated with a different petal from the predetermined petal, and causes the character-carrying daisywheel and the recognition circuit to be therefore rather expensive. Another disadvantage of this arrangement is that it is unreliable with regard to correct initialisation. Any error in the reading of the identification elements causes errors in the setting of the character-carrying daisywheel and associated apparatus which cannot readily be corrected. The object of the present invention is to provide a character-carrying member provided with identification elements, and the selector device therefor, which are reliable and of restricted cost both individually and jointly. The invention in its various aspects is defined in the appended claims to which reference should now be made. That problem is solved in a preferred selector arrangement embodying the invention which comprises a position transducer having a movable portion which moves in synchrony with the character-carrying member and a detection portion which generates a position signal having a periodic angular distance which is double the angular spacing of two adjacent characters of the character-carrying member. The character-carrying member has coded indentification elements in a circular array which include both editing elements and check elements. The editing elements are associated with a calculated control code obtainable in accordance with a predetermined rule by a recognition processor circuit, for control of a setting circuit to rotate the character-carrying member into its reference position, and for setting other parameters of the typewriter. The check elements provide a control code at least to check the correct setting of the character-carrying member in its zero position. The setting circuit which is controlled by the recognition circuit coarsely positions the character-carrying member in a zero region associated with the reference positions of the character-carrying member, and a servo mechanism which is controlled by the position signal from the position transducer precisely stops the character-carrying member in a zero position which is unambiguously associated with the zero region and with a character thereof of predetermined positional parity. In addition to the identification elements for generating an identification code, the daisywheel also has coded elements for generating a reference control code. This permits the electronic circuits of the typewriter to accept the identification code only if the reference control code is checked and found to be equal to a control code calculated unambiguously by the electronic circuit from the identification code of the character-carrying daisywheel. The character-carrying member may be of the daisywheel type and the position of the identification elements detected by a suitable detection member which generates a corresponding presence signal when an identification element is in front of the detection member. This member is mounted on a support which provides for angular regulation with respect to the print hammer. That makes it possible to modify the position of the detection member with respect to the character-carrying daisywheel, and thus also modify the phase of the presence signal with respect to a position of alignment of the character-carrying spoke with respect to the print hammer. The character-carrying daisywheel preferably comprises reflective identification plates as identification elements, and a reflective phasing or timing plate associated with the zero position. Each identification plate occupies an angular sector of constant width and the phasing or timing plate occupies an angular sector of an extent which is substantially less than that occupied by an identification plate. Besides the initialisation means which detect the presence of coded identification elements for defining the zero position of the character-carrying member, the preferred selector device also comprises a second initialisation means which define the zero position of the character-carrying member independently of the first initialisation means. Other means are provided to detect non-reading of the phasing element and/or non-recognition of the identification code in order to activate the second initialisation means. The selector device may comprise a transducer which provides a periodic position signal of variable amplitude, in response to the rotation of the character-carrying member from given reference positions, and of a periodic angular distance which is equal to double the angular pitch of the characters. A motor has its rotor connected to the character-carrying member for rotation thereof and a discrimination circuit activates the selector motor for a positive direction of rotation upon an increase in the position signal for the characters having a given position parity and activates the selector motor for a negative direction of rotation upon an increase in the position signal for the characters of opposite parity. A preferred embodiment of the invention is set forth in the following description which is given by way of non-limiting example and with reference to the accompanying drawings in which: Figure 1 is a partial longitudinal view of a typewriter using a print unit with the character-carrying member and the selector device according to the invention, Figure 2 shows a partial front view of some details from the Figure 1 construction, Figure 3 shows a partial longitudinal view in section on an enlarged scale of some details from the Figure 1 construction, Figure 4 shows a partial front view of the character-carrying member of Figure 1 on an enlarged scale, Figure 5 shows a partly exploded longitudinal view of some details from Figure 1, Figure 6 shows a partial front view of some details from Figure 5, Figure 7 shows another partial view of the selector device according to the invention, Figure 8 shows a block circuit diagram of the control circuit of the selector device according to the invention, Figure 9 shows a diagram representing some signals of the circuit shown in Figure 8, Figure 10 is an operating diagram of the circuit shown in Figure 8, Figure 11 is a diagram showing other signals of the circuit illustrated in Figure 8, and Figure 12 is a representative layout of some elements of the character-carrying member shown in Figure 4. Referring to Figure 1, the typewriter according to the invention comprises a platen roller 11 and a print unit formed by a carriage 12 which is movable on a cylindrical guide 13 parallel to the roller 11 and on a second guide which is not shown in the drawings. The carriage 12 carries a selector device 14 for a character-carrying member 15 or 46 of the disc or 'daisywheel' type, and a print hammer or striker 16. The carriage 12 comprises two side members 17 and 18 which are parallel to each other and orthogonal to the axis of the cylindrical guide 13. The translatory movement of the carriage 12 in front of the platen roller 11 is controlled in known fashion, for example as described in our published European patent application EP-A-0 122 039. A frame 19 which is disposed between the side members 17 and 18 of the carriage 12 is of such a shape as to have two side members 21 which support a plate 22 parallel to the platen roller 11 and on which are mounted the hammer 16 and the selector device 14. The side members 21 of the frame 19 are fixed to two bushes 23 which are mounted coaxially to the cylindrical guide 13 inside the side members 17 and 18 of the carriage 12. In that way the frame 19 is pivoted with respect to the cylindrical guide 13 and follows the movements of the carriage 12 in front of the platen roller 11. A single bush 23 and a single side member 21 can be seen in the drawings. The frame 19 and the plate 22 can rotate through 16° approximately with respect to the cylindrical guide 13, as described in above-mentioned patent application EP-A-0 122 039. The selector mechanism 14 comprises an electrical dc motor 26 which is capable of rotating in the clockwise and anticlockwise directions. The motor 26 has a shaft 27 on which there is fixed a pinion 28 that is always engaged with a toothed wheel 29 mounted on a sleeve 31 on a shaft 33. The angular positions of the shaft 33 are detected by a transducer 36 comprising a synchronisation disc 32 fixed on the shaft 33 and provided with a series of transmitting windows 34 disposed adjacent to the circumference thereof, a collimator or an illuminating means 37 and a photodetector 38, which are disposed on opposite sides with respect to the path of movement of the windows 34. The shaft 33 is rotatable in a flange 39 (see Figure 5) of a container 40 which is mounted in such a way that it can be angularly adjusted by means of three screws 53 disposed at 120° to each other, housed in respective slots 54 in the plate 22. Only two screws 53 and two slots 54 can be seen in the drawings. Figure 6 shows a detail of the slots 54 in the plate 22 for the screws 53. A sleeve 41 (see Figure 5) is fixed on the shaft 33 and comprises front-mounted coupling means 42 capable of coupling with corresponding coupling means 43 on an adaptor disc 44 mounted on the character-carrying disc 15 or 46. The disc 46 is of known type, for example of the type described in Italian patent No 1 016 552 granted to the present applicants on 20th June 1977, and comprises a central hub 45 (see Figure 1) and a hundred radial and flexible spokes or 'petals' 47 which carry a respective print character 48 at their ends. A gripping portion 49 having a front wall 51 is fixed to a front surface 52 of the central hub 45. The adaptor disc 44 is of known type, for example of the type described in European patent application EP-A-0 118 277. The disc 44 is of plastics material and is of such a configuration as to couple on the one hand with the hub 45 of the character-carrying disc 15 and on the other hand with the sleeve 41. More particularly, the disc 44 comprises two pairs of hooks or catches (not shown in the drawings) which project perpendicularly and which are arranged to engage into respective cavities 56 (see Figure 4) in the character-carrying disc 46 to connect the two discs 44 and 46 together, as described in above-mentioned patent application EP-A-0 118 277. A cylindrical peg 56 for angular positioning is arranged to co-operate with the hole in the character-carrying disc 46 for angularly positioning the disc 44 and the character-carrying disc 15 or 46 relative to each other. Provided on the outside periphery of the adaptor disc 44 is a seat 58 for receiving a tooth 59. The tooth 59 is elastically connected to a frame 60 (see Figure 7) for lifting a correction ribbon 55 which can be lifted by a control element 50 of the type described in European patent application EP-A-0 118 317 and is part of the arrangement for the zero positioning operation described in European patent application EP-A-0 229 764. A tray member 61 (see Figure 1) of plastics material is disposed substantially vertically between the frame 19 and the platen roller 11. The tray member 61 is of substantially parallelepipedic shape, being hollow internally, for housing the character-carrying disc 46. The tray member 61 is laterally provided at its bottom with two lugs 62 of which only one is shown in the drawings and which are each pivoted on a pin 63 on the frame 19. The tray member 61 further comprises two ribs 64 and 66 (see Figures 1 and 2), each of which has a seat 67 for housing a leg 68 of a lever 69. The lever 69 is constantly urged towards the ribs 64 and 66 on the tray member 61 by a spring 71 formed by a steel bar, the ends of which are engaged to two vertical legs 72 of which only one is shown in the drawings and which are disposed at the sides of the tray member 61. The lever 69, by means of the end 70 and the element 75, normally bears against the front part 51 of the gripping portion 49 to maintain the coupling between the portions 41 and 42 during the rotary movement of the daisywheel 15. The lever 69 is provided with a lower leg 73 (see Figure 3) housed in a seat in the tray member 61 and an upper leg 76 which is capable of engaging a projection 77 on a plate portion 78, in turn provided with two legs 79 for engaging a vertical plate portion 81 of the lever 69. An intermediate support 91 of plastics material has a pin 92 which can be housed in a seat 93 in the lever 69 and supports a photoelectric pair 89 comprising, in side-by-side relationship, an illuminating element 90 and a photosensing element 94, which are housed in a seat or opening 95 in a front wall 100 of the tray member 61. The photoelectric arrangement 89 is part of a recognition circuit carried by a printed circuit 96 of which components 97 and 98 have been shown. The intermediate support 91 is fixed to the lever 69 by means of an eccentric screw 99 having a nut 101 and a recording sector 102, which permit the photoelectric arrangement 89 to change its angular position with respect to the character-carrying disc 15. The electronic typewriter as described hereinbefore may alternatively mount character-carrying daisywheels 46 (see Figure 7) of the type which is already known or daisywheels 15 which are substantially identical to the disc 46 but which are further provided with reflective identification plates 106 (see Figure 4) disposed in a coded fashion in twenty five sectors of a circular ring 109 on the front wall 52. The machine further comprises a transparent cover 107 which, when it is closed, protects the region in which the carriage 12 moves in front of the platen roller 11 and which acts on a microswitch 108. Any replacement of the daisywheel 15 or 46 requires the cover 107 first to be opened, and causes the production of a signal COVER by the microswitch 108. Setting of the above-described structure is effected in the following manner: In order to provide the proper phase relationship between the selector device 14 (see Figure 1), the character-carrying disc 15 or 46 and the striker hammer 16, by means of an electronic control member 170 and for a selection cycle as described hereinafter, the motor 26 is operated which, by means of the pinion 28 and the toothed wheel 29, rotates the synchronisation disc 32 and the daisywheel 15 or 46. The optical transducer 36 detects the movement of the windows 34 therepast and the control circuitry 170 rotates the character-carrying disc 15 or 46 until the signal from the transducer thus assumes a reference zero value. One of the one hundred petals 47 will then be coarsely positioned in front of the typing point 103. A check is now made to ascertain whether the axis of the hammer 16 is aligned with the axis of the selected character 48. In the situation which can be easily envisaged that the above-mentioned axis is not in an aligned condition, the three screws 53 (Figure 5) are slackened off and the container 40 together with the selector device 14 and with the daisywheel 15 or 46 is rotated with respect to the plate 22 in a clockwise or anticlockwise direction until the axis of the hammer 16 (Figure 1) coincides with the axis of the character 48. At that point the three screws 53 (see Figure 5) are locked and the character which is positioned in front of the typing point 103 or any other character which is similarly selected will be perfectly aligned with the axis of the hammer 16. Subsequently, the position of the photoelectric arrangement 89 (see Figure 3) is regulated by means of the eccentric screw 99. For that purpose, a 'specimen' daisywheel (not shown in the drawings) comprising a single petal and a single reflective zone 106 is fitted in position. The daisywheel is disposed in front of the arrangement 89, the illuminating element 90 is supplied with a predetermined current and the current at the photosensor element 94 is detected. The nut 101 is then slackened and, by means of the registration sector 102, the eccentric screw 99 is rotated. The support 91 is thus rotated in a clockwise or anticlockwise direction together with the photoelectric arrangement 89 and the printed circuit 96, thus modifying the relative angular positioning as between the arrangement 89 and the reflective plate. The rotary movement as between the arrangement 89 and the 'specimen' daisywheel continues until there is detected at the photosensor 94 a preset current value which conventionally increases in response to an anticlockwise rotation of the support 91, indicating that only the input or leading edge of the plate is aligned with the arrangement 89. That value is intermediate between the maximum value associated with the presence of a reflective plate precisely aligned with the arrangement 89, and the minimum value associated with the absence of reflective plates. When that intermediate value is attained, the nut 101 is locked and the recognition circuit is set. Under operating conditions, the signal at an intermediate value from the element 94 is such as to activate a circuit 109 (see Figure 8) for switching to zero a signal REMAIN that is normally at high logic level. Selector motor control The motor 26 is servo-controlled by the electronic circuit 170 of the machine (Figure 8) comprising a microprocessor 171 with a central processing unit 168 connected to an input-output unit 169 and a print control unit (PCU) 172. The input-output unit 169 receives and/or transmits signals from the input members of the machine such as the keyboard and other external memory units and receives other signals such as inter alia the signal REMAIN coming from the photosensor 94 and the signal COVER coming from the microswitch 108. The unit 172 controls the motor 26 by means of an integrated logic-analog circuit (IC) 173 and a switching-type feeder 174 substantially as described in our European patent application EP-A-0 102 248 and European patent application EP-A-181 742. Briefly, the feeder 174 feeds the motor 26 with a current whose magnitude depends on the relationship between two pulses of opposite signs, PW1 and PW2 of a frequency which is fixed and high with respect to the activation times of the motor and of variable relative duration. The pulses PW1 and PW2 are obtained from a pulse Q of a pulse modulator (PWM) 182, the duration thereof in turn being controlled by a decoder 183 of the circuit 170, in response to the state of three logic signals M1, M2 and M3. The relationship between PW1 and PW2 is variable in a range of between 0 and 0.5 for a first direction of movement or between 0.5 and 1 for a direction of movement which is opposite to the first, in per se known manner. The two ranges are determined by the instantaneous state of the signals M1 and M2. The pulse modulator 182 receives feedback signals from the photodetector transducer 38 and from the motor 26 and defines the value of the relationship between the signals PW1 and PW2 in the range determined by the signals M1 and M2. For that purpose, the modulator 182 is connected to the photodetector 38 by way of a preamplifier 181, an amplifier 184, an amplifier 185 and a dynamic limiter 186, and to the stator circuit of the motor 26 by way of a current sampling resistor 187. The fifty transmissive windows 34 in the synchronisation disc 38 are equally spaced from each other. Due to the effect of irradiation by the illuminating means 37 and the rotary movement of the disc 32, the output signal A from the pre-amplifier 181 on the output side of the photodetector 38 is thus trapezoidal. The amplifier 184 subtracts from the signal A a reference signal VR and provides a signal FTA (see Figure 9) which is symmetrical with respect to VR, also being trapezoidal, whose amplitude, in the vicinity of the position of alignment of each petal with respect to the hammer, is proportional to the angular displacement of the petal with respect to its position of alignment. The signal FTA, in response to a clockwise rotation of the character-carrying daisywheel 15 or 46, presents fifty rising edges 188 (see Figure 9) and fifty falling edges 189, so that the periodic angular distance of the signal FTA is double the angular distance between two adjacent petals of the daisywheel 15 or 46. The angular spacing between the two edges 188 and 189 is therefore equal to the angular spacing between the axes of two adjacent spokes 47 of the daisywheel 15 or 46. The reference voltage VR is also regulated in such a way that two contiguous zero points Xo and X'o of the signal FTA of the two edges 188 and 189 correspond to the angular spacings between the axes of two adjacent petals 47 of the daisywheel 15 or 46. The dynamic limiter 186 (Figure 8) limits the amplitude of the signal FTA at the input to the amplifier 185, to a preset value. Below the maximum value, the signal at each edge 188 is substantially proportional to the angular displacement of each petal at an 'even' position with respect to the position of alignment with the hammer, while the signal of each edge 189 is substantially proportional to the opposite or reverse of the angular displacement of each petal in an odd position. The decoder 183, in response to the low state of the signal M3, can produce a signal T which sends the dynamic limiter 186 into a condition of saturation, independently of the value of FTA and, in response to a particular state of the signals M1 and M2, supplies a signal G which modifies the gain of the amplifier 185. A squaring circuit 198 supplies a squared signal STA corresponding to the movement of each petal in front of the position of alignment with the hammer (FTA = Ø) and the control circuit 172 responds to the edges of the signal STA selectively to generate an interrupt signal INT (see Figure 9) for the microprocessor 172 (see Figure 8). The values of M1, M2 and M3 are up-dated in response to processing operations internal to the circuit 172 and in response to fresh information received by the microprocessor 171. In addition the rising and falling edges of the signal STA in turn represent the moment at which the respectively even and odd petals pass in front of the hammer 16. As described in above-mentioned patent application No EP-A-0 102 248, the state of the signals M1, M2 and M3 determines the following conditions: When the petal of the character 48 to be selected is far from the print position, M3 is at level 1, the signal T puts the dynamic limiter 186 into a condition of saturation and the signal Q of the modulator 182 supplies current pulses whose maximum value is determined by a reference signal VRC, in the direction of movement fixed by the microprocessor 171. Control of the motor is thus of time-dependent digital type. The configuration of the signals M1 and M2 is varied in the varying periods of time between different angular steps, in dependence on the difference in time between the actual time of passage in the preceding period and a theoretical time which is read in a memory ROM 190 of the microprocessor 171. The theoretical times in the ROM 190 are preset in dependence on the number of angular steps to be performed and provide acceleration phases and braking phases in order to minimise the total selection time. A movement command in accordance with the actual direction of movement of the motor causes acceleration. In contrast, a movement command which is not in accordance with the actual direction of movement causes braking of the motor. In the situation indicated as short circuit, the motor is subjected to a weak braking action independently of the direction of rotation thereof. The signals M1 and M2, even in the period between the two edges of the signal STA, are generally variable. A first phase of each digital control in the period between two signals INT provides for acceleration or braking substantially as far as half the angular step between two petals and takes account of the difference between the actual time of passage and the theoretical time in the preceding period between two INT and due to a movement which is respectively slower or faster than the theoretical movement. That phase is followed by a short circuit phase until the theoretical time has elapsed. In the case where the motor in the current period has been slower than the speed envisaged, the circuit 172 immediately detects that there has been a lag and immediately generates a pair of values M1 and M2 which causes acceleration in advance of the motor, aimed at making up the lag. That process continues until the penultimate petal passes in front of the striker. At that time, the circuit 172 generates for a fixed time a pair of values M1 and M2 which permit the petal of the desired character to reach an approximate print alignment zone, up to about half a step from the striker. The circuit 172 then immediately switches the signal M3 to zero and activates an alignment phase with a particular configuration of the signals M1 and M2. The signal M3 = 0 puts the signal T to zero and the signal FTA can modify the input signal of the pulse modulator 182 by way of the limiter 186 and the amplifier 185 so that the current in the motor 26 is proportional to the angular displacement of the petal from its position of alignment. The control of the motor is therefore of analog-positional type. The correspondence of fifty windows 34 with the one hundred petals 47 of the daisywheel 15 or 46 has the consequence that, according to whether a petal of 'even' position or a petal in an 'odd' position is disposed in front of the hammer, the edges of the signal FTA are inclined in opposite directions. Figure 11 relates the characters at even positions 221 with the signal STA. The microprocessor 172, in each character selection phase subsequent to the initialisation phase which will be described hereinafter, controls the positional parity of the character to be typed or printed. Upon switching of M3=0 in the region in which the signal FTA is the same, the microprocessor 172 imposes on the signals M1 and M2 a configuration which is dependent on the positional parity in respect of the petal in an aligned condition. If the desired character is in a conventionally even position, the signals STA and FTA are rising in response to a clockwise rotation of the daisywheel and the movement stops at the point Xo in Figure 9. In that condition, the microprocessor 171 imposes a configuration M1=0 and M2=0 and a current of conventionally positive sign at the motor 26 for each positive value of FTA. If the desired character is in an odd position, the signals STA and FTA are falling in response to an anticlockwise rotation of the daisywheel and the movement stops at the point X'o and the microprocessor 172 imposes the configuration M1=1, M2=0 and a negative current at the motor 26 for each positive value of FTA. In that way the rising and falling zero points Xo and X'o respectively of the signal FTA are both stable points of the servo mechanism. Character-carrying daisywheel with reflective plates In accordance with the invention, the plates 106 (see Figure 4) comprise a phase timing or synchronisation plate 203 (indicated at 1 in Figure 12) which occupies an angular sector which is congruent with that of three character-carrying petals 47, a sector 202 of four petals (indicated at 2 in Figure 12) which is without plates, and a group of other plates 204 (from 3 to 19 in Figure 12) which can occupy selected ones of seventeen contiguous angular sectors 205 of a coded zone and in which each sector 205 is congruent with a sector of four petals 47. The remaining portion which corresponds to five sectors of four petals and one sector of five petals (from 20 to 25 in Figure 12) is in contrast without plates and defines a non-reflective space (gap) 206 between the synchronisation plate 203 and a last position 207 along the circular ring or array. The sectors of the coded zones, which are left without the reflective plates, outside the gap 206, are in any case fewer than six consecutive sectors. When the setting phases have been completed in the manner already described above, for each petal 47 in a position which is even and a multiple of four aligned with the hammer, the photosensor 94 detects the condition of illumination of a part of one of the twenty five sectors in which the plates 106 can be positioned. Alignment with the hammer of the even petals which are not a multiple of four corresponds to alignment with the input or leading edge (for a clockwise rotary movement) of the sector for positioning of the plates 106. Under those conditions, for the odd petals and for the even petals with a position which is a multiple of four (indicated by 215 in Figure 11), the output signal of the circuit 109 generates the signal REMAIN = 0 when a reflective plate is present and the signal REMAIN=1 in the absence of a plate, including in the situation where the plates are displaced from their theoretical position with respect to the positioning sectors. The signal REMAIN will be of an ambiguous value dependent on the phase displacement of the plates with respect to the theoretical position, for the petals at even positions which are not a multiple of four (indicated at 214 in Figure 11). For illustrative purposes Fig 11 is drawn for the case in which the first few sectors 205 are alternatively with and without plates. The seventeen coded positions define thirteen bits which form an identification code and four bits which form a reference control code. The plates of the identification code are subdivided into three groups of which a first group 208 of three bits (A, B, C) (Figure 12) represents the spacing pitch of the characters 58 (for example 1/10", 1/12", 1/15", PS), a second group 209 of three bits (A, B, C) represents the mean dimensions of the characters and influences the mean strength of striking, and a third group 210 of seven bits (A, B, C, D, E, F, G) is indicative of the linguistic grouping to which the daisywheel belongs. The reference control code of a fourth group of plates 211 represents in binary code the sum of the bits REMAIN=1 contained in the three groups of plates 208, 209 and 210. The initialisation phase indicated at 219 in Figure 10 follows a state of zeroing of the memories RAMs 191 of the microprocessor 171. The ROMs 190 of the microprocessor 171 comprise locations intended for a program which produces the initialisation phase in accordance with the following steps: Block 220 for seeking the rising edge of the signal STA. The program activates a configuration M1=1, M2=0, M3=0 for a predetermined period of time (3.2 msec) which tends to cause the synchronisation disc to reach a position Xo in an anticlockwise direction, after passing through the short-circuit state M1=0, M2=1, M3=1, for a second fixed period of time (4.8 msec), and subsequent return to positional control M1=1, M2=0, M3=0. The initialisation program also provides a waiting state and a short rotary movement in a clockwise direction, which is controlled in respect of time, to ensure that the synchronisation disc is not incorrectly stopped at the point X'o which is intrinsically unstable in the configuration M1=0, M2=1. That rotation is followed by a series of cycles which alternate the positional control in the configuration M1=1, M2=0, M3=0 with the short circuit state M1=0, M2=1, M3=1. At the end, the program stops the disc in the configuration M1=0, M2=1, M3=0, corresponding to a condition of alignment of petals of even positions in front of the striker and a positional control associated with a state of low gain of the amplifier 185 and low current in the motor 26. In that state, the daisywheel is stopped in a position such that the photosensor 94 receives the light from one of the reflective plates, it is it present and is in the appropriate phase, and sets the signal REMAIN=0, or the photosensor does not receive any light and the signal REMAIN=1, in the case where there is no plate in the stop position, or the edge of the plate is out of position. In the block 221, the program proceeds with a rotary movement of two petals in a clockwise direction with a digital control at low speed, and the subsequent reading of REMAIN. The operation is repeated until (block 222) REMAIN=1 is read for 12 times, indicating that the gap 206 has been identified. If the gap has not been found, the program continues to rotate the daisywheel until a timer (junction 225) signals that the time intended for that phase has elapsed; in that case the program proceeds to start a mechanical zeroing cycle 226 which will be described hereinafter. When the gap 206 has been found in the block 223, the program provides a further rotary movement of two petals and reading of REMAIN. If it is found (junction 224) that REMAIN=0, that indicates in an unambiguous fashion that the daisywheel which is fitted in position has the reflective synchronisation plate 207 after the gap 206 and that that plate associated with the positioning petal number 32 has been identified. If that is not the case, the time control (block 229) activates the mechanical initialisation cycle 226. In the case where the signal petal 32 has been identified, the program also causes a rotary movement of four petals in a clockwise direction (block 228) for reading REMAIN=1 in the central zone of the sector 202 which is without plates. Subsequently (block 229 and junction 230), the program performs seventeen cycles each comprising a rotary movement in an anticlockwise direction corresponding to four petals for alignment of the petals at positions which are a multiple of four and reading REMAIN (block 231). The program proceeds (block 231) with arithmetic summing of the number of bits REMAIN=1 which are read in the three groups of plates 208, 209 and 210, and compares the number calculated in that way to the code which is read in the group 211 (junction 232). In the case where the code read and the code calculated are not the same, the program proceeds to activate the mechanical initialisation cycle 226. In the case of the codes being the same, the program transfers the codes read into the RAM 191 (block 233) and proceeds with a rotary movement of four petals in an anticlockwise direction (block 234) to a position of alignment of the petal with the underlining character (_), zero position, in front of the striker. Finally, the program (block 235) resets the registers of the RAMs 191 which are representative of the angular position of the daisywheel. The structure of the reflective plates as defined hereinbefore, in combination with correct positioning of the synchronisation disc 32 permits the daisywheel to be put into its zero position, even if the plates are displaced from their theoretical position by an angle of up to more or less half the angular step or pitch of the petals 47. That function is carried out by the dimension of the plate 203 which is reduced in comparison with that of the other plates 106. As already described in the initialisation phase, by the effect of initially stopping the daisywheel in one of the rising zero points Xo of the signal FTA, a petal of conventionally 'even' position is aligned in front of the striker 16. In the phase for recognition of the gap 206, the program proceeds to read REMAIN only as a consequence of incremental rotary movements of two petals in correspondence with the petals at even positions. Reading of the zone 206 which is without plates gives rise to an operation of counting twelve bits REMAIN=1 in the case where the last plate of the sector 211 corresponding to the petal in position 6 in Figure 12 is present and had given rise to a signal REMAIN=0 at the output or trailing edge. In the case on the other hand where only the first plate of the group 211 is present, corresponding to the petal in position 94, and its output or trailing edge had given rise to a bit REMAIN=1, the count will be equal to nineteen. In both cases the operation of reading at the plate 207 with recognition of the signal REMAIN=0 in correspondence with alignment of the petal in position 32 will take place reliably over a zone of the plate 207 which excludes the edges, in a theoretical reading position which is spaced one petal from its input edge and two petals from its output edge. Reading of the plate 207 is thus reliable even if the plate were displaced in a clockwise direction as far as almost one petal and as far as two petals in an anticlockwise direction. When recognition of the gap has been confirmed, the subsequent operation of reading the other plates is effected by incremental rotary movements equal to four petals. The operation of reading the other plates thus occurs at the respective central zones and permits a positioning tolerance equal to almost two petals in the two directions of rotation. Figure 11 puts in phase relationship the state of the signal STA and the signal REMAIN, with the reading operations in respect of the logic blocks 221 and 222 in Figure 10 and associated respectively with the petals in even positions and the petals in positions which are a multiple of four. That result was made possible by virtue of using a synchronisation disc which, having a periodic angular distance congruent with the angular distance between two petals, makes it possible to discriminate parity of position of the petals and to carry out the initialisaion operation on only petals at even positions. In accordance with a second embodiment of the invention, the reflective synchronisation plate could also be of a width which is equal to that of the other plates. In order to avoid any uncertainty in regard to reading at the edge of the plates, all the plates would therefore have to be displaced by a petal with respect to the position in the first embodiment. Identification of the synchronisation plate would be effected in a similar manner to that described hereinbefore. The subsequent operation of reading the code will therefore take place every four petals, corresponding to the petals at odd positions, after a jump of five petals. In that case, tolerance in regard to positioning of the plates would be limited to a single petal both in regard to the synchronisation plates and in regard to the coded plates. The presence of the control code in the zone 211 finally ensures that any accidental event which modifies the state of the signal REMAIN with respect to its theoretical value cannot introduce wrong information regarding the daisywheels which are actually used in the print unit of the typewriter. Mechanical initialisation In the case where the control code of the daisywheel 15 has not been recognised or the time intended for the optical recognition operation has elapsed, the program activates the mechanical initialisation cycle 226 which is similar to that described in our above-mentioned patent application EP-A-0 119 764. The initialisation cycle 226 follows the stoppage of the daisywheel 15 or 46 at a point Xo of the synchronisation disc 32 (block 220) and provides (block 240) for lifting of the correction ribbon 55 and resilient contact of the tooth 59 against the cylindrical surface of the adaptor disc 44. The program then provides a command for rotary movement in the anticlockwise direction equal to two petals (block 241). If the tooth 59 has not entered the recess 58, the rotary movement of the daisywheel may take place freely, and the program detects the start of two edges of the signal STA (junction 242) and activates a positional-type stop command (block 243). The same occurs if a time greater than that provided for that phase (junction 243) has elapsed. The program proceeds with a programmed rotary movement at low speed and in a clockwise direction without time control for 101 annular increments (block 244). The program then continues with lowering of the corrector ribbon 55 (block 248) and consequential disengagement of the tooth 59 from the recess 58 and with zeroing of the registers of the RAMs 191 (block 233), either in the case of recognition of the one hundred edges of the signal STA (junction 245 and junction 246), indicative either that it is already in the zero position and that there has been rebounding or bouncing as between the tooth 59 and the recess 58, or in the case where the daisywheel has stopped, edges of the signal STA have not occurred and the timer has detected the elapsing of a period of time greater than that provided for. In that case also, the use of a synchronisation disc having a periodic angular distance double that of the petals makes it possible substantially to increase the tolerances in respect of the recess 58 and the tooth 59 and the degree of reliability of the initialisation arrangement.

Claims: A removable character-carrying disc (15) for a print unit (12) c of a typewriter, comprising a plurality of spokes (47) carrying a font of characters (48), a hub (45) supporting the spokes (47), and provided with an array of coded identification elements (106) disposed along a circular array and including check elements (211) and editing elements (208,209,210) for identifying a zero position of the disc and characteristic parameters of the characters carried by the spokes, and wherein the character-carrying disc (15) is provided to be used in a typewriter comprising a motor shaft (33) which can be connected to the hub for rotation of the disc, a recognition circuit (109) and reading means (89) for detecting the presence of the coded elements in given angular positions of the disc, and generating respective presence signals (REMAIN), and processor circuit means (169,171) responsive to the presence signals (REMAIN) and setting circuit means (172,173,174) actuable for setting the typewriter according to the characteristic parameters and rotating the character-carrying disc (15) into a reference position, characterised in that the editing elements (208,209,210) are associated with a calculated control code according to a given checking rule, the calculated control code being obtainable by the processor circuit means (169,171) of the typewriter in response to presence signals (REMAIN) of the editing elements and according to the given checking rule; and in that the check elements (211) represent a reference control code for the editing elements, the reference control code being comparable by the processor circuit means (169,171) of the typewriter with the calculated control code for verifying the correct reading of the editing elements and actuating the setting circuit means. A character-carrying disc according to claim 1, characterised in that the array of coded identification elements (106) comprises a plurality of reflective plates (204) to be read by a photoelectric pair formed by an illuminating element (90) and a detection element (94) of the reading means (89). A character-carrying disc according to claim 2, characterised in that the reflective plates comprise three groups of plates (208,209,210) which identify three characteristic parameters of the disc, and a fourth group of plates (211) which identifies the group of check elements. A character-carrying disc according to claim 2 or 3, characterised in that the reflective plates (204) each occupy a constant angular width and the plates also comprise a section (206) without plates, which precedes a phase plate (203), and a further section (202) without a plate, unambiguously associated with a zero position of the character-carrying disc, wherein the hub has means for being coupled with the motor shaft of the typewriter in a plurality of predetermined positions, wherein the phase plate is recognizable by the recognizing circuit of the typewriter after recognizing the sector without the predetermined number of plates in order to set a zero position of the disc. A character-carrying disc according to any of the preceding claims, characterised in that each one of the editing elements (208,209,210) occupies a constant angular sector being that of a fixed number (4) of spokes (47). A character-carrying disc according to any of the preceding claims, characterised in that the editing elements (208,209,210) concern items of information relating to the spacing pitch (PS) of the characters, the mean dimension of the characters and the linguistic group to which the character-carrying disc belongs. A character-carrying disc according to any of the preceding claims, characterised in that the calculated control code represents a binary code indicative of the number of presence signals (REMAIN) generated upon detection of the editing elements (208,209,210), and the reference control code represents that number in binary notation. A character-carrying disc according to both claims 3 and 7, characterised in that the fourth group of plates (211) comprises plates in different positions along the array to represent in binary notation the absolute number of plates (208,209,210) present in the three groups. A selector device for a character-carrying printing machine disc (15) of the type comprising a plurality of spokes (47) carrying the characters (48), a hub (45) supporting the spokes and an array of coded identification elements (106) disposed along a circular array, and including an identifyable gap (206) defining a gap location, a phase timing element and editing elements (208,209,210) identifying a zero position of the disc, and characteristic parameters of the characters, respectively, and also comprising check elements (211), the device comprising a motor shaft (33) which can be selectively positioned in a plurality of angular positions and which is capable of being removably connected to the character-carrying disc (15) for selection of the characters to be printed, setting circuit means (172,173,174), first initialisation means comprising means for rotating the disc for a given time, reading means (89) for detecting the presence of the elements in given angular positions of the character-carrying disc, and a recognition circuit (109) operatively connected to the reading means for defining a zero position of the character-carrying disc in response to recognition of the phase timing element and the editing elements, characterised in that the character-carrying disc (15) further provides zero identifying means independent of the phase timing element, in which the editing elements (208,209,210) are associated with a respective calculated control code according to a given checking rule, and wherein the check elements (211) represent a reference control code for the editing elements and wherein the selector device further comprises: processor circuit means (169,171) for obtaining the calculated control code in response to presence signals (REMAIN) from the editing elements and according to the given checking rule; the processor circuit means (169,171) obtaining the reference control code in response to presence signals from the check elements and comparing the reference control code with the calculated control code in order to verify the correct reading of the editing elements and actuate the setting circuit means (172,173,174); second initialisation means (59) which define the zero position of the character-carrying disc (15) in response to identification by the zero identifying means, independently of the first initialisation means; and means which detect the non-reading of the phase timing element and/or non-recognition of the identification code for activating the second initialisation means. A selector device according to claim 9, characterised in that the zero identifying means of the character-carrying disc comprises a stop element (58) in a given angular position of the character-carrying disc; the first initialization means further comprise means for rotating the character-carrying disc through a first rotation (221) for detection of the presence of the phase timing element and the coded identification elements; wherein timing-out means (227) are provided for detecting that the zero position has not been identified by the first identification means, during the first rotation, and for activating the second initialization means (59) for further rotation after a predetermined period of time; and wherein the second initialization means comprise a counter-element stop (59) which can be activated to interfere with the stop element (58) for stopping the character-carrying disc in the zero position, means for rotation of the character-carrying disc (244,245,246,247,248,235) to perform at least one complete revolution of the character-carrying disc, and setting the selector device in an operative status defining the sole zero position of the disc. A selector device according to claim 9 or 10, characterised by a transducer having a movable portion (32) synchronous with the motor shaft (33) and a detection portion (38) which generates a position signal (A) having a periodic angular distance which is double the angular spacing of two adjacent characters of the character-carrying disc, and in that the setting circuit means (172,173,174) functions as a zeroing circuit which coarsely positions the character-carrying member (15) in a zero region associated with the reference position and by a servo mechanism (173) which is controlled by the position signal (A) of the transducer (32,38) and which precisely stops the character-carrying member in a zero position which is unambiguously associated with the zero region and with a character of predetermined positional parity. A selector device according to claim 9, 10 or 11, further comprising a print hammer (16), means (42,43) for coupling the motor shaft to the character-carrying disc in a plurality of predetermined positions for selection of a spoke in front of the hammer and a detection member (94) for detecting the presence of one of the identification elements, characterised in that the detection member (94) is mounted on a support (91) such as to provide angular adjustment with respect to the hammer (16) to modify the position of the detection member with respect to the character-carrying member in correspondence with a position of alignment of the spoke with respect to the hammer and for modifying the phase of the presence signal (REMAIN) with respect to the position of alignment of the spoke.

Inventors: BOELLA, MARCELLO, FIGINI, MARIO
Applicants: ING. C. OLIVETTI & C., S.P.A.
Application year: 1986
Main classification: B41J1
IPC codes: B41J1, B41J7