CA1170374A - High speed character writer - Google Patents
High speed character writerInfo
- Publication number
- CA1170374A CA1170374A CA000398069A CA398069A CA1170374A CA 1170374 A CA1170374 A CA 1170374A CA 000398069 A CA000398069 A CA 000398069A CA 398069 A CA398069 A CA 398069A CA 1170374 A CA1170374 A CA 1170374A
- Authority
- CA
- Canada
- Prior art keywords
- carriage
- voltages
- platen
- stylus
- character
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/485—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes
- B41J2/49—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes by writing
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM]
- G05B19/4181—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM] characterised by direct numerical control [DNC]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
Abstract
HIGH SPEED CHARACTER WRITER
Abstract of the Disclosure The character writer disclosed herein is of the calligraphic type in which a pen or stylus traces out each character, positioning of the pen within the character region being accomplished by a pair of servomechanisms responsive to control voltages to provide movement along transverse axes. The pen and servomechanisms are themselves carried on a carriage which can be traversed along a platen. Character writing while the carriage is moving is accomplished by generating, for each character, a voltage which is proportional to carriage displace-ment within a character region and is combined with at least one of the servomechanism control voltages thereby to create a moving frame of reference which is essentially independent of carriage velocity.
Abstract of the Disclosure The character writer disclosed herein is of the calligraphic type in which a pen or stylus traces out each character, positioning of the pen within the character region being accomplished by a pair of servomechanisms responsive to control voltages to provide movement along transverse axes. The pen and servomechanisms are themselves carried on a carriage which can be traversed along a platen. Character writing while the carriage is moving is accomplished by generating, for each character, a voltage which is proportional to carriage displace-ment within a character region and is combined with at least one of the servomechanism control voltages thereby to create a moving frame of reference which is essentially independent of carriage velocity.
Description
I i70374 1 Background of the Invention The present invention relates to a calligraphic writer and more particularly to such a device in which writing is per-formed from a moving carriage on which the pen driving servo-mechanisms are mounted.
Calligraphic character writing systems are known in which a pen or stylus together with driving servomechanisms are transported on a carriage from character position to character position and, as each position i8 traversed, the servomechanisms are energized by respective control voltages to effect tracing out of the desired character. Such devices are described for example in U.S. Patents Nos. 3,182,126; 3,342,936 and 3,3~9,176 to Ascoli et al; and ~.S. Patent No. 4,150,902 to Brescia. A
related form of graphical plotter is shown in U.S. Patent No.
3449,754 to Stutts.
As is understood, the vectors or line segments which make up a chara~ter will typically be stored in digital form in digital memory devices. So-called read only memories are usually preferred, packaged in a form which permits them to be easily exchanged, e.g. to effect the changing of character fonts. In t~e prior art character writing or printer systems as disclosed, however, it appears that the carriage is moved from ~ne position to the next and stopped to allow writing of each character. This then permits the vectors which typically make up each character to be defined with respect to a fixed frame of reference. While the possibility of writing while the carriage is moving has been suggested e.g. in the Brescia patent, no structure implementing this function is disclosed. Clearly, writing from a moving '~
1 carriage has a substantial advantage in total throughput of the machine since the time spent accelerating and decelerating the carriage is deducted from the time available for writing. This loss of time sets an upper limit on the ~verall speed of the device which limits throughput no matter what improvements are made in the speed of the servomechanisms which drive the pen and stylus. As will be understood by those skilled in the art, the coding of vectors in digital form could be implemented 80 that the vector orientations themselves take into account the moving frame of reference. In this way the character resulting from writing from a moving carriage would have the desired shape not-withstanding th~ moving frame of reference. However, as will also be appreciated by those skilled in the art, such a compen-sation would be fixed in the original coding of each character and would be valid for a single carriage speed only.
Among the several objects of the present invention may be noted the provision of a high speed calligraphic character writer; the provision of such a character writer in which writing is effected from a carriage while the carriage is in motion; the provision of such a writer in which writing is performed by a stylus driven in transverse directions by a pair of servomotors carried on a carriage which is moving at a freely selectable velocity; the provision of such a system which i8 highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.
1 Summary of the Invention Briefly, the present invention involves a character writer in which each of a series of successive characters is represented by a plurality of digital data words, each word defining a vector. The writer employs a mechanism which writes on a platen from a carriage which is traversed across the platen.
A pair of linear transducers are carried on the carriage for moving a stylus in essentially transverse directions, thereby permitting movement of the stylus within a predetermined region relative to the carriage. Means are provided for driving the carriage across the platen at a selectable speed and for genera-ting a voltage which varies in proportion to displacement of the carriage, starting from a preselectable point corresponding to the edge of a character location along the platen. A pair of voltages are generated from each of the data words, which volt-ages represent velocity components along the transverse direction. A pair of integrators are provided for generating, from the velocity voltages, respective relative position voltages. The carriage displacement voltage is summed with at least one of the relative position voltages, thereby to obtain respective control voltages representative of position with respect to the carriage. The transducers are driven to effect stylus movement which is, relative to the carriage, proportional to the control voltages and which is, relative to the platen, proportional to the relative position voltages and is essentially independent of the velocity of the carriage.
Brief Description of the Drawings Fig. 1 is a diagram of a calligraphic writing mechanism used in the present invention;
~ ~7037~
1 Fig. 2 is a schematic diagram of control circuitry employed in operating the mechanism of Fig. 1 in accordance with the present invention; and Fig. 3 is a block diagram of a generalized microcom-puter system appropriate for providing data to the circuitry of Fig. 2 and for generally supervising operation of the apparatus.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Description of the Preferred Embodimen~
Referring now to Fig. 1, a carriage mechanism is indi-cated generally by reference character 11. Carriage 11 is slideably mounted on a pair of rails 13 and 15 so as to be moveable along a platen, indicated generally by reference character 17. Platen 17 may, for example, be of the character of a typewriter roller through a fixed platen, independent of the paper feed mechanism, could also be used.
Carriage 11 carries a pair of linear transducers or servomotors 21 and 23 which are adapted for moving or positioning a pen or stylus 25. The servomotors are oriented for moving the stylus 25 along essentially transverse axes. The servomotor 21 moves the stylus along an axis parallel to the carriage motion (the X-axis) while the servomotor 23 moves the stylus along the transverse or vertical axis (the Y-axis). Each of the linear transducers 21 and 23 is responsive to a control signal for mov-ing the stylus along the respective transverse axis and includes also means for generating a feedback or position signal. In the presently preferred embodiment, optical feedback transducers are ~ 170374 1 employed, similar to those described in the Brescia patent iden-tified earlier. Carriage 11 will typically also include a third drive mechanism (not shown) for loading and unloading the stylus to effect writing or not and to vary the loading on the stylus.
At the outset, it may be noted that writing is effected by moving the carriage along the platen 17 from character posi-tion to character position and writing in each character position by energizing the linear servomechanisms 21 and 23 to move the stylus 25 along in accordance with a set of vectors defining the character. The definition of these vectors is preferably stored in diqital form in a suitable digital memory, e.g. a so-called read only memory, which may be readily interchanged to effect changing frorn one font to another. The stylus 25 may be in the form of a pen to effect direct writing or, preferably, will press through a carbon film ribbon to effect writing on paper supported by platen 17.
Carriage 11 is moved along the length of platen 17 by a d.c. servomotor 27 which drives a timing belt 29 passing over a pair of rollers 31 and 33. This is the means for providing move-ment along a row of characters, i.e. in the horizontal direction.Movement of the paper in the transverse direction, e.g. vertical, is provided by means of a stepping motor 35 which rotates the - roller platen 17.
In order to provide a feedback mechanism for sensing movement of the carriage and for keeping track of its position, the servomotor 27 is provided with a shaft encoder 37. Encoder 37 is of the type providing squarewave signals in phase quadra-1 1 7037~
1 ture, as indicated at A and B, so that both motor speed anddirection of rotation can be determined. These positional infor-mation signals are provided to the overall control processor of Fig. 3 as control signals as well as to the servo control cir-cuitry of Fig. 2.
As indicated previously, the definitions of the vectors which make up each character are preferably stored in digital form in a read only memory and are then utilized by a micropro-cessor controller to generate the actual data which controls the stylus-driving servomechanims and the carriage drive. The general organization of this microprocessor system is illustrated in Fig. 3. The system illustrated is bus-oriented, that is, memory devices, I/0 ports, and the processor are all connected to a common data and control bus. This bus is indicated generally by reference character 41, the processor itself being indicated at 43. In one embodiment of the invention, processor 43 was an Intel 8085 microprocessor and the memory and I/0 components were implemented using integrated circuits from the same family of devices. As is understood, the advantage of using a microprocessor-driven controller is that the mode of operation may be flexibly changed under software control, without extensive hardware redesign. In implementing its control function, the processor utilizes random access memory for storing operating parameters, such memory being indicated by reference character 45. Fixed data, i.e. data defining the vectors which make up each character in a font, is stored in so-called read only memory, such memories being indicated in Fig. 3 at reference characters 46-49.
~ 170374 1 Digital data for defining the operation of the control circuitry of Fig. 2 is provided from the microprocessor system through latched output ports 51 and 52. Port 51 provides data for the pen servos while the port 52 provides carriage speed information. As is common to such systems, various control signals are needed by the processor to determine the state of the mechanism and various control signals are provided out to the mechanism controllers. A bi-directional port for this purpose is indicated by reference character 53. A third I/O port 54 is pro-vided for vertical control, i.e. the controller which drives the stepping motor 35. However, this mechanism forms no part of the present invention and is not disclosed in detail herein.
Preferably, the vector defining data is stored in terms of direction and length of vector. Among the functions performed by the microprocessor system of Fig. 3 is to expand the data and generate respective X- and Y-axis components. These values are specified to four bits of accuracy each and are applied, respect-ively, to the digital to analog converters (DACs) 61 and 63 of Fig. 2. The values provided to the control circuitry represent velocity components. To get displacement values, the voltages obtained from the DACs 61 and 63 are integrated by the circuits indicated at 71 and 73, respectively~ Each of these circuits comprises an inverting amplifier and an integrating capacitor, Cl and C3, respectively. The capacitors Cl and C3 can be dis-charged, i.e. to reset the integrators, by means of respective analog switches. The dual analog switch which performs this function, together with its control circuitry, is as indicated generally by reference character 75. The resetting switch cir-1 17037q 1 cuitry 75 is operated by a control signal, designated ~ESET,which is one of the signals obtained from the control port 53 of the microprocessor controller of Fig. 3.
The output signals from the integrators 71 and 73 are applied, through respective current-limiting resistors Rl and R3, to error amplifiers 75 and 77. The error amplifiers 75 and 77 are responsive to the difference between the integrator output signals and the respective position signals obtained from the X
and Y linear servomechanisms 21 and 23. The error amplifiers, in turn, drive, in conventional fashion, X- and Y-axis power ampli-fiers 76 and 78.
The quadrature output signals obtained from the shaft encoder 37 are each applied to one input of a respective com-parator 81 and 83. A suitable intermediate reference voltage is applied to the other input of each comparator. The output from comparator 81 is applied directly as one input to an exclusive OR
gate 85 and, in delayed form, as the other input to gate 85. The delay is effected by a filter comprising a resistor R6 and capa-citor C6, with s~uaring up being performed by a buffer gate 87.
The function of this delay and gating circuitry is to provide, at the output of gate 85, a brief pulse for each transition, posi-tive or negative, in ~he input signal A. A completely similar circuit provides, in re~ponse to the input signal B, a corresponding pulse train at the output of an exclusive OR gate 89. The pulse trains obtained from the gates 85 and 89 are com-bined in an exclusive OR gate 91. The output of this gate comprises a pulse for each transition in either of the input signals (A or B). In effec~, a factor of four multiplication in 1 17037~
1 the pulse rate is provided as compared with the pulse rate of either one of the input signals. If the carriage were driven by a stepper motor instead of the d.c. servomotor 27, the pulse signal used to advance that motor might be used in place of the pulse train generated by the shaft encoder 37.
The pulse train obtained from the gate 91 is applied to a counter 101 so that the counter generates a digital value which varies in proportion to displacement of the carriage. This counter 101 is reset along with the resetting of the integrators 71 and 73 at the start of each character. Thus, the digital value held by the counter in one sense represents displacement across the character position. The digital value in counter 101 is converted to an analog signal voltage by a digital to an~log (D/A) converter 103, the transfer being buffered by a latch 105 which is loaded in synchronism with the counting to minimize ripple-through effects. In one sense, the output voltage from the D/A converter 103 comprises a ramp as the carriage moves across the platen. This ramp voltage, however, is not a time dependent function in the usual sense, but rather is proportional to actual displacement of the carriage and thus, in the time domain, will vary as the speed of the carriage varies.
The rarnp voltage obtained from D/A converter 103 is mixed in or summed with the X axis position signal obtained from the integrator 73, the ramp ignal being applied, through a resistor R9, to a summing junction S at the input of error amplifier 77. The addition of this carriage displacement com-ponent into the vector-defining voltage allows the writing of characters from the moving carriage without requiring alteration 1 of the basic vector encoding scheme and, in a manner, allowing the velocity of the carriage to change. Because of this compen-sation, the carriage can be driven re~atively rapidly when simple characters are being written and more slowly for more complex characters. In this way, the throughput of the machine can be substantially increased as compared with the situation which would exist if the speed of the carriage had to be kept constant, as would be the case if compensation were built into the vector encoding scheme. In such a case the single speed chosen would have to be relatively low, i.e. selected to permit forming of the most complex character to be written.
Selection of carriage speed is performed by the micro-processor system of Fig. 3, a data word representing the desired carriage speed being output through the port 52. This data, at five bits of accuracy, is applied to a digital-to-analog con-verter 111. The output signal from converter 111, which is an analog voltage representing desired speed, is compared with a voltage representing actual speed. This latter voltage is obtained by a frequency-to-voltage converter 113 driven by the pulse train from gate 91. As described previously, the pulse in this train is generated at a rate which is proportional to the speed of the carriage, being derived from the shaft encoder asso-ciated with the carriage drive motor 27. The output voltages from the frequency-to-voltage converter 113 and the ~/A converter 111 are applied, through respective mixing resistors Rll and R13, to a summing junction T to derive an error signal. This error is amplified as indicated at 117. The amplified error signal is mixed with an a.c. component obtained from a dither oscillator 1 119 at the input of an amplifier 121 which, in turn, drives a power amplifier controlling the servomotor 27.
The embodiment illustrated includes provision for forming characters of different sizes from the same font data, i.e. the digital data being applied directly to the digital-to-analog converters 61 and 63. For this purpose, the converters are of the so-called multiplying type in which the output voltage is proportional, not only to the digital value applied, but also to an analog reference voltage. A four bit data word, again obtained from the microprocessor controller of Fig. 3, is applied to a decoder 72 which generates two separate one-of-four selec-tion signals. Each of these set of signals is applied to a respective quad switch 74 and 76 to select one of four predeter-mined voltages for application, as a reference voltage, to the respective digital analog converter 61 or 63. The predetermined voltages are obtained from a voltage divider comprising resistors R21-R24. The resistors R21-R24 are selected to produce voltages corresponding to desired typesizes rather than to perform a nor-mal digital-to-analog conversion. The nature of the decoding is such that only one switch in each of the packages is on at any one time so that the reference voltage applied to each digital-to-analog converter 61 or 63 may be independently selected.
Accordingly, since the horizontal and vertical scaling factors can be selected separately, characters of different aspect ratios can be formed from the same data as well as merely scaling the characters.
In the embodiment illustrated, the axis o~ one of the linear servotransducers driving the stylus is parallel to the ~ 17037.~
1 direction of carriage movement and the other axis is essentially perpendicular thereto. Accordingly, the displacement based com-pensation signal only needs to be mixed with one of the two control signals driving the servotransducers in order to obtain the desired moving frame of reference. On the other hand, those skilled in the art will appreciate that an arrangement could be utilized in which the axes of both linear servotransducers were at an angle, e.g. 45 to the direction of carriage movement, though perpendicular to each other. In such a case, displacement compensation components of appropriate magnitude would be æummed with each of the servocontrol signals, observing appropriate polarity. Such an arrangement should be understood to be within the scope of the present invention. Similarly, it should also be understood that it is relative motion between the platen and the stylus mount which is significant and that either component might actually be moved even though movement of the stylus mount (carriage) is disclosed in the preferred embodiment.
Summarizing, it can be seen that the present invention facilitates the digital encoding of character defining vectors with respect to a seemingly fixed frame of reference. High speed writing of characters from a moving frame of reference, the carriage, is then accomplished by summing, with at least one of the writing servocontrol voltages, a compensating voltage which -- represents displacement across a character position. Thus, co~-pensation for the moving frame of reference is achieved essen-tially independently of carriage speed.
In view of the foregoing, it may be seen that several o~jects of the present invention are achieved and other advan-tageous results have been attained.
1 As various changes could be made in the above construc-tions without departing from the scope of the invention, it should be understood that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Calligraphic character writing systems are known in which a pen or stylus together with driving servomechanisms are transported on a carriage from character position to character position and, as each position i8 traversed, the servomechanisms are energized by respective control voltages to effect tracing out of the desired character. Such devices are described for example in U.S. Patents Nos. 3,182,126; 3,342,936 and 3,3~9,176 to Ascoli et al; and ~.S. Patent No. 4,150,902 to Brescia. A
related form of graphical plotter is shown in U.S. Patent No.
3449,754 to Stutts.
As is understood, the vectors or line segments which make up a chara~ter will typically be stored in digital form in digital memory devices. So-called read only memories are usually preferred, packaged in a form which permits them to be easily exchanged, e.g. to effect the changing of character fonts. In t~e prior art character writing or printer systems as disclosed, however, it appears that the carriage is moved from ~ne position to the next and stopped to allow writing of each character. This then permits the vectors which typically make up each character to be defined with respect to a fixed frame of reference. While the possibility of writing while the carriage is moving has been suggested e.g. in the Brescia patent, no structure implementing this function is disclosed. Clearly, writing from a moving '~
1 carriage has a substantial advantage in total throughput of the machine since the time spent accelerating and decelerating the carriage is deducted from the time available for writing. This loss of time sets an upper limit on the ~verall speed of the device which limits throughput no matter what improvements are made in the speed of the servomechanisms which drive the pen and stylus. As will be understood by those skilled in the art, the coding of vectors in digital form could be implemented 80 that the vector orientations themselves take into account the moving frame of reference. In this way the character resulting from writing from a moving carriage would have the desired shape not-withstanding th~ moving frame of reference. However, as will also be appreciated by those skilled in the art, such a compen-sation would be fixed in the original coding of each character and would be valid for a single carriage speed only.
Among the several objects of the present invention may be noted the provision of a high speed calligraphic character writer; the provision of such a character writer in which writing is effected from a carriage while the carriage is in motion; the provision of such a writer in which writing is performed by a stylus driven in transverse directions by a pair of servomotors carried on a carriage which is moving at a freely selectable velocity; the provision of such a system which i8 highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.
1 Summary of the Invention Briefly, the present invention involves a character writer in which each of a series of successive characters is represented by a plurality of digital data words, each word defining a vector. The writer employs a mechanism which writes on a platen from a carriage which is traversed across the platen.
A pair of linear transducers are carried on the carriage for moving a stylus in essentially transverse directions, thereby permitting movement of the stylus within a predetermined region relative to the carriage. Means are provided for driving the carriage across the platen at a selectable speed and for genera-ting a voltage which varies in proportion to displacement of the carriage, starting from a preselectable point corresponding to the edge of a character location along the platen. A pair of voltages are generated from each of the data words, which volt-ages represent velocity components along the transverse direction. A pair of integrators are provided for generating, from the velocity voltages, respective relative position voltages. The carriage displacement voltage is summed with at least one of the relative position voltages, thereby to obtain respective control voltages representative of position with respect to the carriage. The transducers are driven to effect stylus movement which is, relative to the carriage, proportional to the control voltages and which is, relative to the platen, proportional to the relative position voltages and is essentially independent of the velocity of the carriage.
Brief Description of the Drawings Fig. 1 is a diagram of a calligraphic writing mechanism used in the present invention;
~ ~7037~
1 Fig. 2 is a schematic diagram of control circuitry employed in operating the mechanism of Fig. 1 in accordance with the present invention; and Fig. 3 is a block diagram of a generalized microcom-puter system appropriate for providing data to the circuitry of Fig. 2 and for generally supervising operation of the apparatus.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Description of the Preferred Embodimen~
Referring now to Fig. 1, a carriage mechanism is indi-cated generally by reference character 11. Carriage 11 is slideably mounted on a pair of rails 13 and 15 so as to be moveable along a platen, indicated generally by reference character 17. Platen 17 may, for example, be of the character of a typewriter roller through a fixed platen, independent of the paper feed mechanism, could also be used.
Carriage 11 carries a pair of linear transducers or servomotors 21 and 23 which are adapted for moving or positioning a pen or stylus 25. The servomotors are oriented for moving the stylus 25 along essentially transverse axes. The servomotor 21 moves the stylus along an axis parallel to the carriage motion (the X-axis) while the servomotor 23 moves the stylus along the transverse or vertical axis (the Y-axis). Each of the linear transducers 21 and 23 is responsive to a control signal for mov-ing the stylus along the respective transverse axis and includes also means for generating a feedback or position signal. In the presently preferred embodiment, optical feedback transducers are ~ 170374 1 employed, similar to those described in the Brescia patent iden-tified earlier. Carriage 11 will typically also include a third drive mechanism (not shown) for loading and unloading the stylus to effect writing or not and to vary the loading on the stylus.
At the outset, it may be noted that writing is effected by moving the carriage along the platen 17 from character posi-tion to character position and writing in each character position by energizing the linear servomechanisms 21 and 23 to move the stylus 25 along in accordance with a set of vectors defining the character. The definition of these vectors is preferably stored in diqital form in a suitable digital memory, e.g. a so-called read only memory, which may be readily interchanged to effect changing frorn one font to another. The stylus 25 may be in the form of a pen to effect direct writing or, preferably, will press through a carbon film ribbon to effect writing on paper supported by platen 17.
Carriage 11 is moved along the length of platen 17 by a d.c. servomotor 27 which drives a timing belt 29 passing over a pair of rollers 31 and 33. This is the means for providing move-ment along a row of characters, i.e. in the horizontal direction.Movement of the paper in the transverse direction, e.g. vertical, is provided by means of a stepping motor 35 which rotates the - roller platen 17.
In order to provide a feedback mechanism for sensing movement of the carriage and for keeping track of its position, the servomotor 27 is provided with a shaft encoder 37. Encoder 37 is of the type providing squarewave signals in phase quadra-1 1 7037~
1 ture, as indicated at A and B, so that both motor speed anddirection of rotation can be determined. These positional infor-mation signals are provided to the overall control processor of Fig. 3 as control signals as well as to the servo control cir-cuitry of Fig. 2.
As indicated previously, the definitions of the vectors which make up each character are preferably stored in digital form in a read only memory and are then utilized by a micropro-cessor controller to generate the actual data which controls the stylus-driving servomechanims and the carriage drive. The general organization of this microprocessor system is illustrated in Fig. 3. The system illustrated is bus-oriented, that is, memory devices, I/0 ports, and the processor are all connected to a common data and control bus. This bus is indicated generally by reference character 41, the processor itself being indicated at 43. In one embodiment of the invention, processor 43 was an Intel 8085 microprocessor and the memory and I/0 components were implemented using integrated circuits from the same family of devices. As is understood, the advantage of using a microprocessor-driven controller is that the mode of operation may be flexibly changed under software control, without extensive hardware redesign. In implementing its control function, the processor utilizes random access memory for storing operating parameters, such memory being indicated by reference character 45. Fixed data, i.e. data defining the vectors which make up each character in a font, is stored in so-called read only memory, such memories being indicated in Fig. 3 at reference characters 46-49.
~ 170374 1 Digital data for defining the operation of the control circuitry of Fig. 2 is provided from the microprocessor system through latched output ports 51 and 52. Port 51 provides data for the pen servos while the port 52 provides carriage speed information. As is common to such systems, various control signals are needed by the processor to determine the state of the mechanism and various control signals are provided out to the mechanism controllers. A bi-directional port for this purpose is indicated by reference character 53. A third I/O port 54 is pro-vided for vertical control, i.e. the controller which drives the stepping motor 35. However, this mechanism forms no part of the present invention and is not disclosed in detail herein.
Preferably, the vector defining data is stored in terms of direction and length of vector. Among the functions performed by the microprocessor system of Fig. 3 is to expand the data and generate respective X- and Y-axis components. These values are specified to four bits of accuracy each and are applied, respect-ively, to the digital to analog converters (DACs) 61 and 63 of Fig. 2. The values provided to the control circuitry represent velocity components. To get displacement values, the voltages obtained from the DACs 61 and 63 are integrated by the circuits indicated at 71 and 73, respectively~ Each of these circuits comprises an inverting amplifier and an integrating capacitor, Cl and C3, respectively. The capacitors Cl and C3 can be dis-charged, i.e. to reset the integrators, by means of respective analog switches. The dual analog switch which performs this function, together with its control circuitry, is as indicated generally by reference character 75. The resetting switch cir-1 17037q 1 cuitry 75 is operated by a control signal, designated ~ESET,which is one of the signals obtained from the control port 53 of the microprocessor controller of Fig. 3.
The output signals from the integrators 71 and 73 are applied, through respective current-limiting resistors Rl and R3, to error amplifiers 75 and 77. The error amplifiers 75 and 77 are responsive to the difference between the integrator output signals and the respective position signals obtained from the X
and Y linear servomechanisms 21 and 23. The error amplifiers, in turn, drive, in conventional fashion, X- and Y-axis power ampli-fiers 76 and 78.
The quadrature output signals obtained from the shaft encoder 37 are each applied to one input of a respective com-parator 81 and 83. A suitable intermediate reference voltage is applied to the other input of each comparator. The output from comparator 81 is applied directly as one input to an exclusive OR
gate 85 and, in delayed form, as the other input to gate 85. The delay is effected by a filter comprising a resistor R6 and capa-citor C6, with s~uaring up being performed by a buffer gate 87.
The function of this delay and gating circuitry is to provide, at the output of gate 85, a brief pulse for each transition, posi-tive or negative, in ~he input signal A. A completely similar circuit provides, in re~ponse to the input signal B, a corresponding pulse train at the output of an exclusive OR gate 89. The pulse trains obtained from the gates 85 and 89 are com-bined in an exclusive OR gate 91. The output of this gate comprises a pulse for each transition in either of the input signals (A or B). In effec~, a factor of four multiplication in 1 17037~
1 the pulse rate is provided as compared with the pulse rate of either one of the input signals. If the carriage were driven by a stepper motor instead of the d.c. servomotor 27, the pulse signal used to advance that motor might be used in place of the pulse train generated by the shaft encoder 37.
The pulse train obtained from the gate 91 is applied to a counter 101 so that the counter generates a digital value which varies in proportion to displacement of the carriage. This counter 101 is reset along with the resetting of the integrators 71 and 73 at the start of each character. Thus, the digital value held by the counter in one sense represents displacement across the character position. The digital value in counter 101 is converted to an analog signal voltage by a digital to an~log (D/A) converter 103, the transfer being buffered by a latch 105 which is loaded in synchronism with the counting to minimize ripple-through effects. In one sense, the output voltage from the D/A converter 103 comprises a ramp as the carriage moves across the platen. This ramp voltage, however, is not a time dependent function in the usual sense, but rather is proportional to actual displacement of the carriage and thus, in the time domain, will vary as the speed of the carriage varies.
The rarnp voltage obtained from D/A converter 103 is mixed in or summed with the X axis position signal obtained from the integrator 73, the ramp ignal being applied, through a resistor R9, to a summing junction S at the input of error amplifier 77. The addition of this carriage displacement com-ponent into the vector-defining voltage allows the writing of characters from the moving carriage without requiring alteration 1 of the basic vector encoding scheme and, in a manner, allowing the velocity of the carriage to change. Because of this compen-sation, the carriage can be driven re~atively rapidly when simple characters are being written and more slowly for more complex characters. In this way, the throughput of the machine can be substantially increased as compared with the situation which would exist if the speed of the carriage had to be kept constant, as would be the case if compensation were built into the vector encoding scheme. In such a case the single speed chosen would have to be relatively low, i.e. selected to permit forming of the most complex character to be written.
Selection of carriage speed is performed by the micro-processor system of Fig. 3, a data word representing the desired carriage speed being output through the port 52. This data, at five bits of accuracy, is applied to a digital-to-analog con-verter 111. The output signal from converter 111, which is an analog voltage representing desired speed, is compared with a voltage representing actual speed. This latter voltage is obtained by a frequency-to-voltage converter 113 driven by the pulse train from gate 91. As described previously, the pulse in this train is generated at a rate which is proportional to the speed of the carriage, being derived from the shaft encoder asso-ciated with the carriage drive motor 27. The output voltages from the frequency-to-voltage converter 113 and the ~/A converter 111 are applied, through respective mixing resistors Rll and R13, to a summing junction T to derive an error signal. This error is amplified as indicated at 117. The amplified error signal is mixed with an a.c. component obtained from a dither oscillator 1 119 at the input of an amplifier 121 which, in turn, drives a power amplifier controlling the servomotor 27.
The embodiment illustrated includes provision for forming characters of different sizes from the same font data, i.e. the digital data being applied directly to the digital-to-analog converters 61 and 63. For this purpose, the converters are of the so-called multiplying type in which the output voltage is proportional, not only to the digital value applied, but also to an analog reference voltage. A four bit data word, again obtained from the microprocessor controller of Fig. 3, is applied to a decoder 72 which generates two separate one-of-four selec-tion signals. Each of these set of signals is applied to a respective quad switch 74 and 76 to select one of four predeter-mined voltages for application, as a reference voltage, to the respective digital analog converter 61 or 63. The predetermined voltages are obtained from a voltage divider comprising resistors R21-R24. The resistors R21-R24 are selected to produce voltages corresponding to desired typesizes rather than to perform a nor-mal digital-to-analog conversion. The nature of the decoding is such that only one switch in each of the packages is on at any one time so that the reference voltage applied to each digital-to-analog converter 61 or 63 may be independently selected.
Accordingly, since the horizontal and vertical scaling factors can be selected separately, characters of different aspect ratios can be formed from the same data as well as merely scaling the characters.
In the embodiment illustrated, the axis o~ one of the linear servotransducers driving the stylus is parallel to the ~ 17037.~
1 direction of carriage movement and the other axis is essentially perpendicular thereto. Accordingly, the displacement based com-pensation signal only needs to be mixed with one of the two control signals driving the servotransducers in order to obtain the desired moving frame of reference. On the other hand, those skilled in the art will appreciate that an arrangement could be utilized in which the axes of both linear servotransducers were at an angle, e.g. 45 to the direction of carriage movement, though perpendicular to each other. In such a case, displacement compensation components of appropriate magnitude would be æummed with each of the servocontrol signals, observing appropriate polarity. Such an arrangement should be understood to be within the scope of the present invention. Similarly, it should also be understood that it is relative motion between the platen and the stylus mount which is significant and that either component might actually be moved even though movement of the stylus mount (carriage) is disclosed in the preferred embodiment.
Summarizing, it can be seen that the present invention facilitates the digital encoding of character defining vectors with respect to a seemingly fixed frame of reference. High speed writing of characters from a moving frame of reference, the carriage, is then accomplished by summing, with at least one of the writing servocontrol voltages, a compensating voltage which -- represents displacement across a character position. Thus, co~-pensation for the moving frame of reference is achieved essen-tially independently of carriage speed.
In view of the foregoing, it may be seen that several o~jects of the present invention are achieved and other advan-tageous results have been attained.
1 As various changes could be made in the above construc-tions without departing from the scope of the invention, it should be understood that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Claims (10)
1. In a calligraphic character printer in which characters are printed successively along a line, a character drawing mechanism which comprises:
a platen;
a stylus for writing against said platen;
mounting means for said stylus;
carried on said mounting means, a pair of linear transducers for moving said stylus in transverse directions thereby permitting positioning of said stylus within a predetermined region relative to the mounting means;
means for providing relative movement between said platen and said mounting means at a selectable speed and for generating a voltage which varies in proportion to the movement;
means for generating a pair of voltages which represent position components along the said transverse directions which position voltages vary to define a character relative to a fixed frame of reference;
means for summing the movement voltage with at least one of said relative position component voltages thereby to obtain respective control voltages;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
a platen;
a stylus for writing against said platen;
mounting means for said stylus;
carried on said mounting means, a pair of linear transducers for moving said stylus in transverse directions thereby permitting positioning of said stylus within a predetermined region relative to the mounting means;
means for providing relative movement between said platen and said mounting means at a selectable speed and for generating a voltage which varies in proportion to the movement;
means for generating a pair of voltages which represent position components along the said transverse directions which position voltages vary to define a character relative to a fixed frame of reference;
means for summing the movement voltage with at least one of said relative position component voltages thereby to obtain respective control voltages;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
2. In a calligraphic character printer in which characters are printed successively along a line, a character drawing mechanism which comprises:
a carriage;
a stylus supported on said carriage;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative to the carriage;
means for driving said carriage along said line at a selectable speed and for generating a voltage which varies in proportion to the displacement of the carriage;
means for generating a pair of voltages which represent position components along the said transverse directions which position voltages vary to define a character relative to a fixed frame of reference;
means for summing the carriage displacement voltage with at least one of said relative position component voltages thereby to obtain respective control voltages;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
a carriage;
a stylus supported on said carriage;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative to the carriage;
means for driving said carriage along said line at a selectable speed and for generating a voltage which varies in proportion to the displacement of the carriage;
means for generating a pair of voltages which represent position components along the said transverse directions which position voltages vary to define a character relative to a fixed frame of reference;
means for summing the carriage displacement voltage with at least one of said relative position component voltages thereby to obtain respective control voltages;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
3. A printer as set forth in claim 2 wherein the carriage displacement voltage generated by said carriage driving means is reset at the start of drawing of each character.
4. A printer as set forth in claim 2 wherein each of said transducers includes means for generating a feedback voltage and wherein said carriage displacement voltage and respective feedback and control voltages are combined at an error amplifier driving at least one of said transducers.
5. In a calligraphic character printer, a character drawing mechanism which comprises:
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage;
means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage;
means for generating a pair of voltages which represent velocity components along the said transverse directions;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for summing the carriage displacement voltage with at least one of said relative position voltages thereby to obtain respec-tive control voltages representative of position with respect to said platen;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage;
means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage;
means for generating a pair of voltages which represent velocity components along the said transverse directions;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for summing the carriage displacement voltage with at least one of said relative position voltages thereby to obtain respec-tive control voltages representative of position with respect to said platen;
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
6. A printer as set forth in claim 5 wherein the direction of stylus movement provided by one of said transducers is essentially parallel to the carriage and wherein said carriage displacement voltage is summed with the output voltage of the intergrator corresponding to that transducer.
7. A printer as set forth in claim 6 wherein the the carriage displacement voltage generated by said carriage driving means is reset at the start of drawing of each character and said integrators are reset simultaneously.
8. In a character printer in which each of a series of successive characters is represented by a plurality of digital data words, a character drawing mechanism which comprises:
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage;
means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage starting from a preselectable point corresponding with the edge of a character location on the platen;
means for generating, from said data words, a pair of voltages which represent velocity components along the said transverse direction;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for summing the carriage displacement voltage with at least one of said relative position voltages thereby to obtain respec-tive control voltages representative of stylus position with respect to said platen;
8. In a character printer in which each of a series of successive characters is represented by a plurality of digital data words, a character drawing mechanism which comprises:
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage;
means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage starting from a preselectable point corresponding with the edge of a character location on the platen;
means for generating, from said data words, a pair of voltages which represent velocity components along the said transverse direction;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for summing the carriage displacement voltage with at least one of said relative position voltages thereby to obtain respec-tive control voltages representative of stylus position with respect to said platen;
Claim 8 cont'd.
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
means for driving said transducers to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the relative position voltages essentially independent of the velocity of the carriage.
9. A printer as set forth in claim 8 wherein the direction of stylus movement provided by one of said transducers is essentially parallel to the carriage and wherein said carriage displacement voltage is summed with the output voltage of the integrator corresponding to that transducer.
10. In a character printer in which each of a series of successive characters is represented by a plurality of digital data words, a character drawing mechanism which comprises:
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage, one of said transverse directions being essentially parallel to the direction of carriage movement, each of said transducers including means providing a feedback signal means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage;
means for generating, from said data words, a pair of voltages which represent velocity components along the said transverse direction;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for combining the carriage displacement voltage with the relative position voltage corresponding to the transducer which parallels carriage movement and with the respective feedback signal thereby to obtain a respective control voltage representative of position with respect to said platen;
10. In a character printer in which each of a series of successive characters is represented by a plurality of digital data words, a character drawing mechanism which comprises:
a platen;
a carriage traversable across said platen;
carried on said carriage, a pair of linear transducers for moving said stylus in essentially transverse directions thereby per-mitting positioning of said stylus within a predetermined region relative the carriage, one of said transverse directions being essentially parallel to the direction of carriage movement, each of said transducers including means providing a feedback signal means for driving said carriage across said platen at a select-able speed and for generating a voltage which varies in propor-tion to the displacement of the carriage;
means for generating, from said data words, a pair of voltages which represent velocity components along the said transverse direction;
a pair of integrators for generating, from said velocity voltages, respective relative position voltages;
means for combining the carriage displacement voltage with the relative position voltage corresponding to the transducer which parallels carriage movement and with the respective feedback signal thereby to obtain a respective control voltage representative of position with respect to said platen;
Claim 10 cont'd.
means for combining the position and feedback signals corresponding to the transverse transducer thereby to obtain a respective control voltage;
means for resetting said carriage displacement voltage and both of said integrators at the start of drawing of each character;
means for driving each said transducers in response to the respective control voltage to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the rela-tive position voltages essentially independent of the velocity of the carriage.
means for combining the position and feedback signals corresponding to the transverse transducer thereby to obtain a respective control voltage;
means for resetting said carriage displacement voltage and both of said integrators at the start of drawing of each character;
means for driving each said transducers in response to the respective control voltage to effect stylus movement which is, relative to the carriage, proportional to said control voltages and which is, relative to the platen, proportional to the rela-tive position voltages essentially independent of the velocity of the carriage.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24266381A | 1981-03-11 | 1981-03-11 | |
| US242,663 | 1981-03-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1170374A true CA1170374A (en) | 1984-07-03 |
Family
ID=22915697
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398069A Expired CA1170374A (en) | 1981-03-11 | 1982-03-11 | High speed character writer |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS57201659A (en) |
| BE (1) | BE892442A (en) |
| BR (1) | BR8201295A (en) |
| CA (1) | CA1170374A (en) |
| DE (1) | DE3208793A1 (en) |
| FR (1) | FR2501593B1 (en) |
| GB (1) | GB2094998B (en) |
| IT (1) | IT1155129B (en) |
| MX (1) | MX152471A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2792574B1 (en) * | 1999-04-23 | 2001-07-27 | Signascript | WRITING REPRODUCTION MACHINE |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3524978A (en) * | 1966-09-09 | 1970-08-18 | Hitachi Ltd | Curve-plotting system with interpolation |
| JPS5315465B2 (en) * | 1973-03-09 | 1978-05-25 | ||
| GB1493803A (en) * | 1973-11-28 | 1977-11-30 | Moffatt R | Writing apparatus |
| US4150902A (en) * | 1976-07-19 | 1979-04-24 | Ing. C. Olivetti & C. | Electronic printer having a single tracing element for tracing out alphanumeric characters |
-
1982
- 1982-03-05 GB GB8206547A patent/GB2094998B/en not_active Expired
- 1982-03-10 IT IT67300/82A patent/IT1155129B/en active
- 1982-03-10 BE BE0/207527A patent/BE892442A/en not_active IP Right Cessation
- 1982-03-10 FR FR8204055A patent/FR2501593B1/en not_active Expired
- 1982-03-10 BR BR8201295A patent/BR8201295A/en unknown
- 1982-03-11 DE DE19823208793 patent/DE3208793A1/en not_active Withdrawn
- 1982-03-11 MX MX191767A patent/MX152471A/en unknown
- 1982-03-11 CA CA000398069A patent/CA1170374A/en not_active Expired
- 1982-03-11 JP JP57039257A patent/JPS57201659A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| MX152471A (en) | 1985-07-25 |
| IT8267300A0 (en) | 1982-03-10 |
| GB2094998A (en) | 1982-09-22 |
| FR2501593B1 (en) | 1986-01-17 |
| GB2094998B (en) | 1985-01-16 |
| DE3208793A1 (en) | 1982-09-23 |
| IT1155129B (en) | 1987-01-21 |
| BR8201295A (en) | 1983-01-25 |
| FR2501593A1 (en) | 1982-09-17 |
| BE892442A (en) | 1982-07-01 |
| JPS57201659A (en) | 1982-12-10 |
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