US3900095A - Driving circuits for electrical printers - Google Patents

Driving circuits for electrical printers Download PDF

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Publication number
US3900095A
US3900095A US365589A US36558973A US3900095A US 3900095 A US3900095 A US 3900095A US 365589 A US365589 A US 365589A US 36558973 A US36558973 A US 36558973A US 3900095 A US3900095 A US 3900095A
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United States
Prior art keywords
driving
solenoid
circuit
pulse
terminal
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Expired - Lifetime
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US365589A
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English (en)
Inventor
Koji Tanabe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Citizen Watch Co Ltd
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Citizen Watch Co Ltd
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    • 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
    • B41J9/00—Hammer-impression mechanisms
    • B41J9/44—Control for hammer-impression mechanisms

Definitions

  • My invention relates to a driving circuit for use in electrical printers and more particularly to a driving circuit which is capable of being operated by a control pulse and can excite a solenoid for operating a mechanical print driving-member, for example, a print drivinghammer etc. with the aid of an exciting pulse produced across a condenser.
  • the driving circuit according to my invention is particularly useful for the hammer-driving type or needle-dot type electrical printer in which the solenoid for operating the mechanical pring drivingmember is energized by an exciting pulse produced from a condenser.
  • the exciting pulse applied to the solenoid has a voltage waveform which is uniform in level.
  • An application of an exciting pulse having a voltage waveform of uneven level may result in a change of the electromagnetic force produced by the solenoid, thereby changing the mechanical force urged against the print-driving member and hence changing the printing speed. As a result, the printing characteristics of the electrical printer may become degraded.
  • An object of my invention is to provide a driving circuit which can obviate disadvantages encountered by the conventional driving-circuits heretofore and described in further detail in conjunction with the specific description of my improved driving circuit; which is simple in construction and reliable in operation and hence is particularly useful for electrical printers.
  • Another object of my invention is to provide a driving circuit which is not influenced by any voltage variation across a current supply-circuit and hence does not require any special current supplycircuit.
  • a further object of my invention is to provide a driving circuit which is capable of using a current supplycircuit having a small current-carrying capacity and obtaining significantly good printing characteristics.
  • My invention provides a driving circuit for use in electrical printers comprising a control-pulse supplycircuit, at least one driving transistor whose base is connected to the control-pulse supply-circuit, a solenoid connected to the emitter of the driving transistor and adapted to operate a mechanical print driving-member when energizing, a condenser connected between the collector of the driving transistor and the solenoid for generating an exciting pulse for energizing the solenoid, and a current supply-circuit connected in parallel with the condenser, the terminal voltage of the condenser being kept at a voltage higher than the voltage of the exciting pulse.
  • FIG. 1 is a schematic circuit diagram of a conventional driving circuit for use in electrical printers
  • FIG. 2a shows a voltage wave-form diagram of a conventional driving circuit shown in FIG. 1 for illustrating a varying exciting pulse voltage-level
  • FIG. 2b shows a voltage wave form diagram of a driving circuit for use in electrical printers according to my invention for illustrating a uniform exciting-pulse voltage level
  • FIG. 3 is a schematic circuit diagram of a first embodiment of a driving circuit for use in electrical printers according to my invention
  • FIG. 4 is a schematic circuit diagram of a second embodiment of a driving circuit for use in electrical printers according to my invention.
  • FIG. 5 is a schematic circuit diagram of a third embodiment of a driving circuit for use in electrical printers according to my invention.
  • a conventional driving circuit of prior art for use in electrical printers as shown in FIG. 1 includes a driving transistor 1 whose collector electrode is connected to one end of a solenoid 2, the other end of which is connected through an electric current supply circuit 3 to the emitter electrode of driving transistor 1. Across the base and emitter electrodes of driving transistor 1 is applied a control pulse 4 to make driving transistor 1 conductive. Thus, a current amplification of the control pulse 4 is effected by means of driving transistor 1.
  • the solenoid 2 is energized by an exciting pulse suppled from the electric current supply source 3 to operate, for example, a driving hammer (not shown) such that the driving hammer is urged against a print wheel (not shown), thereby completing a desired printing operation.
  • a conventional driving circuit uses a driving transistor 1 whose collector is connected to the solenoid 2 so that the driving circuit cannot be applied to the electrical printer to operate it reliably. That is, in the conventional driving circuit shown in FIG. 1 the control pulse 4 merely serves to make driving transistor 1 conductive while the exciting pulse supplied to solenoid 2 is controlled by the characteristics of the electric current supply circuit 3. As a result, a variation in voltage of the electric current supply circuit 3 directly results in a voltage wave variation of the exciting pulse applied to solenoid 2 thereby degrading the characteristics of the electric printer. In order to obviate such a disadvantage, certain special precautions must be taken for stabilizing the electric current supply circuit 3, rendering, the apparatus as a whole large in size and expensive. In electrical printers, a plurality of solenoids 2 must simultaneously be excited for the purpose of printing a plurality of figures, and as a result, a special electric current supply circuit 3 having a large current capacity is required.
  • FIG. 2a shows the variation of exciting pulse voltage V; across the condenser 3 as a function of time 2 for the above mentioned conventional driving circuit for use in electrical printers.
  • a control pulse 4 is applied to the base of driving transistor 1 to make transistor 1 conductive.
  • the terminal voltage V across the condenser is applied to solenoid 2.
  • the con denser is discharged up to a time to produce an exciting pulse which is substantially triangular in shape as shown in FIGf2a depending on the discharging characteristics of the condenser and its associated circuit. From t at which time control pulse 4 ceases condenser 3 is charged again until time t as shown by a dotted line. From time t;, at which time control pule 4 reappears, condenser 3 is again discharged up to time t.,
  • the ingcircuit provides exciting pulse voltages whose waveformsaredetermined by the discharging characteristics of the condenser and its associated circuit. If the time constant of the discharging circuit is small, the waveform of the exciting pulse voltage becomes substantially triangular in shape as shown in FIG. 2a. Such a triangular voltage waveform of the exciting pulse cannot produce a driving force which can operate the electrical printer reliably.
  • solenoid 2 is energized after a short interval of time following 1 for example, at t as shown in FIG. 2a, it is impossible to charge the condenser sufficiently, and as a result, only a low terminal voltage V of the condenser shown in FIG. 2a is supplied to solenoid 2, the driving potential getting correspondingly decreased.
  • FIG. 3 a first embodiment of my invention in which P P P -designate a plurality of driving circuits which are identical in construction and correspond to respective characters of an electrical printer.
  • Each driving circuit comprises first and second driving transistors 5 and 6 respectively of substantially similar characteristics and connected in the conventional, Darlington fashion, elements of the second and third driving circuits shown being denoted by respective suffixes out e.g. 5 and 5".
  • a control signal 7 from a control pulse supply circuit 7' is supplied to the base of the first driving transistor 5.
  • a conventional electric current-supply circuit consists of a stepdown transformer 10 for lowering the voltage of a conventional alternating frequency electricsupply source and of a full'wave rectifier circuit 11.
  • the output terminals of full wave rectifier circuit 11 are connected in parallel with a condenseer 12 and with the above mentioned driving circuits P P through P
  • the driving circuit shown in FIG. 3 operates as follows.
  • the first and second driving transistors 5 and 6 associated with a character of the printer are non-conductive; at this time condenser 12 is sufficiently charged from electric current supply source S.
  • the period of time for charging condenser 12 is determined by the time constant of the charging circuit, and a resistor may be added for suitably increasing that time constant.
  • the charging time for condenser 12 may be suitably determined as a function of the space between successive character print-outs of the electrical printer. Thus, it is possible to determine the optimum charging time of condenser 12 for the highest printing speed.
  • both first and second driving transistors 5 and 6 become conductive to complete a conductive path from condenser 12 through second driving transistor 6 to solenoid 8.
  • This allows a discharge current from charged condenser 12 to be supplied to solenoid 8 energizing the latter, and as a re--' sult, energized solenoid 8 urges a driving hammer (not shown) against a print wheel (not shown) or projects a print needle onto a print completing a desired character imprint.
  • both first and second driving transistors 5 and 6 are nonconductive and solenoid 8 is deenergized.
  • a counter electromotiveforce produced at this instant as a result of cessation of current through solenoid 8 is eliminated by a diode 9 in the well known manner.
  • condenser 12 At time t condenser 12 is charged to a saturation terminal voltage V and if control pulse 7 is applied to the base of the first driving transistor 5 the exciting pulse-voltage V is applied to solenoid 8.
  • solenoid 8 is connected to the emitter of the second driving transistor 6 so that the saturation terminal-voltage V of condenser 12 is not applied directly to solenoid 8.
  • the exciting pulse voltage V applied to solenoid 8 is substantially determined by control pulse 7, i.e., the value and waveform of the exciting pulse voltage V., are a function of control pulse 7.
  • the terminal voltage of the condenser 12 decreases to V but the same exciting pulse voltage V, is maintained during the period from time t to t across solenoid 8 thereby exciting the latter with a voltage pulse of uniform level.
  • control pulse 7 is not applied to the base of the first driving transistor 5 during the time period to condenser 12 is again charged from electric-current supply source S to a terminal voltage V as shown by a dotted line. If at time t the control pulse 7 is applied to the base of the first driving-transistor 5, solenoid 8 is again energized for the time period t to t., the above sequence of events being thereby repeated.
  • a resistor 13 is connected between the base of the first driving transistor 5 and in lieu of solenoid 8 diode 9 shown in FIG. 3.
  • resistor 13 considerably reduces the electromotive-force produced in solenoid 8. That is, if the counter electromotive force is produced in solenoid 8 to decrease the emitter voltage of the second driving transistor 6, a weak current flows from solenoid 8 through resistor 13 first and second driving transistors 5 and 6 reentering second driving transistor 6 conductive. As a result, so-
  • this embodiment is substantially capable of rapidly and reliably eliminating a counter electromotive-force original in within solenoid 8.
  • resistor 13 may be used as a load resistor for such an emitter-follower transistor.
  • FIG. 5 shows a third embodiment of the driving circuit according to my invention in which each control pulse 7 is first amplified by a preamplifier circuit 14 and then supplied to a clamping circuit 15 whose output is applied to the base of each driving transistor 5 of respective driving circuits P. of each driving transistor 5 and energized by the exciting pulse in the same manner as explained with reference to the first and second embodiments of my invention.
  • the voltage level V. of the exciting pulse may be adjusted by merely changing the level of clamping circuit 15, by, for example altering the value of resistor and so controlling the maximum positive voltage fed and for example, to the base of transistor 5, whereby the print can be operated in a reliable fashion.
  • the driving circuit for use in electrical printers has a number of advantages.
  • a solenoid is connected to an emitter of a driving transistor and is energized by a discharge current from a condenser so that it is possible to make the voltage level of the exciting pulse independent of the voltage variation in an electric current supply-circuit.
  • the voltage level of the exciting pulse is always uniform so that the printing characteristics of electrical printers and more particularly of a high speed electrical printer may be improved.
  • a control pulse is generated from an integrated circuit etc.
  • the solenoid may be energized by an exciting pulse whose voltage level is correspondingly uniform.
  • a special current supplycircuit is not required and hence use may be made of a current supply-circuit having a relatively small current-carrying capacity.
  • electromotive force produced in the solenoid may be substantially eliminated in a simple and reliable manner.
  • a driving circuit for an electrical printer comprising:
  • At least one driving transistor having an emitter electrode, a collector electrode and a base electrode, said base electrode being connected to said control-pulse supply circuit;
  • a solenoid having one terminal connected to the emitter electrode of said driving transistor and adapted to operate a mechanical print-driving member
  • a capacitor connected directly to the collector electrode of said driving transistor and between said collector electrode and another terminal of said solenoid for generating an exciting pulse for energizing said solenoid and operating said mechanical print-driving member; current-supply circuit shunted across said capacitor, the terminalvoltage of said capacitor being at a voltage higher than that of said exciting pulse;
  • a two-terminal shunting element having a first terminal connected to said other terminal of said solenoid, and a second terminal element returned to said driving transistor for eliminating a counterelectromotive force produced in said solenoid upon de-energization thereof by cessation of said exciting pulse.
  • a driving circuit as defined in claim 1 wherein a plurality of driving circuits corresponding to respective characters of an electrical printer are connected in parallel with said capacitor and said current-supply circuit, a control pulse being supplied to the base of the driving transistor of each respective driving circuit.
  • control-pulse supply circuit comprises:
  • a preamplifier circuit amplifying said control pulse and having an output applied to the base of said driving transistor of said driving circuit
  • a clamping circuit for maintaining substantially constant the level of said exciting pulse.

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  • Dot-Matrix Printers And Others (AREA)
US365589A 1972-06-06 1973-05-31 Driving circuits for electrical printers Expired - Lifetime US3900095A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1972066539U JPS4925325U (enrdf_load_stackoverflow) 1972-06-06 1972-06-06

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US3900095A true US3900095A (en) 1975-08-19

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JP (1) JPS4925325U (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4396304A (en) * 1981-11-24 1983-08-02 International Computers Limited Print head and drive circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60204556A (ja) * 1984-03-29 1985-10-16 Sato :Kk ラベルプリンタ−における巻取カセツトの装填、巻取機構

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3302070A (en) * 1965-10-22 1967-01-31 Johnson Service Co Staging network
US3432844A (en) * 1965-04-21 1969-03-11 Teletype Corp Character generation logic
US3624661A (en) * 1969-05-14 1971-11-30 Honeywell Inc Electrographic printing system with plural staggered electrode rows
US3638197A (en) * 1968-12-31 1972-01-25 Texas Instruments Inc Electronic printing input-output station
US3705333A (en) * 1972-02-09 1972-12-05 Ibm Adjustable active clamp circuit for high speed solenoid operation
US3752288A (en) * 1971-02-18 1973-08-14 Olivetti & Co Spa Electrographic printer with plural oscillating print head
US3770092A (en) * 1972-02-14 1973-11-06 Autotronics Inc Wire print head

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4312026Y1 (enrdf_load_stackoverflow) * 1966-07-21 1968-05-24

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3432844A (en) * 1965-04-21 1969-03-11 Teletype Corp Character generation logic
US3302070A (en) * 1965-10-22 1967-01-31 Johnson Service Co Staging network
US3638197A (en) * 1968-12-31 1972-01-25 Texas Instruments Inc Electronic printing input-output station
US3624661A (en) * 1969-05-14 1971-11-30 Honeywell Inc Electrographic printing system with plural staggered electrode rows
US3752288A (en) * 1971-02-18 1973-08-14 Olivetti & Co Spa Electrographic printer with plural oscillating print head
US3705333A (en) * 1972-02-09 1972-12-05 Ibm Adjustable active clamp circuit for high speed solenoid operation
US3770092A (en) * 1972-02-14 1973-11-06 Autotronics Inc Wire print head

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4396304A (en) * 1981-11-24 1983-08-02 International Computers Limited Print head and drive circuit

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JPS4925325U (enrdf_load_stackoverflow) 1974-03-04

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