Method and apparatus for driving and controlling an improved solenoid impact printer

• US 5,204,802 A
• Filed: 08/19/1991
• Issued: 04/20/1993
• Est. Priority Date: 11/23/1988
• Status: Expired due to Term

• Current Assignee: Datacard Corp. (Entrust Corp.)
• Original Assignee: Datacard Corp. (Entrust Corp.)
• Inventors: Howes, Ronald B. Jr., Emmons, Thomas R., Warwick, Dennis J.
• Primary Examiner(s): Gaffin, Jeffrey A.
• Application Number:
  US07/749,625
• Time in Patent Office: 610 Days
• Field of Search: 323/282, 323/285, 323/287, 361/152, 361/153, 361/154, 361/160
• US Class Current: 361/154
• CPC Class Codes: B41J 3/38 for embossing, e.g. for making matrices for stereotypes
• CPC Class Codes: B44B 5/0061 characterised by the power drive
• CPC Class Codes: H01H 47/325 by switching regulator

Abstract

A method and apparatus for a two-pulse solenoid embossing system implementing an amplitude feedback circuit, i.e., current monitor (48), to provide precise amplitude and timing control over two current pulses (4, 5), and thereby provide precision control over the position and velocity of the embossing system'"'"'s print elements (64a, 64b). To maintain the current amplitude during the second current pulse (5), the method and apparatus alternatively switches the power on and off to the solenoid coils (55) with a frequency such that a substantially constant current amplitude is maintained in the solenoid coils (55). The embossing system provides an improved solenoid body assembly (61) including a first stack of steel laminations (93), a center block (82) and a second stack of steel laminations (81). A plunger (62) is slidably connected to the solenoid body assembly (61) by shaft (63). Cavities (79) receive dowel pins (71) which are attached to plunger (62). The cavity and dowel pin arrangement (79, 71) prevents the plunger (62) from rotating.

Claims

1. An apparatus for controlling an impact imprinting system of a type including print elements used to imprint a chosen material, comprising:

a) solenoid means for driving the print elements in response to a current pulse;

b) current pulse generator means electrically interconnected to the solenoid means for generating and transmitting first and second current pulses to said solenoid means, said first current pulse having a contact duration and a contact amplitude sufficient to actuate said solenoid means to cause the print elements to move to a position proximate the chosen material, said second current pulse having an imprint duration and an imprint pulse amplitude sufficient to actuate said solenoid means to cause the print elements to imprint the chosen material to a desired character height;

c) current monitor means electrically interconnected to the current pulse generator means for sensing amplitude of said first and second current pulses and for transmitting first and second current amplitude sense signals representative of said amplitude of said first and second current pulses, respectively, and

d) current pulse control means electrically interconnected to said current pulse generator means and said current monitor means for switching said current pulse generator means between a pulse generating state and a nonpulse generating state, said current pulse control means including a first signal control means for comparing said first current amplitude sense signal received from said current monitor means to a first predetermined amplitude value corresponding to said contact pulse amplitude and, upon detection of said first predetermined amplitude value, switching said current pulse generator to said nonpulse generating state after a first predetermined period of time, corresponding to said contact pulse duration, said current pulse control means including a second signal control means for comparing said second current amplitude sense signal received from said current monitor means to a second predetermined amplitude value corresponding to said imprint pulse amplitude and, upon detection of the second amplitude value, switching said current pulse generator to said nonpulse generating state after a second predetermined period of time, corresponding to said imprint pulse duration.

2. The apparatus in claim 1 wherein said current pulse generator means comprises a first current pulse generator means for generating said first current pulse and a second current pulse generator means for generating said second current pulse.

3. The apparatus of claim 1 wherein said current pulse generator means includes a tri-state operation means for selectively generating a first current signal which steeply increases in amplitude over time, a second current signal which gradually decreases in amplitude over time or a third current signal which steeply decreases in amplitude over time.

4. The apparatus of claim 1 wherein said current pulse generator means includes an alternating switch means for generating a current signal which remains substantially constant in amplitude over time.

5. The apparatus of claim 4 wherein the current pulse generator means further includes a tri-state operation means for selectively generating a first current signal which steeply increases in amplitude over time, a second current signal which gradually decreases in amplitude over time or a third current signal which steeply decreases in amplitude over time, said alternating switch means being accomplished by alternating between generating said first current signal and said second current signal with a frequency such that said current signal remains substantially constant in amplitude over time.

6. The apparatus of claim 1 wherein said current pulse generator means comprises:

(a) an upper switch electrically interconnected to said current pulse control means for receiving control signals from said current pulse control means to switch said upper switch on or off such that when said upper switch is on, said upper switch is electrically connected in series with a power supply means and an upper connector of said solenoid means;

(b) lower switch electrically interconnected to said current pulse control means for receiving said control signals from said current pulse control means to switch said lower switch on or off such that when said lower switch is on, said upper switch is electrically connected in series with a lower connector of said solenoid means and said current monitor means such that when said upper and lower switches are on, a current will flow from said power supply means, through said upper switch, through said solenoid means, through said lower switch and through said current monitor means;

(c) a first diode electrically connected to said solenoid means and power supply means such that when said upper switch is one and said lower switch is off, said current will flow from said power supply means, through said solenoid means, through said first diode and back to said means for supplying the power; and

(d) a second diode electrically connected to ground, to said upper switch and to said solenoid means such that when said upper and lower switches are off a current path is formed from said second diode, through said solenoid means, through said first diode and through said power supply means.

7. The apparatus of claim 6 wherein said upper and lower switches are upper and lower transistors respectively, said upper transistors having a collector, a base and an emitter and said lower transistor having a collector, a base and an emitter, said upper and lower transistor bases being electrically connected to said control means for receiving said control signals from said control means, said upper transistor collector being electrically connected to said power supply means, said upper transistor emitter being electrically connected to said upper connector of said solenoid means, said lower transistor collector being electrically connected to said lower connector of said solenoid means, and said lower transistor emitter being electrically connected to said current monitor means.

8. The apparatus of claim 1 wherein said current monitor means comprises a sense resistor where said first and second current amplitude sense signals are derived from measuring a voltage drop across said sense resistor.

9. The apparatus of claim 8 wherein said processing means is an integration means for integrating said first and second current amplitude sense signals a first time to obtain velocity information about the print elements and for integrating said first and second current amplitude sense signals a second time to obtain said position information about the print elements.

10. The apparatus of claim 1 wherein said current control means comprises:

(a) main control means for storing and transmitting amplitude information corresponding to said first and second predetermined amplitude values and for storing and transmitting durational information corresponding to said first and second predetermined periods of time;

(b) a switch control means electrically interconnected to said main control means and to said current pulse generator means, where said switch control means receives said amplitude and durational information from said main control means; and

c) amplitude control means electrically interconnected to said current monitor means for receiving said first and second current amplitude sense signals, said amplitude control means also being electrically interconnected to said switch control means, where said switch control means transmits said amplitude information to said amplitude control means for comparison to said first and second current amplitude sense signals and, upon detection of said first and second predetermined amplitude values, said amplitude control means transmits a trigger to said switch control means, and in response to said trigger and said durational informational information, said switch control means transmits control signals in a proper time sequence to said current generator means such that said current generator means generates said first and second current pulses.

11. The apparatus of claim 10 wherein said amplitude control means further includes a safety means for avoiding current overload in said current generator means such that when said first or second current amplitude sense signals equals or exceeds a current overload limit, said amplitude control means transmits a second trigger to said switch control means, and in response to said second trigger, said switch control means switches said current generator means into said nonpulse generating state.

12. The apparatus of claim 10 wherein said current pulse control means further comprises a power line monitor means for monitoring power supply means and for transmitting a warning signal to said main control means when power is insufficient or is being turned off, and in response, said main control disengages said current pulse generator means.

13. The apparatus of claim 1 wherein said current pulse control means further includes a system failure means for disengaging said current generator means when said current generator means fails to respond to control signals transmitted from said current pulse control.

14. The apparatus of claim 1 wherein said control means includes a processing means for processing said first and second current amplitude sense signals to provide velocity and position information about the print elements.

15. A method of imprinting using an imprinting system including print elements used to imprint a chosen material and solenoid means including a solenoid coil, said method comprising:

(a) applying to said solenoid coil a first current signal which steeply increases in amplitude over time;

(b) while applying said first current signal, sensing current amplitude in the solenoid coil to obtain a sensed current amplitude signal;

(c) comparing said sensed current amplitude signal with a predetermined current amplitude value to determine when said predetermined amplitude value is obtained;

(d) after said predetermined current value is obtained, applying to said solenoid coil a second current signal which gradually decreases over time for a predetermined duration so as to move a print element to a surface of the chosen material;

(e) then applying to said solenoid coil a third current signal which steeply decreases over time until said current amplitude is substantially zero; and

(f) then forcing the print element into the chosen material thereby deforming the chosen material.

16. A method of imprinting using an imprinting system including print elements used to imprint a chosen material and solenoid means including a solenoid coil, said method comprising:

(a) moving a print element to a surface of the chosen material to be imprinted;

(b) applying to said solenoid coil a first current signal which steeply increases in amplitude over time;

(c) while applying said first current signal, sensing current amplitude in the solenoid coil to obtain a sensed current amplitude signal;

(d) comparing said sensed current amplitude signal with a predetermined current amplitude value to determine when said predetermined current amplitude value is obtained;

(e) after said predetermined current amplitude value is obtained, alternating between applying to said solenoid coil said first current signal and a second current signal which gradually decreases over time with a frequency such that a substantially constant current amplitude, equal to said predetermined amplitude value, is maintained for a predetermined duration so as to force the print element into the chosen material thereby deforming the chosen material; and

(f) then applying to said solenoid coil a third current signal which steeply decreases over time until current amplitude is substantially zero.