US4305080A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compensating driver circuit for thermal print head
Assignee: International Business Machines Corp
•
Filing: 1979-07-18
•
Granted: 1981-12-08
•
Expires: 1999-07-18
Abstract
Abstract A driver circuit for a thermal printing element varies the power applied to the element, depending upon its recent history of energization, in order to maintain uniform print density desprite temperature variation in the element. A capacitor charges and discharges to measure time intervals since the last element energization to control the voltage applied by an output transistor.
Inventors
- 👤 Earl A. Cunningham
- 👤 David E. Cutshall
- 👤 Gerald M. Heiling
- 👤 Ronald L. Soderstrom
- 👤 James M. Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:39
CPC Classifications
B; B41; B41J; B41J2/00; B41J2/315; B41J2/32; B41J2/35; B41J2/355; B41J2/3555; B41J2/36; B41J2/365
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
185 words
In a thermal printer having a number of individual print elements controlled by respective input signals, a corresponding number of drivers for applying power from a common power source to said print elements in response to said input signals, each of said drivers comprising: input means for receiving one of said input signals; output means responsive to said input means for coupling said common power source to one of said print elements; and tracking means coupled to said input means for measuring time intervals associated with previous ones of said input signals, and for controlling said output means in accordance with said time intervals, each of said intervals being greater than the duration of one of said input signals, wherein said tracking means includes a capacitor connected to said power source so as to charge toward first and second voltages in response to first and second input-signal levels, respectively, and wherein said output means includes a transistor coupled between said capacitor and said one print element, said transistor having a control electrode coupled to said input means for switching said transistor between conduction and cutoff.
Claim 2
Dependent Claim
185 words
In a thermal printer having a number of individual print elements controlled by respective input signals, a corresponding number of drivers for applying power from a common power source to said print elements in response to said input signals, each of said drivers comprising: input means for receiving one of said input signals; output means responsive to said input means for coupling said common power source to one of said print elements; and tracking means coupled to said input means for measuring time intervals associated with previous ones of said input signals, and for controlling said output means in accordance with said time intervals, each of said intervals being greater than the duration of one of said input signals, wherein said tracking means includes a capacitor connected to said power source so as to charge toward first and second voltages in response to first and second input-signal levels, respectively, and wherein said output means includes a transistor coupled between said capacitor and said one print element, said transistor having a control electrode coupled to said input means for switching said transistor between conduction and cutoff.
Claim 3
Dependent Claim
35 words
The thermal printer of claim 1, further including biasing means coupled from said power source to said one print element for maintaining said one print element above ambient temperature but below a printing threshold temperature.
Claim 4
Dependent Claim
39 words
The thermal printer of claim 1, wherein said tracking means includes a resistive voltage divider having a first end coupled to said power source, a tap coupled to said capacitor, and a second end coupled to said input means.
Claim 5
Dependent Claim
30 words
The thermal printer of claim 3, wherein said input means comprises a further transistor for switching said second voltage-divider end to a ground potential in response to said input signal.
References Cited (Backward Citations)
US3577137A
Cited
US3725898A
Cited
US3777116A
Cited
US4070587A
Cited
US4113391A
Cited
US4032925A
Cited
US4168421A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-12-07 | 1985-06-08 | 1985-12-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-12-07 | 1989-06-08 | 1989-12-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-12-07 | 1993-06-08 | 1993-12-08 | $7700.00 | Window Closed / Lapsed |