US3941230A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Backlash compensated linear drive method for lead screw-driven printer carriage
Assignee: AT&T Teletype Corp
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Filing: 1974-08-09
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Granted: 1976-03-02
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Expires: 1994-08-09
Abstract
Abstract A method of effecting time-linear travel of a lead screw-driven, carriage-mounted print head during the print cycle encompassed within a predetermined period of each motor-initiated advancement thereof. This is accomplished by incorporating a predetermined maximum possible amount of built-in backlash between the threaded coupling member and the lead screw, and by utilizing a predetermined time delay before printing commences so as to compensate for the backlash. The latter is employed to minimize friction and wear due selectively to any tolerance variations in the lead screw-drive nut threads, bow in the lead screw, or misalignment thereof relative to the carriage guide rods. As a result, wear of the moving parts that produce the friction is minimized. Printing of the first indicium associated with each motor-initiated advancement of the carriage is delayed until the stepping motor not only has been accelerated up to the desired rotational speed, but until the threaded member-lead screw backlash has been completely taken up, and any kinetic energy imparted carriage bounce forces resulting therefrom have been damped. As such, the carriage (and print head mounted thereon) will always be smoothly driven and at a substantially constant speed during each print cycle, so that successively printed indicia will be uniformly spaced along each print line. Before the printing of the last indicium is to take place, the motor is decelerated and stopped. Because of the inertia of the carriage and the threaded member-lead screw backlash, the carriage and the print head continue to move at the aforementioned constant speed during the printing of the last indicium.
Inventors
- 👤 Joseph A. Bellino
- 👤 Leo VON Braun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 10:25
CPC Classifications
B; B41; B41J; B41J19/00; B41J19/18; B41J19/20; B41J19/202; Y; Y10; Y10S; Y10S400/00; Y10S400/903; Y10T; Y10T74/00; Y10T74/19; Y10T74/1987; Y10T74/19893; Y10T74/19898; Y10T74/19902
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
249 words
A method of driving a carriage-mounted print head, coupled through a threaded member to a motor-driven helical lead screw, in a manner that produces time-linear carriage motion for printing uniformly spaced indicia in rapid succession during each print cycle along a given print line, including the steps of: establishing a predetermined maximum possible clearance between the threads of the threaded member and the lead screw; starting the motor preparatory to printing; delaying the printing of the first indicum not only until the motor and lead screw have been accelerated up to the desired angular rate of speed, but until the threaded member-lead screw clearance has been taken up, and any kinetic energy imparted carriage impact bounce forces resulting therefrom have been damped, at which time the carriage is then smoothly driven and at a substantially constant rate of speed by the lead screw; printing said indicia associated with each print cycle at uniformly timed intervals and with uniform spacings along each print line as a result of said carriage being driven at a constant speed during each print cycle; decelerating and stopping the motor prior to the printing of at least the last indicium associated with each print cycle preceding the stopping of the carriage; and relying on the inertial movement of the carriage and utilizing the clearance between the threaded member and the lead screw to propel the carriage and print head mounted thereon at said substantially constant speed during the printing of at least said last indicium.
Claim 2
Independent Claim
249 words
A method of driving a carriage-mounted print head, coupled through a threaded member to a motor-driven helical lead screw, in a manner that produces time-linear carriage motion for printing uniformly spaced indicia in rapid succession during each print cycle along a given print line, including the steps of: establishing a predetermined maximum possible clearance between the threads of the threaded member and the lead screw; starting the motor preparatory to printing; delaying the printing of the first indicum not only until the motor and lead screw have been accelerated up to the desired angular rate of speed, but until the threaded member-lead screw clearance has been taken up, and any kinetic energy imparted carriage impact bounce forces resulting therefrom have been damped, at which time the carriage is then smoothly driven and at a substantially constant rate of speed by the lead screw; printing said indicia associated with each print cycle at uniformly timed intervals and with uniform spacings along each print line as a result of said carriage being driven at a constant speed during each print cycle; decelerating and stopping the motor prior to the printing of at least the last indicium associated with each print cycle preceding the stopping of the carriage; and relying on the inertial movement of the carriage and utilizing the clearance between the threaded member and the lead screw to propel the carriage and print head mounted thereon at said substantially constant speed during the printing of at least said last indicium.
Claim 3
Dependent Claim
43 words
A method in accordance with claim 1 wherein the carriage and print head mounted thereon are rapidly decelerated to a stop by the previously decelerated and stopped motor after said clearance between said threaded member and said lead screw has been taken up.
Claim 4
Dependent Claim
53 words
A method in accordance with claim 2 wherein said clearance between said threaded member and said lead screw is in a range between 0.010 and 0.040 inch, and wherein the total delay between the motor is started and printing commences encompasses a period of time in a range of 6 to 18 milliseconds.
Claim 5
Independent Claim
300 words
A method of driving a carriage-mounted print head, coupled through a threaded member to a stepping motor-driven helical lead screw, in a manner that produces time-linear carriage motion for printing uniformly spaced indicia in rapid succession during each print cycle following each stepped advancement of the carriage, including the steps of: establishing a predetermined maximum possible backlash between the threads of the threaded member and the lead screw so as to minimize friction and wear due to any lead screw-drive nut tolerance variations, bow in the lead screw, and misalignment thereof relative to the path of carriage travel; starting the stepping motor preparatory to printing; delaying the printing of the first indicium associated with each stepped advancement of the carriage until the motor and lead screw not only have been accelerated up to the desired angular velocity, but until the threaded member-lead screw backlash has been taken up, and any kinetic energy imparted carriage impact bounce forces resulting therefrom have been damped, at which time the carriage is then smoothly driven at a substantially constant rate of speed by the lead screw; printing said indicia associated with each stepped advancement of the carriage at uniformly timed intervals and with uniform spacings along each print line as a result of said carriage being driven at a constant speed during each print cycle; decelerating and stopping the stepping motor prior to the printing of at least the last indicium associated with each stepped advancement of the carriage, and relying on the inertial movement of the carriage and lead screw, and on the backlash between the threaded member and the lead screw to propel the carriage and print head mounted thereon at said substantially constant speed during the printing of at least said last indicium associated with each stepped advancement of the carriage.
Claim 6
Independent Claim
300 words
A method of driving a carriage-mounted print head, coupled through a threaded member to a stepping motor-driven helical lead screw, in a manner that produces time-linear carriage motion for printing uniformly spaced indicia in rapid succession during each print cycle following each stepped advancement of the carriage, including the steps of: establishing a predetermined maximum possible backlash between the threads of the threaded member and the lead screw so as to minimize friction and wear due to any lead screw-drive nut tolerance variations, bow in the lead screw, and misalignment thereof relative to the path of carriage travel; starting the stepping motor preparatory to printing; delaying the printing of the first indicium associated with each stepped advancement of the carriage until the motor and lead screw not only have been accelerated up to the desired angular velocity, but until the threaded member-lead screw backlash has been taken up, and any kinetic energy imparted carriage impact bounce forces resulting therefrom have been damped, at which time the carriage is then smoothly driven at a substantially constant rate of speed by the lead screw; printing said indicia associated with each stepped advancement of the carriage at uniformly timed intervals and with uniform spacings along each print line as a result of said carriage being driven at a constant speed during each print cycle; decelerating and stopping the stepping motor prior to the printing of at least the last indicium associated with each stepped advancement of the carriage, and relying on the inertial movement of the carriage and lead screw, and on the backlash between the threaded member and the lead screw to propel the carriage and print head mounted thereon at said substantially constant speed during the printing of at least said last indicium associated with each stepped advancement of the carriage.
Claim 7
Dependent Claim
45 words
A method in accordance with claim 4 wherein said carriage and print head mounted thereon are rapidly decelerated to a stop by the previously decelerated and stopped motor, but only after said backlash between said threaded member and said lead screw has been taken up.
Claim 8
Dependent Claim
63 words
A method in accordance with claim 5 wherein said backlash is in a range of 0.010 and 0.030 inch, and wherein said delay before printing commences after each stepped advancement of said carriage is chosen to fall within a range commensurate with the time required to advance said carriage initially by a distance in the range of 1.2 to 2.0 times the backlash.
Claim 9
Dependent Claim
53 words
A method in accordance with claim 6 wherein during the acceleration of said carriage, energy absorbing means, mounted between said carriage and threaded member, are utilized to facilitate the damping of said carriage impact bounce forces and, thereby, shorten the delay required between when the stepping motor is started and when printing commences.
Claim 10
Dependent Claim
34 words
A method in accordance with claim 6 wherein said total delay between when the stepping motor is started and printing commences encompasses a period of time in a range of 6 to 18 milliseconds.
Claim 11
Dependent Claim
68 words
A method in accordance with claim 5 wherein said backlash is in a range between 0.010 and 0.030 inches, and wherein said additional delay required to take up any backlash and allow any impact carriage bounce forces to be dissipated after the stepping motor has accelerated said lead screw up to the desired angular velocity, and before printing commences, is in a range of 3 to 15 milliseconds.
Claim 12
Dependent Claim
80 words
A method in accordance with claim 6 wherein said stepping motor, in stopping after each stepped advancement of said carriage, with the exception of the last stepped advancement along a given print line, first reverses said lead screw and subsequently decelerated carriage by fractional amounts relative to the respective and correlated displacements required thereof to move said print head between two adjacent indicia-defining print positions within a given print cycle, before the next stepped advancement of the carriage is initiated.
Claim 13
Dependent Claim
24 words
A method in accordance with claim 10 wherein said indicia printed during each print cycle comprise uniformly spaced dots forming alphanumeric dot matrix characters.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-02 | 1979-09-01 | 1980-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-02 | 1983-09-01 | 1984-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-02 | 1987-09-01 | 1988-03-02 | $7700.00 | Window Closed / Lapsed |