US 3,941,230 A · Backlash compensated linear drive method for lead screw-driven printer carriage

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.

Claims11

Dependent claims

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.

4 more elements

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.

3 more elements

Dependencies are inferred from the claim text.

Backlash compensated linear drive method for lead screw-driven printer carriage

Life of this patent

Backlash compensated linear drive method for lead screw-driven printer carriage

Life of this patent

Abstract

Claims11