Print head carriage homing system

Claim 1

A print head carriage drive system for a printer having a frame, a print head, and an electronic printer controller, said system comprising a stepper motor, a print head carriage carrying the print head and adapted to move the print head in transverse manner for bi-directional printing operations, an endless toothed belt coupled to said stepper motor and secured to said print head carriage to move said carriage in said transverse manner, a timing strip having slots therein between portions of the strip and secured to and formed integral with the frame of the printer so as to be rigidly positioned relative to the print head carriage, and an optical sensor secured to the print head carriage and positioned to straddle the timing strip and to output signals upon sensing of the strip portions and the slots for indicating motion of the print head carriage, the sensing of a strip portion producing a high level output signal and the sensing of a slot producing a low level signal, said printer controller receiving said output signals for moving the carriage in a predetermined direction and sensing said strip portions and said slots in a pattern of high-to-low transition periods at timed intervals and sensing a high level signal for a time greater than one high-to-low transition period for establishing a tentative home position of the carriage, said printer controller moving the carriage in the opposite direction and sensing a like pattern of high-to-low transition periods at the same timed intervals for determining home position of the carriage dependent upon the times of sensing a pattern of transition periods, and then said printer controller again moving said carriage in said predetermined direction and sensing a pattern of high-to-low transition periods at the same timed intervals and sensing a high level signal for a time greater than one high-to-low transition period for verifying said home position of said carriage, and for determining a jam condition indicating non-motion of the carriage when a time greater than one high-to-low transition period expires without at least one high-to-low transition.

Claim 14

A method for determining home position of a stepper motor driven carriage for a print head on a printer having a printer controller, comprising the steps of: providing a timing strip having a plurality of slots therein between portions of the strip in an arrangement wherein the timing strip is rigidly positioned relative to the carriage; sensing the slots in the timing strip during movement of the carriage in one predetermined transverse direction and providing output signals corresponding to sensed portions and slots in a pattern of high-to-low transition periods at timed intervals and sensing a high level signal for a time greater than one high-to-low transition period for establishing a tentative home position of the carriage, sensing the portions and slots in the timing strip during movement of the carriage in the opposite transverse direction and providing output signals in a pattern of high-to-low transition periods at like timed intervals; conditioning the output signals to timing periods of repeated patterns of high-to-low transitions; and again moving said carriage in the predetermined direction and sensing a pattern of high-to-low transition periods at the same timed intervals and verifying the home position of the carriage and then stopping movement of the carriage upon observing a final high-to-low transition period greater than one transition period at the home position of the carriage.

Claim 15

A method for determining home position of a stepper motor driven carriage for a print head on a printer having a printer controller, comprising the steps of: providing a timing strip having a plurality of slots therein between portions of the strip in an arrangement wherein the timing strip is rigidly positioned relative to the carriage; sensing the slots in the timing strip during movement of the carriage in one predetermined transverse direction and providing output signals corresponding to sensed portions and slots in a pattern of high-to-low transition periods at timed intervals and sensing a high level signal for a time greater than one high-to-low transition period for establishing a tentative home position of the carriage, sensing the portions and slots in the timing strip during movement of the carriage in the opposite transverse direction and providing output signals in a pattern of high-to-low transition periods at like timed intervals; conditioning the output signals to timing periods of repeated patterns of high-to-low transitions; and again moving said carriage in the predetermined direction and sensing a pattern of high-to-low transition periods at the same timed intervals and verifying the home position of the carriage and then stopping movement of the carriage upon observing a final high-to-low transition period greater than one transition period at the home position of the carriage.