Method of and apparatus for printing colored patterns

A method of printing dots of at least two different colors including first and second colors on a record sheet with use of a printing head having a multiplicity of heater elements which are arranged in an array extending along a substantially straight print line and which are operative to produce heat independently of one another when actuated and an elongated heat-sensitive ink ribbon extending between the record sheet and the array of said heater elements and having a series of recurrent colored sections which are contiguous to one another and which are inked in said colors, said heater elements comprising a succession of groups each having a predetermined number of successive subgroups each consisting of a predetermined number of heater elements and forming a zone having a predetermined length, the colored sections of said first and second colors occurring, lengthwise of the ribbon, successively and recurrently with a unit series including one colored section of the first color and one colored section of the second color, all the colored sections of the ink ribbon having a predetermined length, the method having a succession of line forming cycles each for forming a single line of dots in at least one of said different colors on the record sheet, each of the line forming cycles consisting of a predetermined number of dot printing steps each comprising

• driving the record sheet to advance a predetermined distance across said print line in a direction substantially perpendicular to the print line during each of said line forming cycles;
• driving said ink ribbon to travel a predetermined distance with respect to said printing head in a predetermined direction angled to the direction of travel of the record sheet during each dot printing step, said predetermined distance of travel of the ink ribbon being substantially equal to said predetermined length of said zone and being smaller than said predetermined length of said colored sections of the ink ribbon;
• on the basis of control signals supplied from an external source, selecting out of said heater elements of the printing head the heater elements to be actuated to generate heat during each dot printing step;
• and
• actuating the selected heater elements for producing dots of at least one of said colors on said ink ribbon during each dot printing step,
• wherein the heater elements to be actuated to generate heat during each dot printing step are selected by selecting one of the subgroups of each of said groups and selecting particular heater elements out of the heater elements of the non-selected subgroups during each dot printing step, and wherein said predetermined distance of travel of the ink ribbon is selected so that every adjacent two of the colored sections of the ink ribbon have trailing and leading marginal areas, respectively, which are located substantially in registry with the selected one of said subgroups during each dot printing step.