Program controlled sheet folding apparatus for folding large sheets into predetermined formats

An apparatus for folding large, essentially rectangular sheets (9) by forming one or more fold lines across the sheet, comprising a folding system (5, 6, 10) for folding said sheets, a pair of driven sheet supply rollers (3) for feeding sheets in a feeding direction (B) into said folding system, said folding system including a first belt means (5) operating in a first plane, a second belt means (6) longitudinally spaced from said first belt means and operating essentially in said first plane, a third belt means (10) operating in a second plane, parallel to said first plane, spaced therefrom for defining a folding gap (14) between said planes, reversible drive means (8, 8') coupled to said belt means for driving said belt means, and control means (35) for controlling an operation of said drive means for selectively reversing a travel direction of said belt means, a first sensor (4) located upstream of said folding gap (14), as viewed in said sheet feeding direction (B) of a sheet moving from said sheet supply rollers (3) into said folding gap (14), said first sensor (4) providing a first "edge present " signal, a second sensor (16) located at a predetermined distance downstream of said first sensor (4) also as viewed in said sheet feeding direction (B), said second sensor (16) providing a second "edge present" signal, conductor means connecting said first and second sensors (4, 16) to said control means (35) for supplying said first "edge present" signal to said control means (35) to initiate an introduction of a sheet into said folding system and for supplying said second "edge present" signal to said control means (35) for initiating a drive control, said control means comprising a memory (50) having stored therein a plurality of folding programs for defining the number and position of fold lines on a sheet depending on a longitudinal dimension of a sheet, said control means further including signal generating means (75, 78) for providing a sheet length signal representative of the length of a sheet for selecting one program out of a number of programs stored in said memory (50) in accordance with said sheet length signal and in response to at least one of said "edge present" signals, said signal generating means (75, 78), said first and second sensors (4, 16) and said memory cooperating in said control means (35) for operating said reversible drive means to selectively drive said first, second, and third belt means (5, 6, 10) so that the direction of rotation of said drive means is in accordance with said selected folding program based on said sheet length signal as communicated to said memory by said signal generating means (75, 78), and wherein said drive means (8, 8') comprise a controlled motor (8') for driving said sheet supply rollers (3) at a controlled speed in said sheet feeding direction, and a reversible stepping motor (8) for operating said first belt means (5), said second belt means (6), and said third belt means (10) in a direction of rotation and in rotary steps in response to said control means (35) for folding a sheet in accordance with said selected one program.