Folder for rotary press

1. A variable cut-off length rotary printing machine, comprising:

a printing unit that can vary a printing length of a web by changing an outside diameter of a printing cylinder, and

a folding machine provided downstream of the printing unit of the rotary printing machine, said folding machine comprising:

a cut-off unit comprising:

a cut-off mechanism configured to cut off the web fed from said printing unit at a predetermined cut-off length position to form a sheet, and

a first belt conveyor comprising a pair of conveyor belts, a motor for driving the pair of conveyor belts and a speed control means for controlling a speed of the motor for nipping and conveying the cut sheet at a first speed by the pair of conveyor belts, wherein the speed control means is configured to set the first speed equal to a web conveying speed based upon the predetermined cut-off length;

a processor disposed downstream of said cut-off unit and configured to process the cut sheet conveyed at a constant second speed different from said first speed; and

a second belt conveyor disposed between said cut-off unit and said processor and partly directly overlapping the first belt conveyor, the second belt conveyor comprising a variable speed motor which can change a speed during conveyance of the sheet and at least one pair of conveyor belts configured to receive the cut sheet conveyed by said first belt conveyor, and convey said sheet to said processor at the constant second speed;

wherein said second belt conveyor is a variable speed conveyor configured to vary a sheet conveying speed during the conveyance of said sheet so that in receiving said sheet from said first belt conveyor, said sheet conveying speed becomes approximately equal to said first speed at which said sheet is conveyed in said first belt conveyor, and in conveying said sheet to said processor, said sheet conveying speed becomes approximately equal to said second speed at which said sheet is conveyed in said processor through changing the speed of said conveyor belts from said first speed to said second speed by changing the seed of said motor.

2. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said cut-off unit comprises a first cut-off mechanism for partially cutting said web; and a second cut-off mechanism, provided downstream of said first cut-off mechanism, for cutting off said sheet from said web by cutting uncut portions of said web that is not cut by said first cut-off mechanism.

3. The variable cut-off length rotary printing machine as set forth in claim 2 , wherein said first belt conveyor nips said web that is to be cut by said second cut-off mechanism, and said cut-off unit further comprises another belt conveyor comprising a pair of conveyor belts for nipping and conveying said web to said second cut-off mechanism.

4. The variable cut-off length rotary printing machine as set forth in claim 2 , wherein said folding machine further comprises a first relative-phase changer, interposed between said first cut-off mechanism and said second cut-off mechanism, for changing relative phases of rotation of said first cut-off mechanism and said second cut-off mechanism when varying a cut-off length of said web fed from said printing unit.

5. The variable cut-off length rotary printing machine as set forth in claim 2 , wherein said folding machine further comprises a scored-line forming mechanism, provided upstream of said first and second cut-off mechanisms, for forming a horizontally scored line in said web at a predetermined position; and a second relative-phase changer, interposed between said scored-line forming mechanism and said first cut-off mechanism, for changing relative phases of rotation of said scored-line forming mechanism and said first cut-off mechanism when varying a cut-off length of said web fed from said printing unit.

6. The variable cut-off length rotary printing machine as set forth in claim 4 , wherein said folding machine further comprises a scored-line forming mechanism, provided upstream of said first and second cut-off mechanisms, for forming a horizontally scored line in said web at a predetermined position; and a second relative-phase changer, interposed between said scored-line forming mechanism and said first cut-off mechanism, for changing relative phases of rotation of said scored-line forming mechanism and said first cut-off mechanism when varying a cut-off length of said web fed from said printing unit.

7. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said sheet conveying speed of said processor is faster than that of said first belt conveyor.

8. The variable cut-off length rotary printing machine as set forth in claim 7 , wherein the variable speed second belt conveyor is configured to receive the cut sheet at a speed approximately equal to the sheet conveying speed of said first belt conveyor, accelerate to a speed approximately equal to the sheet conveying speed of said processor, deliver the cut sheet to said processor at a speed approximately equal to the sheet conveying speed of said processor, decelerate to the sheet conveying speed of said first belt conveyor, and then receive a next cut sheet from said web.

9. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said processor comprises a discharger for discharging a sheet cut off by said cut-off unit or a folder for folding a sheet cut off by said cut-off unit along a crease perpendicular to a sheet conveying direction.

10. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said first belt conveyor, said second belt conveyor, said cut-off unit, and said processor are respectively driven by different motors, and a phase of each of said motors can be relatively varied.

11. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said folding machine further comprises an abutting portion, provided between said second belt conveyor and said processor, which a front end of said sheet abuts and by which a conveying phase of said sheet in said folder can be adjusted.

12. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said folding machine further comprises a third belt conveyor, provided downstream of said second belt conveyor and at an entrance portion to said processor, which comprises a pair of conveyor belts for receiving said sheet from said second belt conveyor and conveying said sheet to said processor at the sheet conveying speed of said processor.

13. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said folding machine further comprises a non-circular roller, provided at a position where said sheet is delivered from one of said two belt conveyors adjacent to each other to the other of said two belt conveyors, which guides one of a pair of conveyor belts and has a plurality of surface portions in which distances from a center of rotation to the surface portions are different.

14. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein the conveyor belts of said second belt conveyor are driven by non-circular rollers having a plurality of surface portions in which distances from a center of rotation to the surface portions are different.

15. The variable cut-off length rotary printing machine as set forth in claim 1 , wherein said cut-off unit comprises a saw cylinder and a receiving cylinder contacting the saw cylinder, an outer diameter of each of the saw cylinder and the receiving cylinder as well as a feeding speed of the web to the cut-off unit being changed when the cut-off length of the web is changed.

16. The variable cut-off length rotary printing machine as set forth in claim 15 , wherein the first and second belt conveyors are configured such that in changing the cut-off length of the web, the first conveyer is set to change a speed corresponding to the feeding speed of the web, and the second belt conveyer is set to change a speed substantially corresponding to the speed of the first conveyer in receiving the cut web from the first conveyer and to increase the speed to the constant second speed corresponding to the processor when delivering the cut web to the processor.