Sheet transporting device, cutting device, printing press and corresponding method
The sheet transporting device of the invention includes: a transferring device ( 64 ) adapted to transfer a sheet ( 30 ), a conveying device ( 66; 66 A) for conveying a sheet transferred from the transferring device ( 64 ) onto the conveying device, and a controlling means ( 76 ) adapted to control the speed of the conveying device ( 66; 66 A) and defining a transfer cycle (CT). The controlling means ( 76 ) is adapted to slow down the conveying device ( 66 ) when a sheet is conveyed by the related conveying device and to accelerate the conveying device when no sheet is present on said conveying device. The invention can be used for the cutting devices of rotary printing machines.
1. A sheet transporting device comprising:
a transfer device transferring a sheet;
a first conveying device conveying a sheet transferred from the transfer device onto the first conveying device;
a controller controlling the speed of the first conveying device and defining a transfer cycle, the controller slowing the first conveying device when a sheet is being conveyed by the first conveying device, the controller including a device for identifying the position of a conveying element of the conveying device and generating a conveying device speed setpoint signal dependent on the identified position; and
accelerating the first conveying device when there is no sheet on the first conveying device.
2. The transporting device as recited in claim 1 , wherein during a transfer cycle, the first conveying device and the transfer device have a transfer phase in which a sheet is transferred onto the first conveying device and an output phase in which a sheet is set down by the first conveying device, and the controller accelerating the first conveying device between the output phase and the transfer phase and slowing a slowing device between the transfer phase and the output phase.
3. The transporting device as recited in claim 2 , wherein the controller drives the first conveying device at a constant speed during the transfer phase and during the output phase.
4. The transporting device as recited in claim 2 , wherein the controller drives the transfer device during the transfer phase at a first transfer speed and the conveying device at a second transfer speed which differs from the first transfer speed.
5. The transporting device as recited in claim 4 , wherein the first transfer speed is higher than the second transfer speed.
6. The transporting device as claimed in claim 4 , wherein the first transfer speed is equal to the second transfer speed.
7. The transporting device as recited in claim 1 , wherein the controller drives the transfer device at a constant speed throughout an entire transfer cycle.
8. The transporting device as recited in claim 1 , wherein the first conveying device is a slowing device that slows a sheet.
9. The transporting device as recited in claim 1 , wherein the first conveying device is a conveyor.
10. The transporting device as recited in claim 1 , further comprising a second conveying device, the transfer device transferring a sheet onto each of the first and second conveying devices alternately.
11. The transporting device as recited in claim 1 , further comprising a cutting device cutting a web into sheets and feeding the transfer device with sheets.
12. The transporting device as recited in claim 11 , wherein the transfer device is a counterpressure roller of the cutting device.
13. A sheet output device comprising:
a web input;
a sheet stacking device; and
a transporting device as recited in claim 11 .
14. A web offset rotary press comprising an output device as claimed in claim 13 .
15. A method of transporting sheets with the sheet transporting device recited in claim 1 comprising the following steps during a transport cycle:
transferring a sheet from the transfer device to the first conveying device;
slowing the first conveying device when there is a sheet placed on the first conveying device; and
accelerating the first conveying device when there is no sheet on the first conveying device.
16. The transporting method as claimed in claim 15 , further comprising the following steps:
during a transfer phase, transferring a sheet from the transfer device to the first conveying device at a transfer speed;
during an output phase, the first conveying device setting down a sheet at an output speed lower than the transfer speed;
between the transfer phase and the output phase, slowing the first conveying device; and
between the output phase and the transfer phase, accelerating the first conveying device.
17. The transporting method as recited in claim 16 , comprising, during the transfer phase or during the output phase, the step of driving the first conveying device at a constant transfer or output speed, respectively.
18. The transporting method as recited in claim 17 , comprising, during the transfer phase, the step of driving the transfer device at a first transfer speed and the first conveying device at a second transfer speed.
19. The transporting method as claimed in claim 18 , wherein the first transfer speed is higher than the second transfer speed.
20. The transporting method as claimed in claim 18 , wherein the first transfer speed is equal to the second transfer speed.
21. The transporting method as recited in claim 15 , comprising, prior to transferring the sheet, the step of cutting the sheet from a web.
22. The transporting device as recited in claim 1 , wherein the device identifying the position of a conveying element and generating a conveying device speed setpoint signal depending on the identified position is an electronic cam.