Sheet transport position and jam monitor

1. A sheet transport system comprising:

at least one sheet transporter that receives and hands off a sheet being transported by the system so as to transport the sheet from a fire position to a second position;

a plurality of sensors that generates signals responsive to a position of a sheet as it is transported by the transport system;

a display screen; and

a controller that receives the signals generated by the sensors and uses the signals to provide a real time visual display on the screen, of an image of a sheet, superimposed on an image of the transport system, as it moves through the transport system.

2. A sheet transport system according to claim 1 wherein the visual display shows the sheet in continuous motion moving through the transport system.

3. A sheet transport system according to claim 1 wherein visual display displays a plurality of such sheet images simultaneously as the sheets are transported by the transport system.

4. A sheet transport system according to claim 3 wherein each of said sheets is identified on said display by a designation of said sheet.

5. A sheet transport system according to claim 4 wherein the designation comprises identification numbers.

6. A sheet transport system according to claim 4 wherein if a malfunction occurs in the transport system and at a particular location in the transport system a sheet is improperly transported, the particular location is indicated on the display screen.

7. A sheet transport system according to claim 1 wherein the display screen is comprised in a video monitor.

8. A sheet transport system according to claim 1 wherein the sheet at least one transporter comprises:

at least one orifice through which air is aspirated to create a vacuum that grips a sheet when it is received by the transporter;

a vacuum system coupled to the at least one orifice controllable to aspirate air through the at least one orifice to grip the sheet;

at least one vacuum sensor that generates signals responsive to magnitude of vacuum at the at least one orifice; and

a controller that receives the signals generated by the at least one vacuum sensor and provides a signal indicative of a location of the sheet in the transport system from the signals.

9. A sheet transport system according to claim 8 wherein the vacuum system is controllable to release air to the at least one orifice to release the sheet.

10. A sheet transport system according to claim 8 wherein the controller uses signals from the at least one vacuum sensor to determine if a sheet being transported by a transporter of the at least one transporter is being transported properly.

11. A sheet sport system according to claim 8 wherein an orifice of the at least one orifice is a suction cup.

12. A sheet transport system according to claim 8 wherein the vacuum sensor is a pressure sensor.

13. A sheet tort system according to claim 8 wherein the vacuum sensor is a flow meter.

14. A sheet transport system according to claim 8 wherein the controller determines that a transporter of the at least one transporter is gripping a sheet being transported by the transport system and that the sheet is gripped properly if signals from a vacuum sensor of the at least one vacuum sensor indicate that vacuum sensed by the sensor is greater than a first pre-determined level of vacuum.

15. A sheet transport system according to claim 8 wherein the controller determines that a transporter of the at least one transporter is not gripping a sheet being transported by the transport system if signals from the at least one vacuum sensor indicate that vacuum sensed by the at least one vacuum sensor is less than a second pre-determined level of vacuum.

16. A sheet transport system according to claim 8 wherein the controller determines that a transporter of the at least one transporter is gripping a sheet being transported by the transport system, but that the sheet is gripped improperly, if signals from a vacuum sensor of the at least one vacuum sensor indicate that the vacuum sensed by the sensor is between the first and second vacuum levels.

17. A sheet transport system according to claim 1 wherein the at least one transporter comprises a plurality of sheet transporters.

18. A sheet transport system according to claim 17 wherein sheet transporters of the plurality of sheet transporters seriatim receive and hand off a sheet being transported by the system so as to transport the sheet from the first position to the second position.

19. A sheet transport system according to claim 1 wherein a transporter of the at least one transporter is a rotary transporter, which rotates about an axis to receive and hand off a sheet being transported by the transport system.

20. A sheet transport system according to claim 1 wherein the sheet transport system is a transport system that transports sheets printed in a printing system comprising at least one printing station and wherein the first and second positions are positions of the sheets in the printing system.

21. A sheet transport system according to claim 20 wherein at least one of the first and second positions is a position in a printing station of the at least one printing station.

22. A sheet transport system according to claim 21 wherein the printing station comprises an impression roller.

23. A sheet transport system according to claim 22 wherein the first position in the printing station is a position at which a sheet is removed from the impression roller.

24. A sheet transport system according to claim 22 wherein the second position in the printing station is a position at which a sheet is mounted on the impression roller.