Automated printing press with reinsertion registration control

Claims

From the above it will be apparent to those skilled in the art that various modifications and additions can be made without departing from the principles of the present invention. Therefore, what is claimed is:

1. A flexographic printing press having a plurality of printing stations wherein each of the printing stations comprises:

a frame;

an impression roller rotatably mounted to the frame;

a drive gear mounted to said impression roller;

a print carriage having a print roller rotatably mounted thereon, the print carriage being movably mounted to the frame to advance the print roller in a direction toward the impression roller and to retract the print roller in a direction away from the impression roller;

a drive gear mounted to said print roller;

a gear train driveably interconnecting the impression roller and the print roller and including a swing gear assembly having a housing and first and second gears mounted for rotation to the housing and in driving engagement with one another, wherein said housing is pivotal about the first gear to accommodate relative movement of said print roller and impression roller toward and away from one another, said swing gear assembly including an output gear having teeth engageable with one of said drive gears;

a pivoting and biasing mechanism coupled to said housing and operative to pivot said housing such that said output gear maintains biased engagement with said one of said drive gears; and

a first bearer ring rotatable with and separate from said output gear and a second bearer ring rotatable with and separate from said one of said drive gears, said first and second bearer rings engaging one another during biased engagement of said output gear and said one of said drive gears such that said output gear is maintained a fixed distance from said one of said drive gears.

2. The flexographic printing press of claim 1 wherein:

the print carriage is moveable on the frame between a print position at which the print roller is in printing contact with a substrate between the print roller and the impression roller and a throw-off position at which the print roller is out of printing contact with a substrate between the print roller and the impression roller; and,

said pivoting and biasing mechanism together with said first and second bearer rings maintain the fixed distance between said output gear and said drive gear during movement of the print roller between the print position and throw-off position.

3. The flexographic printing press of claim 1 wherein:

said pivoting and biasing mechanism comprises a rotary actuator which is operative to rotate said housing between a position in which said output gear is engaged with said drive gear and a position in which said output gear is disengaged from said drive gear.

4. The flexographic printing press of claim 3 further comprising:

a curved gear rack fastened to said housing; and

a pinion gear in engagement with said rack and connected for rotation with an output shaft of said rotary actuator.

5. The flexographic printing press of claim 1 wherein:

said second gear is operatively coupled for rotation with said output gear and said output gear is engageable with the drive gear of said print roller.

6. The flexographic printing press of claim 1 wherein:

said pivoting and biasing mechanism swings said housing along a path of movement toward and away from said drive gear, said path including movement generally tangential to said drive gear and including a first position in which said output gear is engaged with said drive gear and a second position in which said output gear is disengaged from said drive gear.

7. The flexographic printing press of claim 6 wherein:

the print carriage is moveable on the frame between a print position at which the print roller is in printing contact with a substrate between the print roller and the impression roller and a backed-off position at which the print roller is out of printing contact with a substrate between the print roller and the impression roller; and

the pivoting and biasing mechanism maintains the output gear in the first position when the print carriage is in the print position and in the second position when the print carriage is in the backed-off position.

8. The flexographic printing press of claim 1 further comprising:

a carriage positioning motor connected between the print carriage and the frame to advance and retract the print roller a controlled distance respectively toward and away from the impression roller in response to control information carried by a control signal; and,

a controller having an output connected to the carriage positioning motor and having a programmable memory configured to cause the controller to generate the control signal carrying control information representing the controlled distance from the print roller to a selected one of a plurality of different positions of the print roller relative to the impression roller.

9. The flexographic printing press of claim 1 wherein:

the gear train further includes a harmonic drive unit connected between the impression roller and the print roller, the harmonic drive unit being operative to circumferentially adjust the print roller relative to the impression roller.

10. The flexographic printing press of claim 9 wherein:

said harmonic drive unit further includes a differential for changing the phase between an input and an output of said harmonic drive unit and therefore between said print roller and said impression roller; and,

the press further includes a servo motor connected to said differential to drive said differential in response to a circumferential adjustment control signal.

11. The flexographic printing press of claim 10 further comprising:

a registration system that includes a controller operable to supply the circumferential adjustment control signal to the servo motor in accordance with circumferential registration differences between printing stations to maintain circumferential registration of the print and impression rollers of multiple printing stations.

12. An automated flexographic printing press having a plurality of printing stations wherein each of the printing stations comprises:

a frame;

an impression roller rotatably mounted to the frame;

a print carriage having a print roller rotatably mounted thereon, the print carriage being movably mounted to the frame to advance in a direction toward the impression roller to a printing position at which the print roller is in printing contact with a substrate between the print roller and the impression roller and to retract in a direction away from the impression roller to at least one non-printing position, including a throw-off position, at which the print roller is out of printing contact with the substrate;

a swing gear assembly driveably interconnecting the print roller and the impression roller, the assembly including mating gears maintained in a precise mating tolerance when the assembly is in a fully engaged condition, the assembly being swingably mounted so as to be maintainable in the fully engaged condition when the print roller is in the printing position, in the throw-off position, or in a position therebetween, so as to maintain synchronized motion and circumferential registration between the print and impression rollers when in such positions;

at least one print carriage servo motor connected between the frame and the print carriage and operable to advance and retract the carriage in response to a print roller position control signal;

a memory having information stored therein of printing position and non-printing position settings of the servo motor representing locations of the respective positions of the rollers on the frame;

an operator interface having operator command inputs thereon, including a non-printing position command input to select the movement of the carriage to the non-printing position, a print position command input to select the movement of the carriage to the printing position, and incremental adjustment command inputs; and,

a processor programmed to:

selectively adjust the information stored in the memory in response to the incremental adjustment command inputs, and

generate the print roller control signal to:

cause the carriage to move to the print position in response to the print position command input and the stored information, as adjusted, and

cause the carriage to move to the non-printing position in response to the non-printing position command input and the stored information, as adjusted.

13. The flexographic printing press of claim 12 wherein:

the memory has information stored therein of print roller size and of substrate thickness;

the operator interface has operator command inputs thereon that include data inputs for changing the information stored in the memory of print roller size and of substrate thickness; and

the processor is programmed to generate the print roller control signal at least partially in response to the print roller size and substrate thickness information in the memory to adjust at least the print position to accommodate changes in at least one of substrate thickness and print roller size;

the mating gears of the assembly being maintained in a precise mating tolerance when the assembly is in a fully engaged condition with an adjusted print position.

14. The flexographic printing press of claim 12 further comprising:

a central computer connected in data communication with the processors of the printing stations to remotely monitor and operate the operator interface at each printing station.

15. The flexographic printing press of claim 12 wherein:

the processor is programmed to generate the print roller control signal to cause the carriage to move to the print position in response to the print position command and the stored information if and only if the substrate is moving, and to cause the carriage to move to the throw-off position when the substrate is not moving, while maintaining the synchronized motion and circumferential registration.

16. The flexographic printing press of claim 12 wherein each station comprises:

at least two servo motors connected between the frame and the print carriage, one to each side of the carriage, and operable in synchronism to advance and retract the carriage, each in response to a separate print roller position control signal, while maintaining constant an angle between the print roller and the impression roller, and operable differentially to change the angle between the print roller and the impression roller;

the memory having information stored therein of separate printing position and non-printing position settings of the servo motors representing the locations of the printing position and non-printing position on the frame; and,

the operator interface having operator command inputs thereon by which to select simultaneous and separate operation of the servo motors.

17. The flexographic printing press of claim 12 wherein each station comprises:

an inking carriage having an anilox roller and a metering element mounted thereon, the inking carriage being movably mounted to the printing carriage to advance in a direction toward the print roller to an inking position at which the print roller is in ink transferring contact with the anilox roller and to retract in a direction away from the print roller to at least one idle position at which the anilox roller is out of inking contact with the print roller;

at least one anilox carriage servo motor connected between the inking carriage and the print carriage and operable to advance and retract the inking carriage on the print carriage in response to an anilox roller position control signal;

the anilox roller being operatively connected with the print roller to be driven with the print roller when the print roller is in the print position;

an inking assembly drive connected to the anilox roller and operable to independently rotate the anilox roller when the anilox carriage is in the idle position;

the memory having information stored therein of inking position and idle position settings of the servo motor representing locations of the respective positions of the anilox roller on the print carriage; and

the processor being programmed to generate the anilox roller control signal in response to operator commands from the inputs and the stored information.

18. The flexographic printing press of claim 17 wherein:

the servo motors are each digital control signal responsive stepper motors and the stored information corresponds to pulse counts of control signals to the stepper motors.

19. An automated flexographic printing press comprising:

a plurality of distinct printing stations each for transferring at least one component part of a series of composite images at spaced apart locations along the length of a continuous substrate running therethrough, each of printing stations comprising, located thereat:

(a) a frame;

(b) an impression roller mounted for rotation on the frame to back the substrate;

(c) a print roller rotatably mounted with respect to the frame to print one component part of the image on the substrate being backed by the impression roller;

(d) a gear train driveably interconnecting the impression roller and the print roller and including a harmonic drive unit connected between the impression roller and the print roller, said harmonic drive unit having a differential input and being operable in response to the differential input to vary the circumferential motion of the print roller relative to the impression roller;

(e) a stepper motor having an output connected to the differential input of the harmonic drive to drive the differential input in response to a digital control signal to circumferentially incrementally adjust the print roller relative to the impression roller;

(f) a digital encoder responsive to the angular position of the impression roller at the respective station, the encoder being configured and mounted to produce a signal representing the angular position of the impression roller to an accuracy of within 1/5000 of a revolution thereof;

(g) an optical sensor operative to produce a signal responsive to the location relative to the impression roller of a previously printed component part of the image on substrate;

(h) a print roller position sensor operative to produce a signal responsive to the angular position of the print roller relative to the frame; and

(i) a registration controller operable in response to the signals from the encoder and the sensors to calculate a circumferential registration difference between the web and the print roller, to generate, as a result of the calculation, the control signal, and to supply the control signal in the form of a pulse stream to the stepper motor in accordance with circumferential registration difference to maintain circumferential registration among component parts of the images.

20. The printing press of claim 19, the registration controller includes:

a counter having an input connected to the encoder and operable to count pulses from the encoder;

logic responsive to each of the sensors for sampling the content of the counter in response to a signal from each sensor; and

the controller being operable to calculate the circumferential registration difference by subtracting one sampled counter content from the other.

21. The printing press of claim 20 wherein the logic is interrupt logic.

22. The printing press of claim 19, wherein:

the registration controller includes program logic to spread correction pulses over the revolution of the print roller.

23. The printing press of claim 19, wherein:

the registration controller includes program logic to implement an entire correction over one revolution of the print roller.

24. The printing press of claim 19, further comprising:

a servo motor connected to move the print roller axially relative to the frame and transverse to the substrate;

the optical sensor being further responsive to the transverse position of a previously printed component of the image on the substrate; and

the controller being operable to actuate the servo motor in response to the optical sensor to axially move the print roller transverse of the web to correct axial registration errors of component parts being applied.

25. The printing press of claim 19, wherein:

the previously printed component part of the image includes a mark that includes with a first bar disposed relative at an angle relative to at least one second bar; and

the optical sensor is operative to produce information to the controller of the relative distance between points on the first and second bars.

26. The printing press of claim 25, wherein:

the mark is generally "Z"-shaped including two second bars interconnected by the first bar.

27. The printing press of claim 25 further comprising:

an optical sensor positioned adjacent the web so as to sense the points on each of the bars; and

wherein the controller is operable, in response to a signal from the optical sensor, to determine the transverse position of the web by calculating the distance between the sensed points.

28. The printing press of claim 19 wherein the digital encoder at each station is responsive to the angular position of the impression roller at the respective station and is configured and mounted to produce a signal representing the angular position of the impression roller to an accuracy of within 1/20000 of a revolution of the impression roller.

29. The printing press of claim 19 wherein each impression roller has an axial shaft fixed thereto and the digital encoder at each station is mounted to the shaft so as to produce the signal representing the angular position of the impression roller to the recited accuracy.

30. An automated flexographic printing press having a plurality of distinct printing stations each for transferring at least one component part of a series of composite images at spaced apart locations along the length of a continuous substrate running therethrough, each of printing stations comprising:

a frame;

an impression roller mounted for rotation on the frame to back the substrate;

a print roller rotatably mounted with respect to the frame to print one component part of the image on the substrate being backed by the impression roller;

a servo motor connected to move the print roller axially relative to the frame and transverse to the substrate;

a transverse position sensor operative to generate a timed sensing signal in response to the transverse position of a previously printed component of the image on the substrate; and

a controller operable to actuate the servo motor, in response to the timing of the sensing signal to calculate the transverse position of the substrate and to axially move the print roller transverse of the substrate.

31. The printing press of claim 30, wherein:

the previously printed component part of the image includes a mark that includes a first bar disposed at an angle relative to at least one second bar;

the transverse position sensor being operative to produce information to the controller of the relative distance between points on the first and second bars.

32. The printing press of claim 31, wherein:

the mark is generally "Z"-shaped including two second bars interconnected by the first bar.

33. The printing press of claim 32 wherein:

the sensor is positioned adjacent the web so as to sense points on each of the first bar and the two second bars and is operative to send signals to the controller containing information of the relative distances between different pairs of the first and second bars; and

the controller is operable, in response to the signals from the sensor, to determine the transverse position of the web by calculating the relative distances between the sensed points.

34. An automated printing press comprising:

a plurality of printing stations each for transferring one component part of at least one composite image at spaced locations along the length of a continuous substrate when the substrate is extended along a path through the stations, each of the stations having a frame, an impression roller rotatably mounted to the frame and a print roller rotatably mounted on a carriage adjustably supported on the frame to contact the substrate at a print position along the path;

the path between print positions having more than one possible length;

a memory having stored therein digital information corresponding to the length of the paths from each print position to at least one other print position;

each station having a drive train drivably connected to the print roller and the impression roller thereof to drive the rollers at a circumferential speed that corresponds to the lineal speed of the substrate at the station, the drive train including a differential gear unit having a motor connected to a differential input thereof and operative to differentially move the print roller in relation to the substrate in response to a control signal;

each station having associated therewith a memory having stored therein data relating to the size of the print roller at the respective station; and

each station having located thereat a registration controller operative to supply the control signal to the motor to alter the registration of the print roller relative to the substrate, the controller being operative, in response to a preregistration command, to obtain the path length information relating to the respective station and the data relating to the size of the print roller at the respective station, to calculate therefrom a preregistration angle of orientation of the print roller for the station, and to generate the control signal to cause the differential gear unit to move the print roller of the station to the preregistration angle of orientation.

35. A method of preregistering the print rollers of a flexographic press having a plurality of printing stations each for transferring one component part of at least one composite image at spaced locations along the length of a continuous substrate extending along a path through the stations, wherein each of the stations includes an impression roller and print roller pair located at a position along the path that is spaced from the positions of other roller pairs by distances that may vary, the method comprising the steps of, at a each of a plurality of the stations:

receiving and storing in a memory location for the station digital information relating to the distance along the path of the position of the roller pair of the station from the position of the roller pair of another station;

receiving and storing in a memory at each respective station data relating to the size of the print roller at the station;

from the information of relative position and the data of a print roller size stored for the station, calculating a preregistration angle corresponding to a remainder that would result by dividing a distance along the path between roller pair positions by a print roller circumference at the respective station;

sensing a reference moveable with the print roller and determining thereby the angular orientation of the print roller at the station; and

rotating the print roller at the station to the calculated preregistration angle.

36. A method of controlling the registration of a plurality of component parts of each of a plurality of composite images printed along the length of a continuous substrate, the method comprising the steps of:

providing a printing press having a plurality of printing stations, each station having a rotatably mounted printing element thereat having a fixed repeat length on the circumference thereof;

inserting in the printing press and consecutively through the plurality of printing stations a continuous substrate having a plurality of copies of at least one component part of a composite image preprinted along the length thereof, each copy of the preprinted at least one component part being located on a lineal repeat length of the continuous substrate that tends to vary from the fixed repeat length of the printing element;

running the inserted continuous substrate consecutively through the plurality of stations at a predetermined lineal speed while rotating the printing elements at each of the stations at a respective circumferential speed to print a respective additional component part of the composite image onto each of the preprinted at least one component parts along the substrate;

measuring a series of the lineal repeat lengths along the continuous substrate running through the stations, and generating a measurement signal representative of a plurality of lineal repeat length measurements;

calculating separately, for each station, in response to the measurement signal, a correction value representing the predicted difference between the fixed repeat length and the lineal repeat length of the next preprinted at least one component part to be run through the respective station, and generating a control signal carrying a separately calculated correction value for each station; and

separately controlling the actuation of circumferential adjustment means at each station in response to the control signal and in accordance with the respective correction value, so as to automatically change the circumferential speed of the respective printing element relative to the lineal speed of the continuous substrate in order to correct for variations between the lineal repeat lengths of the preprinted at least one component parts and component parts being printed by the printing element at the respective station.

37. The method of claim 36 wherein:

the measurement step includes the step of sensing at each station the relative lineal positions of preprinted at least one component parts relative to the circumferential position of the printing element at the respective station;

the calculating step includes the step of separately calculating for each station from the sensed relative lineal positions a circumferential registration error; and

the controlling step includes the step of separately controlling at each respective station the actuation of the respective circumferential adjustment means to automatically change the relative circumferential position of the printing element at the respective station relative to the sensed lineal position of the preprinted at least one component part so as to correct for the respective circumferential registration error.

38. The method of claim 36 wherein:

the measuring step includes the step of separately measuring at each station, the lineal repeat lengths of component parts running through each respective station and generating a respective one of a plurality of separate measurement signals in response thereto, each corresponding to a respective series of component parts run through the respective station; and

the calculating step includes the step of separately calculating each correction value in response to the respective measurement signal.

39. The method of claim 36 wherein:

the measuring step includes the step of digitally representing each of the measurements in discrete measurement data; and

the controlling step includes the step of incrementally controlling the actuation of circumferential adjustment means at each station in response to the respective control signal so as to automatically change the average circumferential speed of the respective printing element relative to the lineal speed of the continuous substrate by a series of discrete rotational movements spaced over a rotation of the pr