Patent Application
20070277691
A preferred embodiment of the present invention will be elucidated with reference to the drawings, in which:
Controllers 20, 22 maintain similar motor velocities for corresponding motors 30, 32. At a nip 60 a force develops between blankets 42, 52 when blankets 42, 52 contact each other. Controllers 20, 22 try to maintain similar angular velocities while blankets 42, 52 try to maintain similar surface velocities due to the contact between the blankets. If the diameters of blankets 42 and 52 are different the torque differs at the motors 30, 32.
After blankets 42, 52 are cleaned of ink, paper or other buildup accumulated from the offset printing process, initial torques for motors 30, 32 are determined by controllers 20, 22 respectively, when blankets 42, 52 are thrown off, before contact. Processor 90 stores the torque data determined by controllers 20, 22. A second set of torque data are determined and stored in processor 90 when blankets 42, 52 are thrown on.
Processor 90 compares the torque difference between controllers 20 and 22 before and after blankets 42, 52 are thrown on and determines if the torque difference greatly increases once blankets 42, 52 are contacting. A large difference in torque after blankets 42, 52 contact signals a large difference in blanket diameter. The controller 20, 22 that determines the larger difference in torque between the first and second set of torque measurements is connected to the blanket cylinder 44, 54 with the larger diameter blanket 42, 52. Thus, processor 90 can detect if blankets 42, 52 are incorrectly matched sized or manufactured and which blanket 42, 52 is larger or smaller.
An operator via an operator interface may input a predetermined set of data. The set may include a predetermined setpoint or setpoints for measurements acceptable for printing corresponding to, for example, torque measured in motors 30, 32. Thus, processor 90 compares the predetermined setpoints with the torque measured in motors 30, 32. Processor 90 alerts an operator if data is outside a predetermined setpoint. If applicable, processor 90 alerts an operator which blanket 42, 52 is larger or smaller.
An operator uses information collected by processor 90 to determine which blanket 42, 52 to remove. Operator may choose to remove the larger blanket, for example upper blanket 42. Operator replaces upper blanket 42 with reference blanket 62. Torques are determined when blankets 52, 62 are thrown on contact.
If the new torque data are acceptable, as defined by the set of predetermined data inputted by the operator, then existing blanket 52 is acceptable for use in the printing process. The operator can replace reference blanket 62 with a new or existing blanket known to be suitable for use in the printing process. The removed blanket 42 may be discarded or marked larger and saved for alternative use.
Alternatively, torque data may be outside the set of predetermined data inputted by the operator. If controller 20 determines a torque reading higher then controller 22, reference blanket 62 is larger than blanket 52. Thus, blanket 52 must be replaced with a blanket of suitable size. Blanket 52 may be discarded or marked smaller and saved for alternative use. Alternatively, if controller 20 determines a torque reading smaller then controller 22, reference blanket 62 is smaller than blanket 52. Thus, blanket 52 must be replaced with a blanket of suitable size. Blanket 52 may be discarded or marked larger and saved for alternative use resulting in reduced waste.
Thus, processor 90 monitors torque differences, allows for an online detection system before printing occurs and allows for verification to eliminate blanket diameter differences as the cause of poor print quality.
An additional embodiment of the present invention may determine and record a history of torque readings while printing. Processor 90 can monitor variables such as the increase in torque and change in direction over time. These variables can be compared to reference data and tolerances to determine when blankets need washing or signal potential problems. Thus, blankets can be cleaned or investigated before a printing problem may occur.
Differences in blanket construction may also cause torque differences, so it is also desirable to monitor torque differences due to blanket construction. Furthermore, the same technique may be employed by blanket manufacturers as a method of quality control to verify blanket diameters and construction.
In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.
