Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H23/00—Registering, tensioning, smoothing or guiding webs
  • B65H23/04—Registering, tensioning, smoothing or guiding webs longitudinally
  • B65H23/18—Registering, tensioning, smoothing or guiding webs longitudinally by controlling or regulating the web-advancing mechanism, e.g. mechanism acting on the running web
  • B65H23/188—Registering, tensioning, smoothing or guiding webs longitudinally by controlling or regulating the web-advancing mechanism, e.g. mechanism acting on the running web in connection with running-web
  • B65H23/1888—Registering, tensioning, smoothing or guiding webs longitudinally by controlling or regulating the web-advancing mechanism, e.g. mechanism acting on the running web in connection with running-web and controlling web tension
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2404/00—Parts for transporting or guiding the handled material
  • B65H2404/10—Rollers
  • B65H2404/11—Details of cross-section or profile
  • B65H2404/112—Means for varying cross-section
  • B65H2404/1122—Means for varying cross-section for rendering elastically deformable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2513/00—Dynamic entities; Timing aspects
  • B65H2513/10—Speed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
  • B65H2515/30—Forces; Stresses
  • B65H2515/31—Tensile forces
  • B65H2515/314—Tension profile, i.e. distribution of tension, e.g. across the material feeding direction or along diameter of web roll
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
  • B65H2515/30—Forces; Stresses
  • B65H2515/32—Torque e.g. braking torque
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2557/00—Means for control not provided for in groups B65H2551/00 - B65H2555/00
  • B65H2557/20—Calculating means; Controlling methods
  • B65H2557/26—Calculating means; Controlling methods with key characteristics based on open loop control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2557/00—Means for control not provided for in groups B65H2551/00 - B65H2555/00
  • B65H2557/20—Calculating means; Controlling methods
  • B65H2557/264—Calculating means; Controlling methods with key characteristics based on closed loop control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2801/00—Application field
  • B65H2801/03—Image reproduction devices
  • B65H2801/21—Industrial-size printers, e.g. rotary printing press

Definitions

• the present invention relates generally to web printing presses and more particularly to a method and apparatus for controlling the tension of the web in a printing press including two or more sets of nip rollers with deformable covers.
• Web printing presses print a continuous web of material, such as paper.
• the web travels through nips formed by opposing nip rollers.
• the web is moved on its way by driven nip rollers which are driven by respective nip roller drivers.
• Tension in the web must be maintained within a desired range in order to achieve smooth operation of the printing press. At the same time, the velocity of the web, and hence the rotational speed of nip rollers, must be held relatively constant to achieve good print product quality. Tension in a web span between two nips can be adjusted by controlling the speed of the nip roller driver in the downstream nip.
• nip rollers have been used in conventional web printing presses. Some nip rollers were formed with a deformable surface layer such as urethane. Nip rollers with a deformable surface were found to provide less than ideal operation because of uneven ribbon-to- ribbon tension in upstream web spans.
• nip rollers formed with a deformable surface such as microcellular foamed urethane were introduced (see, U.S. Patent Publication No. 2006/0157924 Al published on July 20, 2006 and incorporated herein by reference).
• Nip rollers with this type of deformable surface layer were found to overcome the uneven ribbon-to-ribbon tension problem of the earlier nip rollers.
• any nips with non-rigid covers have an effective gain that is a function of the tension difference across the nip roller, so that if the tension of the web downstream from the nip roller is changed, the tension of the upstream web will also change requiring an additional tension adjustment.
• An object of the present invention is to provide a method and apparatus which allows for adjustment of the tension of a downstream span of web without affecting the tension of an upstream span of web.
• the present invention provides a method for controlling web tension in a web printing press having a plurality of sets of deformable nip rollers, each set of deformable nip rollers driven by a separate driver, the web passing sequentially through each set of deformable nip rollers, each adjacent set of deformable nip rollers forming a web segment therebetween.
• a first characteristic of the driver of a downstream set of deformable nip rollers is adjusted to set the tension of a first web segment which is between the downstream set of deformable nip rollers and an upstream set of deformable nip rollers.
• a first characteristic of the driver of the upstream set of deformable nip rollers is adjusted to maintain a constant tension on a second web segment which is immediately preceding the upstream set of deformable nip rollers.
• a second characteristic of the second web segment is measured and the first characteristic of the driver of the upstream set of deformable nip rollers is adjusted based on the measurement of the second characteristic.
• the present invention also provides an apparatus for controlling web tension in a web printing press having a plurality of sets of deformable nip rollers, each set of deformable nip rollers driven by a separate driver, the web passing sequentially through each set of deformable nip rollers, each adjacent set of deformable nip rollers forming a web segment therebetween.
• the apparatus includes a circuit for adjusting a first characteristic of the driver of a downstream set of deformable nip rollers to set the tension of a first web segment which is between the downstream set of deformable nip rollers and an upstream set of deformable nip rollers.
• the apparatus also includes a controller for adjusting a first characteristic of the driver of the upstream set of deformable nip rollers to maintain a constant tension on a second web segment which is immediately preceding the upstream set of deformable nip rollers.
• the apparatus also includes a sensor for measuring a second characteristic of the second web segment and the controller adjusts the first characteristic of the driver of the upstream set of deformable nip rollers based on the measurement from the sensor.
• the first characteristic may be the rotational speed of the driver.
• the second characteristic may be the tension of the second web segment, the speed of the second web segment, or the amount of torque in the driver of a set of deformable nip rollers immediately preceding the upstream set of deformable nip rollers.
• FIG. 1 is a block diagram of an embodiment of the present invention having closed loop control based on a feedback signal provided from a tension sensor;
• FIG. 2 is a block diagram of an embodiment of the present invention having closed loop control based on a feedback signal provided from a velocity sensor;
• FIG. 3 is a block diagram of an embodiment of the present invention having closed loop control based on a feedback signal provided from a torque sensor;
• FIG. 4 is a block diagram of an alternative embodiment of the present invention having open-loop control.
• FIG. 1 shows a block diagram of an apparatus for setting the tension of a downstream web without affecting the tension of an upstream web in a web printing press 10 according to one presently preferred embodiment of the invention.
• Web 12 is moved by driven nips 22, 28 and 34 in the direction indicated by arrow 14.
• Nips 22, 28 and 34 are formed by nip rollers 20 and 24, 26 and 30, and 32 and 36, respectively.
• Nip rollers 22 and 24, 26 and 30, and 32 and 36 rotate as indicated by arrows 27 and are formed with a deformable surface as described above and in more detail in U.S. Patent Publication No. 2006/0157924 Al .
• Nip rollers 20, 26 and 32 in Fig. 1 are driven by nip roller drivers 38, 40 and 39, respectively.
• Nip roller drivers 38, 40 and 39 may be, for example, electric motors, or other type of suitable drivers.
• Drive controllers 48, 50 and 49 provide control signals to nip roller drivers 38, 40 and 39, respectively, to control the rotational speed of respective nip rollers 20, 26 and 32.
• the control signals are provided from controller 70 to the drive controllers 48, 50 and 49 on respective signal lines 58, 60 and 59, respectively.
• Upstream web span 16 is formed between nips 22 and 28, while downstream web span 18 is formed between nips 28 and 34.
• additional nips may be provided in the printing press 10 within the context of the present invention, and the principles of this invention apply in that event as well.
• a tension sensor 92 directly measures the tension in upstream web span 16 and provides a corresponding output signal on line 93 to controller 70.
• Controller 70 also includes an input 60 which is used by an operator to set the tension of downstream web span 18 according to principles of the invention.
• closed loop control is used to maintain the tension of upstream web span 16 at a constant value when an operator desires to change the tension of the downstream web span 18.
• controller 70 first calculates an updated value for the control signal 59 so that drive controller 49 will adjust the rotational speed of nip roller driver 39 thereby changing the tension of downstream web span 18 to the desired value. Since the change in tension of downstream web span 18 would also result a change in the upstream web span 16 when using deformable nip roller, controller 70 also changes the rotational speed of nip roller driver 40 in a manner that will maintain the tension of upstream web span 16 at a constant value.
• controller 70 receives a signal on line 93 from tension sensor 92, and compares the received tension signal with the desired tension level and adjusts, in a closed loop manner, the control signal 60 so that the result of the comparison between the received tension signal and the desired tension level is zero. In this manner, whenever an operator changes the tension of downstream web 18, the tension of upstream web 16 will be automatically kept constant by closed loop control via the feedback signal provided from tension sensor 92. By maintaining the tension on upstream web span 16 at a constant level, the change of tension on downstream web span 18 is invisible to all preceding nips and spans.
• Fig. 1 shows a single controller which separately sets and controls the speed of nip roller drivers 38, 39 and 40
• each nip roller driver 38, 39 and 40 could be separately controlled, and that the closed-loop control is only applied in this illustrative embodiment to control the nip roller driver which is upstream from the web span having its tension changed.
• the techniques of this invention can be applied to allow adjustment of any span in a printing machine without affecting the tension of any other span.
• nip roller drives 38 and 39 are shown being set by controller 70, but could alternatively could be set by other means known to one of ordinary skill in the art.
• Fig. 1 shows a controller 70 which compares the signal from tension sensor 92 to a desired value to calculate the feedback control signal 60 to apply to drive controller 50, as one of skill in the art would readily recognize, this could alternatively be done in the analog domain using a comparator and other ancillary circuitry, where the comparator compares an analog signal from the tension sensor 92 to a predetermined value representing the desired tension setting.
• drive controllers 48, 49 and 50 as separate from controller 70, as one of ordinary skill in the art will understand, the drive controller functions could alternatively be implemented either within controller 70 or separately within nip roller drivers 38, 39 and 40.
• Fig. 2 shows a first alternative embodiment of the present invention which also relies on closed loop control to maintain the tension of upstream web span 16 at a constant value when the tension of downstream web span 18 is intentionally changed by the operator.
• a velocity sensor 95 is provided to monitor the velocity of upstream web span 16 and provide a corresponding velocity signal 98 to controller 70 (and tension sensor 92 is omitted).
• controller 70 compares the measured velocity signal 98 to the desired velocity value and generates a control signal 60 for the drive controller 50 connected to nip roller driver 40 which, because of the closed loop nature of the system, will cause the difference between the measured velocity signal 98 and the desired velocity value to quickly become zero, even after the tension on downstream web span 18 is changed.
• Fig. 3 shows a second alternative embodiment of the present invention which also relies on closed loop control to maintain the tension of upstream web span 16 at a constant value when the tension of downstream web span 18 is intentionally changed by the operator.
• a torque sensor 90 is provided in nip roller driver 38 to provide a torque signal 57 to controller 70 (and tension sensor 92 is omitted).
• controller 70 compares the measured torque signal 57 to a toque value that corresponds to the desired tension on upstream web span 16 and generates a control signal 60 for the drive controller 50 connected to nip roller driver 40 which, because of the closed loop nature of the system, will cause the difference between the measured torque signal 57 and the desired torque value to quickly become zero, even after a change on the tension on downstream web span 18.
• Fig. 4 shows a third alternative embodiment of the present invention which, unlike the other embodiments, does not rely on closed loop control to maintain the tension of upstream web span 16 and thus does not require any sensor to monitor the tension of upstream web span 16. Instead, when the operator inputs a tension change for downstream web span 18, controller 70 automatically calculates the amount of change necessary for both control signal 59 and control signal 60 based on characteristics stored in memory. These characteristics can be defined empirically or using predictive models, as understood by one of ordinary skill in the art, and, for example, control signal 60 could be a fixed percentage of control signal 59.

Landscapes

• Controlling Rewinding, Feeding, Winding, Or Abnormalities Of Webs (AREA)
• Inking, Control Or Cleaning Of Printing Machines (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=42336135

Family Applications (1)

Country Status (4)

Families Citing this family (5)

Family Cites Families (16)

• 2009
  • 2009-01-22 US US12/357,718 patent/US20100181360A1/en not_active Abandoned
• 2010
  • 2010-01-21 CN CN201080004884.8A patent/CN102292212B/zh not_active Expired - Fee Related
  • 2010-01-21 EP EP10733851A patent/EP2389291A4/de not_active Withdrawn
  • 2010-01-21 WO PCT/US2010/021656 patent/WO2010085563A1/en not_active Ceased

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