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
  • B65H23/042—Sensing the length of a web loop
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H20/00—Advancing webs
  • B65H20/30—Arrangements for accumulating surplus web
  • B65H20/32—Arrangements for accumulating surplus web by making loops
  • B65H20/34—Arrangements for accumulating surplus web by making loops with rollers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H35/00—Delivering articles from cutting or line-perforating machines; Article or web delivery apparatus incorporating cutting or line-perforating devices, e.g. adhesive tape dispensers
  • B65H35/04—Delivering articles from cutting or line-perforating machines; Article or web delivery apparatus incorporating cutting or line-perforating devices, e.g. adhesive tape dispensers from or with transverse cutters or perforators
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2511/00—Dimensions; Position; Numbers; Identification; Occurrences
  • B65H2511/10—Size; Dimensions
  • B65H2511/11—Length

Definitions

• the present invention relates to a web cutting apparatus, especially suitable for cutting the printed web output from a web-fed printing machine, into sheets.
• a web sizing intermittent feeder of this type is shown in the PATENT ABSTRACT JP 59 138 550 A.
• Such an apparatus may only be capable of cutting with an accuracy of, say, ⁇ 0.5 mm. In some applications a higher accuracy of, say, ⁇ 0.2 mm is required.
• the inaccuracy of the prior art devices derives, in part, from variations in the speed of the web leaving the printer, slippage of the web over the drive rollers, variations in the thickness of the web and variations in the elasticity of the web, possibly as a result of changing environmental conditions.
• upstream and downstream measuring devices for measuring the nominal length of the web fed into and from the web buffer, to enable the length of the web in the web buffer to be calculated and a control device to control operation of the downstream web drive and of the cutting station, thereby to enable cutting of the web at the cutting station at predetermined locations on the web.
• a web cutting apparatus comprising an upstream web drive for continuously feeding a web to be cut into a web buffer, and a downstream web drive for intermittently feeding the web from the buffer to a cutting station, characterised by an upstream measuring device for measuring the nominal length of the web fed into the web buffer, a downstream measuring device for measuring the nominal length of the web fed from the web buffer, and a control device responsive to information received from the upstream and downstream measuring devices to calculate the length of the web in the web buffer and to control operation of the downstream web drive and of the cutting station, in response thereto, thereby to enable cutting of the web at the cutting station at predetermined locations on the web.
• a method of cutting a web comprising continuously feeding a web into a web buffer with an upstream web drive, intermittently feeding the web from the buffer to a cutting station with a downstream web drive, and cutting the web at the cutting station, characterised by calculating the length of the web in the web buffer by measuring the nominal length of the web fed into the buffer and measuring the nominal length of the web fed from the buffer, and controlling the operation of the downstream web drive and the cutting station in response thereto, thereby to enable cutting of the web at the cutting station at predetermined locations on the web.
• the buffer may comprise a movable balance roller over which the web passes.
• a position sensing device such as a servo potentiometer, may be included for determining the position of the movable roller and supplying information relating to the sensed position to the control device.
• the length of the web in the web buffer may theoretically be calculated from the difference between the nominal length of web fed into the buffer and the nominal length of web fed from the buffer, a number of factors contribute to the possibility of this calculation being in error. For example, slippage of the web at the upstream web drive may result in a shorter length of web being fed into the buffer. Slippage of the web at the downstream web drive may result in a shorter length of the web being fed from the buffer. Stretching of the web may result in a longer web length in the buffer.
• the apparatus may further comprise a sensor positioned between the downstream web drive and the cutting station to sense timing marks located on the web, the control device being responsive to information received from the sensor.
• signals from the sensor are responded to only during a period of time within which a timing mark is expected to arrive at the sensor. That is, the control device effectively opens a sensor window for a period when a timing mark is expected.
• timing marks While it is known to provide timing marks in the margins of the printed web, where no other printing takes place, some applications prefer not to waste this space, but rather to provide the timing marks between the images.
• the sensing of such timing marks is however difficult, because the sensing devices used have to distinguish between the timing marks and the images.
• the present invention enables the use of timing marks in the spaces between the images enabling the control device to predict when an inter-image space is in the vicinity of the sensor and only to react to the timing marks at this time. In this manner, confusion between the timing marks and the images is avoided.
• the control device controls the operation of a cutting device provided at the cutting station in response to information received from the upstream and downstream measuring devices. This feature enables the sensor to be spaced from the cutting station and enables the timing marks to be positioned, if desired, at a location other than the exact point where the web is to be cut.
• the downstream web drive is stopped, and the web is stationary, while the web is being cut at the cutting station.
• a cutting knife is preferably provided at the cutting station and an associated knife transport device is provided for driving the knife across the width of the web, thereby to cut the web.
• a rotary cutting knife may be used, together with an associated knife transport device for driving the knife across the width of the web, thereby to cut the web into sheets.
• the knife transport device may comprise a movable carriage which carries the rotating cutting knife and which is supported from a continuous drive belt extending across the width of the apparatus.
• the drive belt is suitably driven by a stepping motor or by a DC motor with associated encoder.
• the carriage may be supported for movement across the width of the web by the engagement of a running wheel in a guide rail.
• the web cutting device may be adapted to cut the web in either direction of travel.
• a single knife is provided to make a single cut in the web.
• two knives operating in parallel, adapted to cut away a strip of the web material. This may be useful if it is desired to cut away, and dispose of, that inter-image portion of the web in which the timing marks have been printed. This useful effect can also be obtained with a single knife construction, by operating the knife twice, i.e. back and forth, with an intermediate advancement of the web.
• the apparatus according to the invention may be coupled to a printer capable of printing discrete images on the web, the control device being responsive to information indicative of the position of each discrete image on the web. In this manner, the apparatus is able to cut the web at desired locations, even when the size and spacing of the printed images are not constant.
• the upstream measuring device may be in the form of an encoder device associated with the upstream web drive, such as a rotational encoder which produces pulses indicative of the rotation of an upstream web drive roller.
• the downstream web drive and the downstream measuring device are preferably constituted by a stepping motor.
• Operation of the downstream web drive is preferably selected between at least three modes, namely:
• the downstream web drive is preferably controlled so as to maintain a constant position for the balance roller during the first mode.
• the second and third modes follow a predetermined profile which defines the relationship between the speed of the downstream web drive and time.
• control device is programmed to take account of a number of factors, namely:
• the parameters associated with these factors may be determined by prior calibration of the apparatus.
• the control device is preferably programmed with a correction factor, which takes account of any errors due to variations in the effective diameter of the drive rollers (the web thickness is indeed part of the effective driving diameter), slippage between the web and the drive rollers, and vibrations causing possible small encoder errors.
• This correction factor may be determined from time-to-time by comparing the expected position of a timing mark on the web with the actual position thereof or by comparing the total number of pulses received from the encoder with the total number of steps performed by the stepping motor for a period of time at the end of which the balance roller in the web buffer lies at the same balance position.
• the speed of the web is measured solely through the position sensing device of the balance roller, which provides a less accurate measurement than an encoder positioned on the upstream web drive in the short term, but a more accurate measurement in the long term.
• This arrangement provides a more accurate long term measurement, because the balance roller position integrates every error in time. Thus, even if the error between the web speed and the encoder output were to be very small, the balance roller eventually would move out of its balance position.
• the encoder on the upstream web drive is useful because it provides a more accurate measurement in the short term, when it comes to predicting the position of timing marks in the first few metres of web length.
• the encoder on the upstream web drive is also useful for calculating the correction factor to be applied by comparing the expected position of a timing mark on the web with its actual position.
• the length of the web in the buffer could be calculated from the encoder output over time, more processing time and capacity would be required compared with the direct measurement which characterises the present invention.
• a web cutting apparatus 10 is coupled to a printer 12 capable of printing discrete images 14 on a web 16 (see Figure 3).
• the apparatus comprises an upstream web drive roller 18, in contact with an opposing nip counter roller 20, driven by a motor 22 which is in turn controlled by the control system (not shown) of the printer 12.
• the web drive roller 18 continuously feeds the web 16 from the printer 12 over a freely rotating upstream guide roller 23 into a web buffer 24.
• the buffer 24 comprises a freely rotating balance roller 26 over which the web 16 passes.
• the balance roller 26 is carried on one end of an arm 30, the other end of which is pivoted about a fixed point 32.
• the balance roller 26 thereby constitutes a movable roller, the vertical position of which determines the length L b of the web path 34 in the buffer 24.
• a rotational encoder 36 is mounted on the web drive roller 18.
• the encoder 36 produces pulses indicative of the rotation of the web drive roller 18.
• the web passes from the web buffer 24 over a freely rotating downstream guide roller 25 to a downstream web drive roller 38, in contact with an opposing nip counter roller 40, driven by a stepper motor 42, is provided for intermittently feeding the web 16 from the buffer 24 to a cutting station 44.
• a cutting device 48 is provided at the cutting station 44.
• the cutting device includes a cutting knife 50 and an associated knife transport device for driving the knife 50 across the width of the web 16, thereby to cut the web 16 into sheets 76 which fall into a sheet tray 78.
• the knife transport device comprises a movable carriage 52 which carries the rotating cutting knife 50.
• the carriage 52 is supported from a continuous drive belt 80 which extends across the width of the apparatus.
• the drive belt 80 passes over a pulley 82 driven by a stepping motor 84.
• the carriage 52 is supported for movement across the width of the web by the engagement of a running wheel 86 in a guide rail 88.
• a sensor 54 is positioned between the web drive 38 and the cutting station 44 to sense timing marks 56 located on the web 16. As seen in Figure 3, the timing marks 56 are located between the discrete images 14 on the web 16, that is within the inter-image spaces 58 on the web. The timing marks 56 are spaced from each other by a distance D, which may, or may not, be constant, depending upon the nature of the images to be printed.
• a control device 28 in the form of a microprocessor, is provided to control operation of the web drive roller 38.
• the control device 28 receives pulses from the rotational encoder 36 via line 60 and signals from the sensor 54 via line 64.
• the control device 28 also receives information from the printer 12 indicative of the position of each discrete image 14 on the web 16.
• a servo potentiometer 66 sensitive to the position of the arm 30, is connected to the control device 28 by line 70.
• the control device 28 sends stepping instructions to the stepper motor 42 via line 74.
• the apparatus operates as follows.
• the web 16 is continuously fed from the printer 12 into the buffer 24 by the web drive roller 18.
• the web drive roller 18 operates at the speed of the printer which, while continuous, is not necessarily constant.
• the encoder device 36 generates pulses indicative of the operation of the web drive roller 18 and passes these pulses via line 60 to the control device 28.
• the web 16 is intermittently fed from the buffer 24 to the cutting station 44 by the web drive roller 38 driven by the stepping motor 42 in response to signals from the control device 28 via line 74.
• the web 16 is cut at the cutting station 44.
• the control device is programmed to control the stepping motor 42 of the web drive roller 38 to ensure that cutting of the web 16 at the cutting station 44 takes place at predetermined locations on the web 16.
• the control device controls the operation of the web drive roller 38 as follows.
• the control device 28 causes the web drive roller 38 to be driven at the same speed (as measured in terms of web displacement per unit time) as that of the web drive roller 18, as sensed by the servo potentiometer 66. Thereby, a constant web path length L b is maintained in the buffer 24, as indicated by solid lines in Figure 1.
• the position of the balance roller 26 is theoretically constant, at a balance position. Should any change in the web path length occur despite the web drive rollers 18 and 38 running at the same speed, perhaps due to some slippage or localised stretching of the web, the consequential upward or downward movement of the arm 30 is sensed by the servo potentiometer 66 and the control device 28 reacts to increase or decrease the speed of the web drive roller 38 in compensation. In this manner, the web buffer 24 is stabilized.
• the control device 28 is programmed for example as set out below, to calculate when the web needs to be cut. From the information received from the printer 12, the control device 28 can calculate the distance which a timing mark 56 printed on the web 16 by the printer 12 has to travel from the printer 12 before being expected to be positioned beneath the sensor 54. After feeding the calculated number of pulses to the downstream web drive motor 42 the web 16 has been advanced so that an inter-image space 58 has reached the vicinity of the sensor 54. The timing mark 56, located in this inter-image space 58 on the web 16, is sensed by the sensor 54. Signals from the sensor 54 are passed to the control device 28.
• the control device Given a constant web path distance P between the sensor 54 and the cutting station 44 and knowing the displacement of the timing marks relative to desired cutting position on the web, the control device is able to calculate how many further pulses need to be fed to the motor 42 to feed sufficient further web to the cutting station 44 in order to ensure that the web is cut at the desired position.
• the control device 28 initiates a predefined web control and cutting sequence. This may include a predefined slow-down phase for the downstream web drive motor 42 until the web drive roller 38 stops. As a consequence, the web 16 in the cutting station is then stationary. At the same moment, the control device 28 triggers operation of the cutting knife 50. The web 16 is stationary while it is being cut.
• the predefined web control and cutting sequence includes a speed up phase for the downstream web drive motor 42 to, for example, double normal speed, so as to reduce the web path length L b in the buffer 24.
• This causes the movable balance roller 26 to be pulled upwards as viewed in Figure 1, with the arm 30 pivoting about the fixed point 32.
• This upward movement of the balance roller 26 continues so long as the downstream web drive roller 38 is driven at a greater speed than the upstream web drive roller 18.
• the web control and cutting sequence then includes a slow-down phase for the downstream web drive motor 42 to normal speed. Once the normal speed is reached, the balance roller 26 ceases to rise and the web buffer 24 is again stabilized, until the next cutting operation occurs.
• the parameters L a , and L c are constant and can be determined by prior calibration of the apparatus.
• the length L b of the web in the buffer 24 is calculated from the cumulative count of the upstream encoder 36 (from the beginning of web movement) and the total number of pulses fed to the downstream drive motor 42.
• the encoder count is thereby converted into an equivalent motor step count through the use of a calibration factor which takes into account any tolerances of the mechanical components.
• the calculated length is further subjected to a correction based upon measurements of previous marker position errors, if any.
• the length L b of the web in the buffer 24 is calculated on the basis of the cumulative count of the encoder 36, the total number of pulses fed to the drive motor 42, the signal from the potentiometer 66, a timing signal from the printer 12 and previous marker position measurements.
• This process uses a calibration factor which includes the relationship between encoder and downstream motor counts for a given length of web movement, thereby including all mechanical tolerances.
• the process also uses a mathematical relationship between the balance roller position and the approximate web length in the buffer. All these signals are combined into an L b -estimation with an accuracy high enough to allow accurate cutting of a printed web without the need for timing marks.
• a slow-down profile is initiated so that the speed of the motor 42 reaches zero when all these further pulses have been fed thereto.
• a reference table is generated containing values for L b corresponding to predetermined positions of the balance roller 26.
• the length L b of the web in the buffer 24 is calculated from the cumulative count of the upstream encoder 36 and the total number of pulses fed to the downstream drive motor 42.
• the signal from the potentiometer 66 is measured and a corresponding reference value of L b is determined from the reference table.
• This reference value of L b is compared with the calculated value of L b and when appropriate a corresponding correction may be performed. This approach may obviate the need of measuring timing marks.

Landscapes

• Handling Of Sheets (AREA)
• Controlling Rewinding, Feeding, Winding, Or Abnormalities Of Webs (AREA)
• Control Of Cutting Processes (AREA)
• Nonmetal Cutting Devices (AREA)
• Controlling Sheets Or Webs (AREA)
• Advancing Webs (AREA)

Applications Claiming Priority (4)

Publications (3)

Family

ID=26315430

Family Applications (1)

Country Status (3)

Cited By (1)

Families Citing this family (12)

Family Cites Families (3)

• 2000
  • 2000-03-31 DE DE2000610171 patent/DE60010171T2/de not_active Expired - Lifetime
  • 2000-03-31 EP EP20000302774 patent/EP1044915B1/en not_active Expired - Lifetime
  • 2000-04-14 JP JP2000114338A patent/JP2000327197A/ja active Pending

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