Patent Application
20130168922
The present invention is directed to an improved apparatus and method for aligning sheets or folding carton blanks on a conveying system such as used in carton folder/gluers.
In processes involving printing on sheets of material such as paper or processing folding carton blanks, it is typically desirable that in the case of a rectangular sheet or blank that the side edges are parallel to the conveying direction and/or the leading edge is perpendicular to the conveying direction. This allows operations such as printing to be properly oriented with respect to the sheet or blank. In carton folding/gluing operations, flat sheets/carton blanks are folded along score lines and glued along a seam or at a corner, or corners, to provide a carton ready for subsequent uses such as erecting or filling. Carton folder/gluers typically include a feeder which dispenses a flat, die cut carton blank from the bottom of a stack of blanks. These feeders often do not dispense a carton blank with the desired orientation alignment because of many factors including asymmetry of carton shape and uneven weight distribution in the feeder, varying feeder belt friction coefficients, differences in feed gate settings, and other factors. Immediately after leaving the feeder, cartons are gripped by carrier belts. To create a desired spacing between each carton blank on the carrier belts, the carrier belts run faster than the feeder belts. This creates a brief ‘tug of war’ while the carton is released by the slower moving feeder belts and engaged by the faster moving carrier belts. The feeder and carrier belt positioning is often asymmetric with respect to the carton and this can cause a carton blank to twist out of the desired orientation.
Folder/gluer operators strive to make cartons feed “square,” or “aligned”, i.e., in the desired orientation with respect to the conveying direction on the carrier belts. This requires a high degree of operator skill based on years of experience.
To reduce the level of operator skill required and to better assure proper orientation regardless of machine parameters that often vary during operation, carton folder/gluers often include a carton aligner, or aligning section. In prior art aligning processes, the sheets or carton blanks have been conveyed by carrier belts with overlying balls or rollers that lightly grip the sheet or blank and laterally urge the sheet or blank against a mechanical guide comprised of an adjustable sheet metal plate with a smooth, flat surface. This section of the machinery is known as an aligning section. The loose contact between belts and angled rollers allows the sheet to shift so that it can become aligned with respect to the alignment guide bar which typically sets a side edge of a blank parallel with subsequent lower carrier belts and upper gripping belts, or rollers. This is intended to desirably align the sheet or blank for subsequent operations. Aligning sections having this general configuration are sold in Signature™ folder gluers sold by American International Machinery of Oak Creek, Wis. and folder gluers made by Bobst Group SA of Lausanne, Switzerland, and others.
As another example, U.S. Pat. No. 6,162,157 to Morisod shows an alignment device that, while using a traditional guide bar 100, uses air flow to lightly contact blanks of “low specific gravity”, partly folded blanks and other delicate blanks against an angled belt which otherwise traditionally directs the blank against the guide bar.
There are some drawbacks to the prior art method of aligning flat sheets or carton blanks including:
There are some subsequent processes such as applying adhesive with systems provided by Nordson of Westlake, Ohio, or windowing systems such as provided by Tamarack Products of Wauconda, Ill., that require the speed and position of the blank to be known so that subsequent speed and position can be accurately predicted. For example, the Tamarack® Vista® windowing machine uses a scanner approximately two feet ahead of the Vista windower to sense carton position. Carton speed is indirectly sensed by an encoder that measures the speed of a lower carrier belt. During aligning, substantial slippage occurs between the sheet or carton blank and the carrier belts in the aligning section, preventing proper sensing of sheet/carton speed and accurate prediction determination of the sheet/carton's subsequent position with the result that the window application position will not be accurate. For these applications, the sheet/carton blank must be sensed later in the process, after aligning. This necessitates scanning of the blank later in the folder/gluer and can result in an undesirable or impractical location for the windower unit.
The instant invention relates to a new method and apparatus for aligning sheets or folding carton blanks. Two laterally separated scanners each sense a respective portion of the lead edge of a blank. The signals from the scanners are fed to a processor which evaluates the timing difference (or the difference in master encoder or virtual master pulses) between each scanner's signal. Two sets of grippers engage each sheet or blank adjacent its side edges. The grippers are capable of operating at different speeds via a differential drive or electronically controlled servo drives. Differing speeds are commanded at each gripper in order to steer or rotate the blank relative to subsequent carrier belts. Suitable servo control systems for these steps of operation are manufactured by Bosch Rexroth of Lohr am Main in Germany.
The alignment of the blank can be adjusted in a over a shorter distance than prior art approaches and its average velocity can be adjusted to be very close to its velocity on subsequent carrier belts—allowing for a more compact folder/gluer and more freedom in locating a windower unit.
Steering the blank is no longer determined by a side edge of the blank riding against a mechanical guide, so side edge length and possible irregularities in the side edge are no longer a concern.
A non-rectangular sheet/blank can be aligned as desired and a leading edge with irregularities such as tabs, angles, or cut-out portions can all be accommodated to provide highly accurate sheet/blank positioning and orientation.
The appended claims set forth those novel features which characterize the invention. However, the invention itself, as well as further objects and advantages thereof, will best be understood by reference to the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, where like reference characters identify like elements throughout the various figures, in which:
a, 1b, 1c represent a progression of schematic top views of a prior art apparatus and method for aligning folding cartons;
a, 4b, 4c, and 4d illustrate a progression of top views of the inventive apparatus and method for squaring the lead edge of a carton blank;
a and 1b show a top view schematic of a prior art carton aligner used with prior art carton folder/gluers such as those provided by American International Machinery of Oak Creek, Wis., Bobst of Lausanne, Switzerland and Heidelberger Druckmaschinen AG of Heidelberg, Germany. Carton blank 11, shown here in a skewed orientation relative to its intended conveying direction D, is carried on driven carrier belt 12. Carrier belt 12 is typically driven by drive pulleys on a drive shaft via a motor drive system (not shown). In
b shows a subsequent moment in time in relation to
c illustrates a still later moment in time. Carton blank 11 has rotated further clockwise and has come into contact with aligning edge 13a so that the carton blank is now traveling parallel to aligning edge 13a, which is typically also parallel with side frames 16a and 16b. Edge 13a defines the desired carton 11 conveying direction D. Edge 13a also defines the lateral position of carton edge 11a relative to side frames 16a, 16b so that subsequent operations, such as folding at various scores, window application, labeling, die cutting, and other operations known in the art (but not shown here), can be performed at the desired lateral locations on carton blank 11.
Powered upper gripper assembly 33 can be driven in a variety of ways. In a preferred embodiment, a servo motor 33m, such as provided by Bosch Rexroth of Lohr am Main, Germany drives gripper 33 directly. The servo motor 33m is controlled precisely by a Bosch Rexroth control system and programmed with Visual Motion software also supplied by Bosch Rexroth, and programmed by the user. Additional disclosure of the servo control system is provided in the aforementioned references U.S. Pat. Nos. 6,772,663 and 7,901,533. To reduce cost, a stepper motor could be substituted, or a mechanical drive via belts, pulleys, gears, etc., from the folder/gluer drive could drive gripper 33 via a differential gearbox such as provided by Tandler of Bremen, Germany or Harmonic Drives of Peabody, Mass. Drive gripper 33 drives opposing roller 34 when carton blank 11 is not present therebetween. When carton blank 11 is gripped between drive roller 33 and opposing roller 34, drive roller 33 drives carton blank 11 and, in turn, carton blank 11 drives opposing roller 34.
In normal operation, i.e., when no corrective action is being performed on the orientation of carton blank 11, drive roller 33 and vacuum belt 35b will have identical outer perimeter speeds and the carton blank 11 will be conveyed in the direction D and in the same orientation as it was received into engagement between gripper assembly 32 and drive belt 35b and between gripper assembly 33 and gripper assembly 34.
Vacuum belt module 31 is driven by the machine drive (not shown), typically an AC or DC variable speed motor drive, as commanded by the operator's speed input to a graphical user interface such as provided by Exor of Torino, Italy or other known means of operator interface such as speed up/down pushbuttons or speed control dials. Opposing gripper assembly 32 is then driven by the vacuum belts when carton blank 11 is not gripped between belt 35b and gripper assembly 32. When carton blank 11 is gripped between belt 35b and gripper assembly 32, belt 35b drives carton 11 and, in turn, carton 11 drives gripper assembly 32.
Scanners 36a and 36b, such as provided by Keyence of Osaka, Japan, are used to sense the position of the lead edge, or other scannable feature, of carton blank 11. Presuming that the lead edge of carton blank 11 is perpendicular to the desired direction of travel D, then scanners 36a and 36b will sense the carton blank's lead edge at the same time. If the carton blank 11 is skewed, scanners 36a and 36b will sense the leading edge at different points in time.
Signals from the scanners 36a, 36b are fed as inputs to a servo controller (not shown), such as a Bosch Rexroth PPC. In cases where the inventive carton aligner is used in conjunction with a Tamarack Vista window applicator, the PPC and graphical user interface, or touchscreen, will already be in place for the Vista windower and readily accepts these additional inputs. The general operation of the servo control system is disclosed in U.S. Pat. Nos. 6,772,663 and 7,901,533, already referenced. In a preferred embodiment, the scanners are located ahead of the gripper assemblies 32, 33, and 34. The advantage of this positioning is that the carton blank 11 will be firmly gripped by and under control of the gripper assemblies 32, 33, 34 and vacuum belt 35b, assuring accurate control and performance of the aligning process.
In a simplified mode of operation, if scanners 36a, 36b sense the carton blank 11 lead edge at the same time, the blank 11 is aligned square with the direction of motion D and no corrective action is needed. The servo system commands the servo motor to rotate upper gripper assembly 33 so that its outer peripheral speed matches the speed of vacuum belt 35b.
If scanner 36a senses the carton lead edge before sensor 36b, the time (or number of encoder pulses) difference is noted by the servo control system and the servo motor 33m is commanded to temporarily slow down. This causes the carton blank 11 to rotate slightly clockwise when viewed from the top, swinging the carton into the desired alignment. The pivot points of the rotation will be located essentially under gripper assembly 32.
If the opposite case occurs, i.e., scanner 36a senses the carton lead edge after sensor 36b, then servo motor 33m is temporarily commanded to speed up.
In a simplified embodiment as shown in
In
In
A commanded average speed increase at gripper assembly 33 during a programmed time interval (or number of encoder pulses), will cause a corresponding incremental realignment of the carton blank's leading edge. For example, if the control system detects the speed of the carton blank, e.g., 300 ft/min or 60 inches/second, and after evaluating scanner 36a and 36b signals triggered by the lead edge of the blank, determines that the edge passing under scanner 36a is 2 milliseconds later than the edge passing under scanner 36b, the control system calculates a speed adjustment and time duration factor, typically within preset parameter limits, to correct the 1 millisecond or 0.120″ alignment error (60 inches/sec×0.002 sec=0.120″). If the programmed speed increase of gripper assembly 33 was chosen at 2 inches/second (from 60 inches/second to an average of 62 inches/second) the increased speed would be required for 60 milliseconds (2 inches/sec×0.060 sec=0.120″). This presumes the use of a responsive servo system capable of rapid speed changes. The Vista window applicator regularly accelerates from 0 to 88 inches/second and back to zero in about 90 ms or about 2000 in/sec/sec. In comparison, the above correction move represents about 4000 in/sec/sec. However, the load inertia of the aligner gripper assembly 33 and opposing gripper assembly 34 is about 1/10th that accelerated by the proven Vista applicator and within the capabilities of the servo system.
The speed increase is continued for an amount of time calculated by the control system sufficient to rotate carton blank 11 to the desired orientation, typically so that the leading edge of carton blank 11 is perpendicular to the folder/gluer's conveying direction D, as illustrated in
Scanners 36a, 36b are typically adjustable via sliding mounts that allow the scanners to be adjusted longitudinally (in the direction of motion of the carton blanks) or laterally (perpendicular to the direction of motion).
Longitudinal adjustment allows the two scanners 36a, 36b to sense the edge of two non-aligned edges simultaneously. For example, this latter scanner arrangement would be desirable when the carton blank 11 is not a simple rectangle, but rather has typical end flaps with varying lengths, or when it is desired to intentionally deliver carton blanks with the lead edge not square to the direction of motion, i.e., angled.
Lateral adjustment is desirable to accommodate varying carton shapes, especially cartons with die cut window openings, so that the gripper may grip along the length of a carton without interruptions while each scanner is laterally positioned to sense a desired lead feature of the carton blank.
If the scanners 36a, 36b are not in line with their respective grippers, the correction calculations are slightly more complicated, but are readily entered and accommodated via the graphical user interface and programming for the servo system. An illustration on the graphical user interface (such as a touchscreen) similar to
In other embodiments, the vacuum belt module 31 may be replaced by a roller or traditional folder/gluer carrier belt assembly in combination with gripper assembly 32 in known ways. Alternatively, gripper roller 32 may be driven by another servo motor (not shown), such as a counterpart to motor 33m or by other types of motors suitable for providing a coordinated speed differential between gripper assembly 32 and gripper assembly 33. In another embodiment, a differential gear box may be provided between gripper assemblies 32 and 33 which can also provide a coordinated speed differential between gripper assemblies 32 and 33.
The foregoing disclosure provides a means of aligning, or squaring, the leading edge of a carton blank with the desired direction of conveying. It does not, however, provide a means for registering, or locating, a side edge of the carton-blank in the desired lateral position relative to the side frames of the carton folder/gluer so that a longitudinal fold will occur along a pre-scored line, or so that a window patch is applied square to the carton blank and in the desired lateral location on the carton blank.
It is also desirable to minimize the number of sensors needed to provide inputs to the squaring and lateral aligning process. This helps reduce the:
The next described embodiment of the invention, which is illustrated schematically in
In
Signals from an additional scanner 37 are provided as inputs to the servo controller system. Scanner 37 is known in the art as an analog gap sensor consisting of a glass bifurcated light guide and an analog output photoelectric sensor, such as provided by Tri-Tronics® of Tampa, Fla. The analog gap sensor has a sensing zone 37z up to about 1.5″ wide. A variable analog output, typically 0-10 volts, is governed by how much of the sensing zone is covered by the carton blank 11. Scanner 37 position is typically adjusted so that one-half of sensing zone 37z is covered by the carton blank 11 when the carton blank edge E is in the desired lateral position relative to target line T. When one half of the sensing zone is covered, servo gripper assembly 33 is driven at a speed 33v that matches the speed 32v of gripper assembly 32.
Scanner 37 is shown in a location upstream, or behind, the rotational axis of the gripper assemblies 32, 33 to provide a means of sensing not only carton position, but also a means of sensing the correctional efforts of the servo driven gripper assembly 33 speed adjustments relative to gripper assembly 32. Scanner 37 could be located ahead of the grippers' rotational axes, but the controlling techniques would need to be effectively reversed from the detailed description that follows. The amount of offset OS could be varied by the designer, or user, as desired. However, the correctional algorithm would need parametric adjustments to obtain the desired corrective action.
In a further simplified embodiment, scanner 36b could be eliminated by using scanner 37 to provide the initiation of the squaring and aligning operation as well as providing subsequent inputs to the controller for the squaring and alignment process.
In the case of
When these corrective actions are incremental and interposed within a short amount of time where 33v is commanded to match 32v, and if necessary, repeated, the carton edge E not only becomes parallel to target line T, but the carton edge also comes into lateral registration, or coincides, with the target line T.
This sequential positioning correction is illustrated in
In pos. 2, the carton blank 11 has over-rotated as compared to Pos. 1. But this can be desirable in bringing the side edge E into the desired lateral position. In pos. 2, servo gripper assembly 33 is commanded to match the speed of gripper assembly 32. The matched speed mode may be for a predetermined amount of time/distance or it may instead rely on scanner 37 to indicate that carton edge has covered half, or more, of scanning zone 37z. This has the effect of driving the carton slightly laterally to the right relative to gripper assemblies 32, 33. If the carton has become aligned, as sensed by a constant covered scanner sensing zone 37z, then servo gripper assembly 33 continues to match gripper 32 assembly speed. If sensing zone 37z becomes more than half covered, as shown in Pos. 3, gripper assembly 33 is commanded to exceed the speed of gripper assembly 32 and this has the effect of rotating the carton blank 11 counterclockwise until scanning zone 37z is halfway covered again at which time gripper assembly 33 is commanded to again match gripper assembly 32 speed.
These corrective moves will continue until carton blank edge E is aligned with and parallel to target line T and scanning zone 37z is one half covered by carton blank 11, at which time gripper assembly 32 and 33 speeds match and remain matched so long as one-half of scanner zone 37z remains covered. Pos. 4 shows a subsequent position of carton blank 11, where it is aligned with and has one of its edges coincident with target line T as desired and no longer is under the influence of the aligning process for conveyance along a carton folder/gluer for further operations such as windowing, prebreaking, backfolding, and final folding.
In the foregoing discussion, a rectangular carton blank has been disclosed to simplify the description of the inventive method and apparatus. Typically, however, folding cartons, while often generally rectangular in shape, have many die cut facets and features that complicate the practice of the invention.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the relevant arts that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications that fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
This application claims priority pursuant to 35 U.S.C. 119(e) from U.S. Provisional Application Ser. No. 61/581,505 filed Dec. 29, 2011.
| Number | Date | Country | |
|---|---|---|---|
| 61581505 | Dec 2011 | US |
