The present invention relates generally to the input portion of a high speed inserter system in which individual sheets are cut from a continuous web of printed paper for use in mass-production of mail pieces.
Inserter systems, such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. of Stamford, Conn.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
The input stages of a typical inserter system are depicted in
The separated documents must subsequently be grouped into collations corresponding to the multi-page documents to be included in individual mail pieces. This gathering of related document pages occurs in the accumulator module 40 where individual pages are stacked on top of one another. The control system for the inserter senses markings on the individual pages to determine what pages are to be collated together in the accumulator module 40.
Downstream of the accumulator 40, a folder 50 typically folds the accumulation of documents, so that they will fit in the desired envelopes. To allow the same inserter system to be used with different sized mailings, the folder 50 can typically be adjusted to make different sized folds on different sized paper. As a result, an inserter system must be capable of handling different lengths of accumulated and folded documents. Downstream of the folder 50, a buffer transport 60 transports and stores accumulated and folded documents in series in preparation for transferring the documents to the synchronous inserter chassis 70.
In a typical embodiment of a web cutter 20, the guillotine cutter arrangement requires that the web be stopped during the cutting process. As a result, the web cutter 20 transports the web in a sharp starting and stopping fashion and subjects the web to high accelerations and decelerations.
With the guillotine cutter arrangement, the web feeder 10 may typically include a loop control module to provide a loop of slack web to be fed into the web cutter 20. During high speed operation, the accelerations experienced by the web in the slack loop can be quite severe. The inertia experienced by the web from the sudden starting and stopping may cause it to tear or become damaged.
Sensors 12 and 13 scan a mark or code printed on the web. The mark or code identify which mail piece that particular portion of web belongs to, and provides instructions for processing and assembling the mail pieces. In addition to using the scanned information for providing assembling instructions, the scanning process is useful for tracking the documents' progress through the mail piece assembly process. Once the location of a document is known based on a sensor reading, the document's position may be tracked throughout the system by monitoring the displacement of the transport system. In particular, encoders may be incorporated in the transport systems to give a reliable measurement of displacements that have occurred since a document was at a certain location.
After the web 120 has been split into at least two portions, the web is then cut into individual sheets by cutter 21. The cut is made across the web, transverse to the direction of transport. Downstream of the cutter 21 the individual cut sheets are transported by nips 23. Nips 24 further serve to transport the sheets to the right angle turn 30 portion of the system.
Right angle turn devices 30 are known in the art and will not be described in detail here. However, and exemplary right angle turn will comprise turn bars 32 and 33. Of the two paper paths formed by the right angle turn 30, turn bar 33 forms an inner paper path for transporting sheet 1. Turn bar 32 forms a longer outer paper path on which sheet 2 travels.
Because sheets 1 have a shorter path through the right angle turn 30, a lead edge of sheet 1 will be in front of a lead edge of sheet 2 downstream of the right angle turn 30. Also, the turn bars 32 and 33 are arranged such that sheet 2 will lay on top of sheet 1 downstream of the right angle turn, thus forming a shingled arrangement. Downstream of the right angle turn 30, further sets of roller nips 36 transport the shingled arrangement of sheets.
In a feed cycle, the paper is advanced past the blade of the guillotine cutter 21 by a distance equal to the length of the cut sheet and is stopped. In a cut cycle, the blade 21 lowers to shear off the sheet of paper, and then withdraws from the paper. As soon as the blade 21 withdraws from the paper path, the next feed cycle begins. The feed and cut cycles are carried out in such an alternate fashion over the entire operation.
In some web cutters, it is desirable to achieve a cutting rate of 25,000 cuts per hour or more, for example. This means that the web cutter has a feed/cut cycle of 144 ms. Typically the length of the cut sheet is 11 inches (27.94 cm). If the time to complete a cut cycle is about 34 ms, then the total time in a feed cycle is 110 ms. This means that the web must be accelerated from a stop position to a predetermined velocity and then decelerated in order to stop again within 110 ms. As guillotine cutters are required to generate pages even faster (up to 36,000 cuts per hour), precise motion control coordinated over various mechanisms must be implemented in order to eliminate web breakage and to reliably cut sheets of proper length at high rates to provide to downstream devices.
The present invention provides a high speed input system for an inserter machine that is capable of faster, more accurate, and more reliable high speed cutting. In particular, the manner of controlling the guillotine cutter, the cutter transport, and an upstream web handler transport provide a novel way to increase throughput for mail production. The system in accordance with the present invention is used for separating individual sheets from a continuous web for creating mail pieces in an inserter machine. A first component of the system is a guillotine cutter blade arranged to cyclically lower and raise to transversely cut the web transported below the cutter blade. A cutter transport is arranged to cyclically feed and stop the web in a path below the cutter blade for cutting by the cutter blade. A web handler transport is positioned upstream of the cutter transports and provides web to the cutter transport at lower peak velocities and accelerations than are experienced by the web at the cutter transport. The web handler transport includes a loop forming arrangement to act as a buffer between the drastic motion changes of the cutter transport and the steadier movement of the web handler transport.
The system is controlled to maximize throughput with a controller. The controller is programmed to control the high speed input module in accordance with a repeating cycle. The cycles have cycle times that can vary in length. The cycle time is determined as an amount of time between a first web feed request and an earliest possible time that a subsequent second web feed request can be acted upon. At the beginning of each cycle, the controller controls the system in accordance with predetermined motion control profiles for the various components.
In particular, a cutter transport motion control profile initiates feeding of a document length of web after receiving the first feed request. Under this profile, the cutter transport stops after the document length of web has been fed.
A cutter motion control profile causes the cutter blade to begin descending when the cutter transport has moved the web a trigger distance, less than the document length, and while the web is still moving. The trigger distance is calculated such that the cutter blade will first make contact with the web as soon as it has been halted by the cutter transport motion profile. The cutter blade is raised back to its initial position after having completed its cutting of the web. Also, the cutter transport motion control profile begins moving the web in response to a second feed request, for a subsequent cycle, as soon as the cutter blade rises above a horizontal level of the web, and not waiting until the cutter blade is at a resting position above the web.
A web handler transport motion control profile is also initiated during each cycle. The web handler transport profile moves the web the document length at velocities and accelerations less than the velocities and accelerations of the cutter transport. At the end of the cycle, the web handler transport causes the web to be transported at a nominal velocity selected to maintain an appropriate amount of the web loop in the web handler. The loop expands and contracts as the downstream cutter transport stops and starts as the cutter blade cuts the web in each cycle.
In a preferred embodiment, the cutter transport motion control profile is comprised of a constant acceleration for half of the document length and a constant deceleration for the other half of the document length. Similarly, it is preferred that the web handler transport motion control profile comprises steady motion at the nominal velocity in steady state operation. In a non-steady state embodiment, if no feed request is present at the end of the cycle, the web handler transport motion control profile decelerates the web at a constant deceleration until the web comes to a stop, or until a subsequent feed request is received.
Preferably, the web handler transport motion control profile also includes an intercept algorithm that is employed at the beginning of each cycle. The intercept algorithm calculates the appropriate web handler transport motion control profile to accomplish a displacement of the document length within the cycle time starting at a current velocity and ending at the nominal velocity. In a further preferred embodiment, the intercept algorithm calculates the web handler transport motion control profile as a constant acceleration and a constant deceleration during the cycle.
Also in the preferred embodiment, the cutter blade is coupled by a cutter arm to a rotary motor. One full rotation of the rotary motor corresponds to one complete down and up movement of the cutter blade. The cutter blade motion control profile may be comprised of a constant rotary acceleration for a first half of the rotation while the cutter blade is descending and a constant deceleration for a second half of the rotation while the cutter blade is ascending.
In a further embodiment, the controller includes a start-up profile for handling the web as it is first installed into the high speed input module. The start-up profile controls the cutter transport and the web handler transport to bring a lead edge of the web to a first cut location. The web handler is further controlled to execute a nominal loop displacement. The nominal loop displacement is a function of a differential displacement between the cutter transport and the web handler transport during a portion of the cycle while the cutter transport operates at a higher velocity than the web handler transport. Thus, the appropriate quantity of loop is provided for the system to begin steady-state operation.
In the preferred embodiment, the system operates on a web having a 2-up sheet configuration having sheets side-by-side on the web. To separate the side-by-side sheets, the system includes a center cutting device positioned upstream of the guillotine cutter. The center cutting device splits the side-by-side portions of the web prior to cutting by the guillotine blade.
Further details of the present invention are provided in the accompanying drawings, detailed description, and claims.
a and 3b depict a preferred arrangement of the cutter transport and the web handling transport.
a, 4b, and 4c depict a view of a guillotine cutter blade cutting across a sheet of web in varying stages.
A previously filed patent application titled METHOD AND DEVICE FOR REDUCING WEB BREAKAGE IN A WEB CUTTER, U.S. patent application Ser. No. 10/431,237 (Attorney Docket F-616) includes descriptions of components related to the present invention, and that application is hereby expressly incorporated by reference in its entirety.
A preferred embodiment for arrangement of the components of the high speed web input system is illustrated in
In particular, when the cutter transport 90 moves the web in a direction substantially in a horizontal plane, the web handler transport 80 is oriented such that it moves the web in a direction substantially in a vertical plane. As such, the web is pushed upward when it enters the loop 180. As shown in
It is preferred that the control loop 180 be small so as to reduce the inertia acting on the web. In order to achieve a small control loop 180, both the cutter transport 90 and the web handler transport 80 are set in motion in a coordinated way. In particular, both the cutter transport 90 and the web handler transport 80 are designed to accelerate and decelerated in a related operation cycle. Because only the cutter transport 90 must stop to allow for the cutting cycle, the web handler transport 80 can accelerate and decelerate differently from the cutter transport 90. Thus, while the cutter transport 90 operates at full acceleration and advances the web 120 as quickly as possible, the web handler transport 80 operates at a lower acceleration rate. This lower acceleration rate reduces the breakage of the web as the web paper is pulled by the web handler transport 80 from the upstream source. At the same time, because the paper at the control loop 180 is moved by the web handler transport 80 toward the cutter transport 90, the stop-and-start motion of the cutter transport 90 does not produce as severe a pull on the paper.
a-4c depict the guillotine cutter 21 through a downward cutting motion, starting at a beginning position in 4a, to a finished cut position in 4c. Guillotine cutter blade 21 preferably has an edge that is vertically inclined at an angle above the path of web 120. As the blade 21 is lowered (
It will be understood by those skilled in the art that motor 22 may also be coupled to the crank 25 through a coupling ratio other than unity. Thus a complete 360 degree cutting cycle may actually correspond to more or less than a full rotation of a motor, or even multiple rotations. Accordingly, the term “rotary motor” in this application shall be understood to mean the motor and any corresponding coupling that results in movement of the crank 25.
Positions A-H of the rotary motor 22 in
To facilitate description of the proposed control method, this description assumes a guillotine cutter system 1 that executes an ‘Advance then Cut’ sequence triggered by a feed request 64. A feed request 64 is a command from the system controller to provide a next sheet for cutting and processing. Feed requests 64 will typically be received by the system periodically, but there may be pauses between feed requests 64 as downstream conditions indicate that the devices there are not ready to receive more sheets. One of skill in the art will understand that the control method described herein is adaptable for a ‘Cut then Advance’ sequence triggered by a Feed Request 64.
The present invention provides for precise displacement-based motion for cutter transport 90, blade motor 22 and web-handler transport 80 axes for a guillotine cutter system 1. For steady state operation, i.e. where a feed request 64 is always present, both the cutter transport 90 and blade motors follow triangular velocity profiles and the web-handler 80 motor follows a constant velocity profile.
If practical velocity limitations emerge for the cutter transport profile 61 or blade motion profile 63 (i.e. paper handling, scanning or motor/drive constraints), other profile types such as trapezoidal profiles can be substituted, however use of the triangular waveform minimizes accelerations for a given cut rate performance. Also, nominal web-handler motions 62 could be made more complex than constant velocity, i.e. periodic trapezoidal or sinusoidal profiles could be used. These more complex profiles may provide some incremental improvement for web control. However, constant velocity motion will significantly reduce the accelerations and forces as seen by the web and is the most straightforward motion to implement when the complexities of stopping and starting conditions are taken into consideration.
In the preferred embodiment, the driving parameter that determines the cut generation rate of the system is Cycle Time as illustrated in
By way of example, motors and coupling ratios preferably accommodate a 36K cut/hr performance goal (72 K sheets/hr in 2-up mode) while generating 11 inch cut sheets. 36 K cut/hr equates to a minimum allowable cycle time of 100 ms. The commanded speed ratio parameter, k, is defined as the minimum allowable cycle time divided by the desired commanded cycle time where 0<=k<=1. Therefore, for 11 inch cut sheets when consecutive feed requests 64 are generated periodically every 100 ms, the corresponding speed ratio is 100%. The system rate is effectively controlled by changing the value of the speed ratio parameter. Since this parameter drives the Cycle Time, it can be changed to any value between 0 and 1 (100%) per cycle but also only takes effect at cycle boundaries.
Maximum accelerations and decelerations for the cutter transport 90, blade 21 and web-handler transport 80 axes are pre-determined based on the 36 K, 11 inch sheet condition in conjunction with predetermined motion overlap displacements between cutter transport 90 and blade 21 resulting from geometrical constraints and actual servo motion tolerances (includes accuracy and settle time). These same maximum acceleration and decelerations are used when cutting longer and shorter sheets, thereby resulting in lower and higher maximum cut sheet generation rates, respectively.
Motion profiles, as depicted in
As seen in
(In the following equations the term “tractor” refers to the preferred embodiment of cutter transport 90.)
As previously mentioned, if practical considerations warrant, this cutter transport profile 61 could also be a trapezoidal profile. For this case, an additional variable must be added to the above equations to limit the maximum velocity.
The blade profile 63 is a triangular velocity motion profile executing a 360-degree displacement move that begins when the cutter transport 90 has reached a pre-calculated displacement. The blade profile 63 is computed based on the speed rate, maximum blade acceleration and maximum blade deceleration according to the following equations:
The blade 21 begins its motion profile 63 when the displacement of the cutter transport 90 is such that after the blade 21 has reached displacement, A (see
The web handler profile 62 is computed based on a positional move relative to the desired position of the web-handler transport 80 at the most previous cycle boundary. The final position is the desired position of the web-handler transport 80 at the most previous cycle boundary plus the cut sheet length. The initial velocity of the displacement move is the current desired velocity and the final velocity is the nominal desired web velocity, Vweb_nom.
An intercept algorithm is used to calculate the necessary motion profile 62 to accomplish this displacement in a time equal to the current value of Cycle Time using the initial and final desired velocities. Details of one possible algorithm are described in more detail below.
If a feed request 64 is not present at the end of a Cycle Time (i.e. a cycle boundary), the web-handler 80 will begin an immediate deceleration equal to Dweb. If the time from the cycle boundary to the next feed request 64 is sufficiently long, the web-handler 80 will come to rest. Velocities and accelerations for the web-handler 80 are defined as follows:
When the web-handler 80 does decelerate to rest, the resulting deceleration displacement is equal to Xloopstop. Xloopstop is the additional displacement added to the control loop 180 between the web-handler 80 and cutter transport 90 during a stopping condition and is computed as follows:
Since the velocities and accelerations are appropriately scaled, when the web-handler 80 does go to rest due to the absence of a feed request 64, the value of Xloopstop is a constant regardless of the value of the speed ratio, k, for any given cycle.
By virtue of the displacement move being referenced to the desired position of the web-handler 80 at the last cycle boundary, the web-handler 80 will resynchronize itself at every cycle boundary, even if a feed request 64 is received during or after a deceleration to rest.
The system also includes a routine for initial paper loading and startup. The blade mechanism 21 is homed such that its crankshaft 25 resides at TDC of the stroke. During the web loading all motors are deactivated for operator safety. The web 120 is installed into the cutter transport 90 with the lead edge of the web 120 upstream of the sensors 12 and 13. Then the web 120 is installed into the web-handler 80 tractors and the web 120 is pulled tight by manually moving the web-handler 80 tractors without deforming the holes in the paper. The cover is closed and all three devices 22, 80, and 90 are activated to servo in place. Next the blade 21 mechanism is homed to TDC (top dead center). Next both cutter transport 90 and web-handler 80 motors execute a displacement move together to bring the lead edge to the cut location.
Next the web-handler 80 executes a displacement move equal to (Xloopnom+Xloopextra). Xloopnom is a calculated loop 180 displacement required at the start of the cutter transport profile 61 to ensure that the loop 180 size always remains a positive value during steady state operation. This displacement is calculated based on the smallest loop size condition, which occurs at the instant that the cutter transport velocity profile 61 falls below the web-handler velocity profile 62 during cutter transport 90 deceleration and is calculated as follows:
Xloopnom=Xtractor—accel+Xdecel−Xweb
where:
Xloopextra is a design parameter that adds margin on the initial loop 180 size to ensure that the loop 180 size never gets close to zero during operation or to generally increase loop 180 size if a reliability benefit is realized from such. For example, this value can be about ½ inch. Therefore the actual initial loop 180 size before starting a cutter transport profile 61 is (Xloopnom+Xloopextra). Once this (Xloopnom+Xloopextra) displacement move is completed, the loading sequence is complete and the cutter 21 is now ready to execute full speed operation or operation at any speed ratio, k, upon receipt of a feed request 64. Recalling from previous discussion, in the absence of a feed request 64, the loop 180 size will increase further by displacement, Xloopstop.
The resulting total loop 180 size during a stopping condition is therefore:
Xlooptotal=(Xloopstop+Xloopnom+Xloopextra)
The following are exemplary parameters for the above equations for a preferred embodiment of the system for performing 36,000 cuts per hour:
For job parameter:
As described above in connection with web handler profile 62, an intercept algorithm is used to define the velocity of the web handler transport 80 as a function of time from an initial velocity to a final velocity over a fixed time period with the axis experiencing a fixed displacement. The following is a preferred embodiment of the intercept algorithm, although it will be understood by one of ordinary skill in the art that other intercept algorithms may be used. Given:
vi=initial velocity
vf=final velocity
tx=time for the profile to execute
dx=displacement incurred during the profile
The intercept algorithm determines an acceleration that may be applied from vi to an intermediate vm and then reversed (multiplied by −1.0), and applied from vm to the given vf The intercept algorithm calculates the values for a (the acceleration) and vm without bound.
t1=time at which the changing velocity reaches vf the 1st time
t2 time to accelerate from vi to vm
Let d1 be the displacement from t0 to t2.
Let d2 be the displacement from t2 to tx
Therefore:
dx=d1+d2
The expressions d1 and d2 may be expressed in terms of vm,vi,vf, and a.
So dx in terms of vm,vi,vf and a results in the equation:
Solving for vm:
Solve for a . . . call this equation 1
Referring to the velocity graph of
The similar triangles gives us
Substituting t2 from the previous equation results in:
And solve for t1
Now using the equation:
vf=vi+αt1
and substitute what we concluded about t1 previously:
and solve for α . . . call this equation 2
Using, equation 1 and equation 2 here are both expressions for the acceleration derived
from different approaches . . . and they must be equal
So now we have an equation with one unknown . . . vm
Solving for vm:
Once vm is determined, use equation 2 to solve for a
Test the results produced by both roots (plus or minus 2 times the radical) . . . one will be correct.
The following is exemplary embodiment of the intercept algorithm in computer code:
Throughout this application the preferred web moving mechanisms have been described as tractors. However, it is also possible to use wheels and rollers to move the web. This is known in the industry as pinless tractors. With wheels and rollers, it is not necessary to provide sprocket holes of the web.
Although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.