Automated web chop-out control for cut-to-mark cut-off machine

Abstract

A moving web is divisible into a leader having a first set of registration marks and a trailer having a second set of registration marks. At a transition between the first and second sets of registration marks, a target is applied adjacent the initial mark of the second set. The target is sensed and tracked electronically to a shear. During an order change or a roll-to-roll change within an order, the web is automatically severed transversely by the shear two or more times to chop out a portion of the leader and trailer including the transition between the sets of marks. The leading edge of the trailer is tracked to a station intermediate the shear and the cut-off machine. The cut-off machine knives "crop" cut the trailer at the first registration mark following the leading edge of the trailer and thereafter cut the trailer automatically into blanks in synchronization with the second set of marks. Operation of the cut-off machine knives in the cut-to-mark mode is maintained without loss of synchronization across the portion of the web chopped out by the shear. Operator intervention is eliminated, and scrap is minimized.

Description

BACKGROUND OF THE INVENTION

The invention is related to the automation of direct drive cut-off machine having cut-to-mark control. A direct drive cut-off machine is one in which the cyclic speeds of the cut-off knives are electronically controlled. The knives cut a continuous web of pre-printed corrugated board at or in reference to registration marks to form sheets or "blanks" of the desired length.

In particular, this invention is related to the control of such knives to effect automatic web chop-out as part of an order change or roll-to-roll change together with automatic synchronization of the knives to the registration marks following the portion of the web chopped out.

The knives are slaved to an optical sensor, which detects presence or absence of the registration marks, and a logic control which synchronizes the knives to the registration marks so as to cut the web at or in specific relation to the registration marks. The logic control periodically enables the optical sensor to scan a narrow portion of the web edge for a registration mark over a short period of time known in the art as a "window". The "window" is intended to prevent the optical sensor from producing spurious signals caused by pre-printed material or blemishes on the web which might otherwise be mistakenly identified as a registration mark.

Heretofore, operating in the cut-to-mark mode, intervention by an operator was necessary when the web was formed of one or more webs connected by a splice and either (1) a roll-to-roll change had occurred within an order wherein the spacing between registrations marks was preserved on both sides of the splice but the spacing between marks was lost across the splice, or (2) an order change was required wherein the spacing between registration marks changed from one order to another across the splice, requiring the cut-off knives to cut sheets of different lengths on each side of the splice.

Operator intervention is necessitated when there has been an order change or a roll-to-roll change within an order because the cut-off knives will normally not be in synchronization with the registration marks of the web following the splice. The registration marks following the splice do not appear in the optical sensor "windows" generated by the logic control since the "windows" are generated based on the spacing between marks preceding the splice. The operator must depress an upstream or downstream adjust button to cause the logic control to synchronize the knives to the registration marks on the web following the splice. This manual adjustment is time consuming and results in the temporary cutting of sheets of improper length, producing scrap and an exceptionally long sheet which may obstruct the sheet-stacking mechanism.

In addition, for an order change it is necessary to sever the web at the splice to separate the old and new orders, and for a roll-to-roll change it is necessary to sever the web at the splice to permit the cut-off knives enough time to "cock" in preparation for the first cut of the new roll web. Severance of the web must be initiated manually. The operator observes the splice as it approaches the shear and presses a button to fire a shear control which causes the shear knives to sever the web into a leader and trailer. Typically, a splice is missed by several feet using this technique, resulting in wasted board.

The trailer has a tapered edge at the area of the splice where there is a change in width between the webs. The edge taper may be accompanied by a poor taper in the glue applied to the trailer. It is desirable to chop out the edge and glue taper together with the splice.

The present invention obviates (1) an operator-initiated upstream or downstream adjust for an order change or a roll-to-roll change, and (2) manual-initiated firing of the shear, in the cut-to-mark mode.

The present invention automates the shear to chop out the splice and taper portion of the trailer while preserving synchronization of the cut-off knives with the registration marks of the trailer in a manner that minimizes scrap and reduces the possibility of an exceptionally long scrap sheet which obstructs the sheet-stacking mechanism.

SUMMARY OF THE INVENTION

The present invention is directed to method and apparatus of automatically controlling a cut-to-mark cut-off machine which cuts a preprinted web divisible into a leader provided with a first set of registration marks and a trailer provided with a second set of registration marks wherein the registration marks are separated by a transition such as a splice.

A target capable of being sensed is applied to the trailer adjacent the initial registration mark of the second set upstream of the transition. The leader is cut by the cut-off machine knives in synchronization with the registration marks of the first set downstream of the transition. The target is sensed when it appears at a station upstream of the cut-off machine.

The target is tracked to a shear upstream of the cut-off machine, and the shear is operated automatically to repetitively sever the web transversely and chop out the splice and a portion of the trailer. The leading edge of the trailer is then tracked to a second position, between the shear and the cut-off machine, and a logic control tracks the first registration mark following leading edge from that position to the cut-off machine. When the mark appears at the cut-off machine, the cut-off knives are operated to "crop" cut the trailer at the mark. Thereafter, the cut-off knives cut the trailer in synchronization with the following trailer registration marks, i.e., in the cut-to-mark mode.

An object of the invention is to automatically chop out the splice and any objectionable portion of the trailer while preserving synchronization between the cut-off knives and registration marks in a manner which is simple, inexpensive and reliable.

Another object of the invention is to automate a cut-to-mark cut-off machine to effect an automatic order change while operating the machine in the cut-to-mark mode.

Other objects and advantages will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawing a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a block diagram of the invention described in co-pending application Serial No.

FIGS. 2A and 2B are diagrammatic views of a moving web having spliced portions which is severed by a shear and cut into blanks by the cut-off machine in conventional manner in the cut-to-length mode.

FIGS. 3A and 3B are diagrammatic views of a moving web having spliced pre-printed portions bearing registration marks which is severed by the shear and cut into blanks by the cut-off machine in conventional manner in the cut-to-mark mode.

FIGS. 4A and 4B are diagrammatic views of a moving web having spliced pre-printed portions which is severed by the shear automatically and cut into blanks by the cut-off machine in the cut-to-mark mode without loss of synchronization in accordance with the invention described in co-pending application Ser. No. 265,509

FIG. 5 is a diagrammatic view of a moving web comprising spliced pre-printed portions to be cut into blanks in accordance with the invention described in co-pending application Ser. No. 265,509 for a roll-to-roll change within an order.

FIG. 6 is a block diagram of the invention described in co-pending application Ser. No. 265,509 in use with two cut-off machines of a no-gap order change system.

FIG. 7 is a block diagram of the present invention.

FIG. 8 is a diagrammatic view of a moving web having spliced pre-printed portions bearing registration marks which is severed repetitively by a shear to chop out the splice and an edge taper of the trailer in accordance with the present invention.

FIG. 9 is a block diagram of the present invention in use with two cut-off machines of a no-gap order change system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings in detail, wherein like numerals indicate like elements, there is shown in FIG. 1 a portion of a corrugator which processes a moving web of corrugated paperboard 10.

CONVENTIONAL ELEMENTS OF THE CORRUGATOR

The corrugator includes a glue machine 12 upstream of a double facer machine 14. Downstream of the double facer machine 14, there is provided a rotary shear 16 for severing the web into a leader and trailer, a slitterscorer 18 for slitting and scoring the web in known manner, and a cut-off machine 20. The cut-off machine has rotary knives controlled by a standard logic control 22 connected to an input keyboard 24. The cut-off machine and logic control 22 cut the web into blanks of desired lengths based on the keyboard inputs. The cut-off machine 20 is the type known in the industry as a type B cut-off machine, such as the Reliance machine which has (1) cut-to-length capability with automated order change, and (2) cut-to-mark capability with manual-initiated order change only and with loss of synchronization across a transition in the web such as a gap or a splice.

The present invention is directed to a technique of operating the shear 16 and actuating the logic control 22 to automatically chop out the splice and any objectionable portion of the trailer and fully automate the cut-off machine 20 in the cut-to-mark mode.

Prior Art Order Change: Cut-To-Length And Cut-To-Mark Operation Of Type B Machine

For the reader's convenience, the following summary of operation of cut-off machine 20 is provided in connection with automated order change cut-to-length operation and manual-initiated order change cut-to-mark operation. Details of operation of the machine are well-known in the industry.

Cut-To-Length Order Change

A. "Crop" Cutting The Trailer

For cut-to-length order change, the control 22 automatically fires the shear 16, by a technique described hereafter, causing the shear to sever the web so as to divide the web into a leader 62 and trailer 64. See FIGS. 2A and 2B. Old order blanks are cut from the leader, and new order blanks are cut from the trailer. The electrical connection between control 22 and shear 16 is not shown in FIG. 1 for purposes of simplicity and since the connection is not used in practicing the present invention.

A measuring wheel 96 and encoder 98 located between the shear 16 and photoelectric cell 44 provide a pulse stream indicative of trailer displacement. An encoder 100 connected to the cut-off machine pull rolls 102 provides a pulse stream indicative of leader displacement. The photoelectric cell 44 is connected directly to the control 22. The cell detects the trailing edge of the leader 62 and triggers the control 22 to cause the control to track the trailing edge of the leader to the cut-off machine by initiating a count of the pull roll encoder pulses. When the count reaches the known distance A between the cell 44 and cut-off machine 20, indicating that the trailing edge of the leader has reached the cut-off machine, control 22 "cocks" the cut-off knives. The knives remain "cocked" in anticipation of receiving the trailer 64.

The photocell also detects the leading edge of the trailer 64 and triggers the control 22 to track the leading edge of the trailer to the cut-off machine by initiating a count of the measuring wheel encoder pulses. When the count of measuring wheel encoder pulses reaches the known distance A between the cell 44 and cut-off machine 20, the control 22 operates the cut-off knives to "crop" cut the leading edge of the trailer 64. The "crop" cut is the first cut of the trailer 64, and it is made to clean up the relatively imprecise, ragged leading edge of the trailer resulting from the shear cut. See FIG. 2B.

When the "crop" cut is made, the control 22 initiates another count of measuring wheel encoder pulses. When that count reaches the desired blank length L' for the new order, as input at the keyboard 24, the control 22 operates the cut-off knives to again cut the web. This produces the first new order blank of length L'. This operation of the cut-off knives by control 22 is repeated throughout the new order and is termed "cut-to-length".

B. Firing The Shear

As indicated above, the shear 16 is automatically fired by control 22 to sever the web during an order change. Actually, the shear 16 is operated to sever the web at the end of the last blank in the old order, i.e. at the end of the last blank in what is to become the leader 62. See FIG. 2A. At start-up, prior to any order change, the leading edge of the leader 62 moves towards the cut-off machine 20 and traverses the cell 44. At this time, control 22 computes the position of the end of the last blank relative to the cut-off machine 20 based on the desired blank length L for blanks cut from the leader or old order, the number n of blanks to be cut in the order, and the known separation A between the cell 44 and the cut-off machine 20. Specifically, the position P of the end of the last blank upstream of the cut-off machine 20 when the leading edge of leader 62 traverses the cell 44 is:

P=A+L.times.n

When the leading edge of the leader 62 traverses cell 44, the cell triggers control 22. The control initiates a count of the measuring wheel encoder pulses to track the end of the last blank in the order from the position P to the shear 16. When the count reaches the known separation S between the shear 16 and cut-off machine 20, the control 22 fires the shear, and the shear severs the web at the end of the last blank in the order.

Thereafter, a gap is created between the leader and trailer, for example by speeding up the leader in conventional manner. See FIG. 2B. As the gap traverses the cut-off machine 20, the cut-off machine is said to be "in the gap" and the machine remains in the cut-to-length mode with the cut-off knives "cocked". The cut-off machine 20 "crop" cuts the trailer 64 as previously described and continues to operate in the cut-to-length mode based on the new desired blank length L'.

From the foregoing, it can be appreciated that there are two aspects of operation of the cut-off machine 20 during an order change in the cut-to-length mode: (1) firing the shear to sever the web at the end of the last blank in the old order, and (2) operating the cut-off knives to "crop" cut the trailer and then continue to cut the trailer in the cut-to-length mode after the shear has been fired to sever the web.

CUT-TO-MARK ORDER CHANGE

A. Manual-Initiated Shear

For cut-to-mark operation, the web 10 is provided with printed indicia and registration marks to enable blanks of the desired length to be cut from the web such that each blank bears the same printed indicia. For the B type cut-off machine 20, the control 22 cannot fire the shear to effect an automated order change in the cut-to-mark mode, and synchronization between the cut-off knives and web registration marks cannot be maintained from the leader 62 to the trailer 64. Thus, the shear must be fired in response to a manually initiated command, and an upstream or downstream adjust is required to synchronize the cut-off knives to the trailer registration marks.

B. Optical Sensor "Windows"

An optical sensor 66, located at least one cut-off knife circumference from cut-off machine 20, is periodically enabled by control 22 to scan a finite portion of the web for registration marks over a time "window". The dimensions of the "window" may vary. Typically, the "window" extends a minimum of two inches upstream and two inches downstream of a registration mark. The registration marks typically have a width of 0.25 inch along the web edge and the length of 6 inches transverse of the web. The location of the registration marks is preferably along an edge of the web 10, but the marks may be located in the central portion of the web if desired.

While the leader 62 passes through the cut-off machine 20, the cut-off knives are operated by control 22 to cut the leader at the leader registration marks in the cut-to-mark mode. When the trailing edge of the leader is tracked to the cut-off machine 20, the control 22 "cocks" the cut-off knives. Before the trailer 64 reaches the optical sensor, while the cut-off machine 20 is "in the gap", the cut-off knives remain "cocked". When the leading edge of the trailer eventually reaches cell 44, the cell 44 triggers the control 22 as previously described. The control 22 then tracks the leading edge of the trailer from the cell to the cut-off machine 20 which "crop" cuts the leading edge of the trailer in the cut-to-length mode. See FIG. 2B.

C. Upstream Or Downstream Adjust

To bring the cut-off machine 20 into cut-to-mark operation following the "crop" cut, whereby the cut-off knives cut the trailer in response to detection of registration marks in the optical sensor "windows", it is necessary for the operator to manually depress an upstream or downstream adjust button. During an upstream or downstream adjust operation, the optical sensor "window" is advanced or delayed by the control 22 until it first coincides with a registration mark. That is, the optical sensor "window" is displaced in time until it coincides with the passage of a registration mark across the optical sensor. In the cut-to-length mode, the optical sensor "windows" are generated by control 22, based on the count of measuring wheel encoder pulses and the keyboard entry of blank length L', just prior to each cut of the cut-off knives. At the first coincidence of a registration mark and "window", the control 22 initiates a count of the measuring wheel encoder pulses. The next "window" is generated while the cut-off knives are still operating in the cut-to-length mode, and if that "window" coincides with the next registration mark the control 22 computes the separation between the two "windows" in terms of measuring wheel encoder pulses and uses that number to periodically enable the optical sensor thereafter. The cut-off knives are then operated by control 22 to cut the web in response to detection of each registration mark in a "window", and the cut-off machine is said to operate in the "cut-to-mark" mode.

From the foregoing, it can be appreciated that there are three deficiencies in operation of the cut-off machine 20 during an order change in the cut-to-mark mode: (1) the shear 16 must be fired manually to sever the web, (2) the cut-off knives initially "crop" cut the leading edge of the trailer but are not in synchronization with the trailer registration marks, and (3) a manually initiated adjust is necessary to bring the cut-off machine into cut-to-mark operation on the trailer.

The Invention Described In Co-Pending Application Ser. No. 265,509

The invention described in co-pending application Ser. No. 265,509 is directed to an automated control wherein the cut-off machine 20 is operated without loss of synchronization in the cut-to-mark mode despite a transition in registration marks on the web such as would occur across a splice, including: (1) synchronizing the cut-off machine and shear for automated shear operation, and (2) "crop" cutting the trailer at the first registration mark and eliminating the manual-initiated upstream or downstream adjust.

A. Automated Order Change

In the preferred embodiment of the invention described in co-pending application Ser. No. 265,509, a target 26 is applied to the web 10 in alignment with the initial registration mark of the second set following the transition between first and second sets of marks on the web. See FIG. 4A. The transition occurs at a splice between webs 62 and 64 effected by adhesive tape or the like. The target 26 is preferably a magnetically detectable tape such as a metallic tape but it may have other forms. The target 26 is sensed by a magnetic sensor 28 which causes a pulse generator 30 to enable a pair of counters 32 and 34. A measuring wheel 36 is driven by the web 10 and is connected to an encoder 38. The measuring wheel and encoder are well-known devices which provide a pulse stream indicative of web travel. The pulses generated by the encoder 38 are counted by counters 32 and 34 to track the target as described hereafter.

Magnetic sensor 28 and measuring wheel 36 are located at stations upstream of and at predetermined web distances from the cut-off machine 20 and shear 16. Counter 32 is preset to the web distance between the magnetic sensor 28 and shear 16. The counter tracks the target 26 to the shear 16 by counting the measuring wheel encoder pulses. When counter 32 counts out, the predicted position of the target 26 is at the shear. A shear fire control signal is generated by counter 32 at this time to cause a shear fire control 40 to automatically activate the shear knives. The shear knives sever the web 10 immediately downstream of the splice. See FIG. 4A. The cut made by the shear 16 is imprecise and ragged but it does separate the web 10 into a leader 62 and trailer 64. The trailer has the target 26 thereon. A gap is formed between the leader and trailer in a known manner to permit adjustment of the slitter-scorer 18 and cut-off machine 20 for the new order before the trailer 64 reaches either device. See FIG. 4B.

Initially, control 22 causes the cut-off knives to cut the leader 62 in the cut-to-mark mode. When the cut-off machine 20 is "in the gap", however, the cut-off knives are "cocked". As previously explained, this is a conventional feature of the control 22.

Counter 34 is preset to the web distance between the magnetic sensor 28 and the cell 44. The counter 34 tracks the target 26 to the cell 44 by counting the measuring wheel encoder pulses. When counter 34 counts out, the predicted position of target 26 is at the cell 44 and a tracking signal is transmitted by the counter through a logic gate 42 to the control 22. The cell 44, which is conventionally used to trigger the control 22 in the cut-to-length mode is blocked by the gate 42.

Gate 42 may be any suitable electronic logic gate conditioned by a manually operable two state select switch 74. In one state, corresponding to conventional cut-to-length operation, switch 74 enables gate 42 to pass the output of cell 44 while blocking the output of counter 34. In the other state, corresponding to cut-to-mark operation according to the present invention, switch 74 enables gate 42 to pass the output of counter 34 while blocking the output of cell 44.

In the cut-to-mark mode as selected by switch 74, the tracking signal from counter 34 is passed by gate 42 to trigger control 22 which now tracks the target 26, rather than the leading edge of the trailer, from the position of cell 44 to the cut-off machine 20. The control 22 then causes the cut-off knives to "crop" cut the trailer at the target 26, adjacent the first registration mark on the trailer. See FIG. 4B. Thus, the knives do not "crop" cut the leading edge of the trailer but, instead, "crop" cut the trailer at the first registration mark itself. Since the target 26 is applied adjacent the first registration mark, the mark will appear in the optical sensor "window" immediately prior to the "crop" cut. Thereafter, the cut-off knives will operate in synchronization with all remaining registration marks on the trailer, that is, the knives will cut the trailer in the cut-to-mark mode under control of logic control 22.

From the foregoing, it can be appreciated that the existing logic control 22 associated with cut-off machine 20 is designed to track the leading edge of the trailer between cell 44 and the cut-off machine 20 based on a count of measuring wheel encoder pulses; and it is designed to cause the cut-off knives to "crop" cut the leading edge of the trailer. Tracking of the leading edge of the trailer by control 22 commences in response to a signal from cell 44 which is generated when the cell detects the leading edge of the trailer downstream of the shear. The existing control 22 provides automated operation during an order change in the cut-to-length mode only. Automated order change in the cut-to-mark mode is not possible without the present invention.

The invention described in co-pending application Ser. No. 265,509 substitutes the target 26 for the leading edge of the trailer, and it substitutes the tracking signal from counter 34 for the signal generated by cell 44. The logic control 22 therefore tracks the target 26 instead of the leading edge of the trailer. As a result, the cut-off knives automatically begin to cut the trailer at the target, i.e. at the first registration mark on the trailer. Since the mark will be within the optical sensor "window", the cut-off machine 20 automatically operates in the cut-to-mark mode in synchronization with all following registration marks on the trailer.

The invention described in co-pending application Ser. No. 265,509 utilizes commercially available components which are few in number and which are arranged so as to implement the existing logic control 22 but in a manner to effect cut-to-mark operation without losing synchronization due to a transition between first and second sets of registration marks.

The invention described in co-pending application Ser. No. 265,509 is broadly directed to preserving cut-to-mark operation of the cut-off knives despite a transition between the first and second sets of registration marks. The invention encompasses synchronization between the optical sensor "windows" and two sets of like registration marks across a transition such as a splice, wherein there is a single order and no order change. The splice is made necessary by a roll-to-roll change within the order.

B. Roll-To-Roll Change Within An Order

The web 10 may be pre-printed, bearing like registration marks separated by a splice as shown in FIG. 5. In FIG. 5, the old roll web or leader is designated 62 and the new roll web or trailer is designated 64. The target 26 is applied to the new roll web 64 adjacent the first registration mark on the web.

For operation during a roll-to-roll change within an order, synchronization between the optical sensor "windows" and registration marks would be lost as the splice (transition) traverses the optical sensor. That is, as the splice passes the optical sensor, the first registration mark on the trailer 64 does not coincide with an optical sensor "window" due to the non-uniform spacing between the last registration mark of the leader 62 and the first registration mark of the trailer 64. Accordingly, the control 22 reverts automatically to the cut-to-length mode wherein the knives cut the trailer based on the keyboard entry of desired blank length L and wherein the control 22 periodically enables the optical sensor for a time "window" each time that the count of measuring wheel encoder pulses reaches the length L. The operator must initiate an upstream or downstream adjust to bring the optical sensor "windows" back into synchronization with the registration marks on the new roll web 64. Many waste sheets having truncated pre-printed material can be cut before synchronization is re-established.

Operation in the cut-to-mark mode during a roll-to-roll change within an order is identical to that already described in connection with the automated order change. Thus, the shear 16 is automatically fired by counter 32 to sever the web 10 immediately downstream of the splice into the leader and trailer. The leader is cut into blanks by the cut-off knives which are operating in the cut-to-mark mode. A gap is created between the leader and trailer to afford the cut-off machine 20 sufficient time to "cock" the cut-off knives before the trailer, and in particular the target 26, reaches the cut-off machine. When the cut-off machine is "in the gap", the knives are "cocked". Thereafter, the trailer is "crop" cut at the target, i.e., at the first registration mark, and the cut-off knives cut the trailer in the cut-to-mark mode in synchronization with all following registration marks.

The invention described in co-pending application Ser. No. 265,509 also has application in a no-gap type order change system.

C. No-Gap Type Order Change

In a no-gap order change system, as in a gap type system, the web must be severed to separate the old and new orders. In a no-gap system, however, the web 10 moves at high speed before and after traversing the shear 16; and instead of creating a gap by accelerating the leader and then feeding the leader and trailer to the same cut-off machine, the leader is cut by one cut-off machine 20 while the trailer is directed automatically to a second identical cut-off machine 20' as shown in FIG. 6. Both machines 20 and 20' are B type machines as previously described. Before the trailer reaches the second cut-off machine 20', the machine generates sensor "windows" as in the cut-to-length mode, i.e., based on the input of new order blank length from keyboard 24 which may actually comprise two keyboards, one for each cut-off machine.

The counters 32 and 34 operate as in the gap type order change, to track the target 26 from sensor 28 to shear 16 and cell 44. When the target is tracked to shear 16, the shear knives are fired automatically by shear control 40 to sever the web 10 into the leader 62 and trailer 64. The trailer is diverted in conventional manner by a diverter mechanism 90 to the second cut-off machine 20'.

When the target is tracked to cell 44, the gate 42 toggles a gate 92, which is a bi-stable device having complementary outputs A and B, in response to the tracking signal output of counter 34. The control 22 tracks the trailing edge of the leader 62 to machine 20, and it causes the machine 20 cut-off knives to cut the last blank from the leader and then "cock" in preparation for a "crop" cut of the trailer 64. The trailer, however, is diverted to the cut-off machine 20'. The machine 20 cut-off knives therefore remain "cocked" until the output A of gate 92 assumes a complementary value when the gate is again toggled at the next order change.

While the control 22 maintains the machine 20 knives in the "cocked" position in response to output A of gate 92, the control 22' tracks the target 26 from cell 44 to cut-off machine 20' in response to the complementary output B of gate 92. When the target 26 reaches cut-off machine 20', the cut-off knives are operated to "crop" cut the trailer 64 at the target, i.e., at the first registration mark on the trailer. Thereafter, the cut-off knives are operated by control 22' in the cut-to-mark mode to cut the trailer into blanks at all following registration marks.

At the next order change or operation of shear 16, the next target is tracked to cell 44 in the manner already described, and the counter 34 output is passed by gate 42 to toggle gate 92, reversing the complementary outputs A and B. The control 22' "cocks" the machine 20' cut-off knives, and the control 22 tracks the target to machine 20 and operates the machine 20 cut-off knives to "crop" cut the new trailer at the target. Transfer of operation between the two cut-off machines 20 and 20' occurs in the manner described at each subsequent order change or operation of shear 16.

It should be noted that the invention described in co-pending application Ser. No. 265,509 is directed to cut-to-mark operation of a cut-off machine 20 or cut-off machines 20 and 20' during order changes or roll-to-roll changes. Although the cell 44 is used by the standard control 22 (or 22') in standard cut-to-length and cut-to-mark operation, the cell is never used in cut-to-mark operation according to the present invention. Thus, gate 42 is always conditioned by select switch 74 to block the cell 44 output and pass instead the output of counter 34 when practicing the method of the invention.

The Present Invention:

Chopping Out The Splice

The automated cut-to-mark control described above provides a convenient retrofit of the existing B type cut-off machine 20 and associated logic control 22 and has application in (1) an automated order change, and (2) a roll-to-roll change within an order. In both applications, the leader 62 and trailer 64 are separated by a splice.

Typically, the trailer 64 has a tapered edge at the area of the splice where there is a change in width between the webs. The edge taper is mechanically cut by the operator in preparation for the splice. The edge taper may also be accompanied by a poor taper in the glue applied to the web 64 due to problems inherent in adjusting the glue dams in the single facer machine for an order change. It is therefore desirable to chop-out the splice and the portion of trailer 64 having the edge and glue taper. It is understood hereafter that by "chopping out the splice" is meant chopping the splice as well as any following web portion as desired.

An automated cut-to-mark control with a splice chop-out feature in accordance with the present invention is shown in FIG. 7. The control has application in both (1) gap and no-gap order changes, and (2) roll-to-roll change.

A. Gap Type Order Change

The target 26 is applied adjacent the first registration mark on the trailer 64. See FIG. 8. The target 26 is tracked from the sensor 28 to a point just upstream of the shear 16 as previously described. Thus, the counter 32 initiates a count of the measuring wheel encoder 38 pulses when the target 26 is detected at sensor 28. When the target reaches the shear, the counter 32 emits a signal which is passed by a logic gate 70 to the shear fire control 40. The shear control then fires the shear knives, causing the knives to sever the web 10 transversely into the leader 62 and trailer 64. The first transverse shear cut is designated S1 in FIG. 8 and is located just downstream of the splice.

The logic gate 70 is conditioned by a select switch 72 which is a manually operable two state switch. In one state, the switch is operated to condition gate 70 to activate the fire control 40 for one shear cut in response to the counter 32 output for a cut-to-mark order change or roll-to-roll change without splice chop-out, already described. In the other state, the select switch 72 conditions the gate 70 to keep the fire control 40 activated for several shear cuts in response to the counter 32 and the output of a counter 82 for a cut-to-mark order change or roll-to-roll change with splice chop-out, described hereafter.

During a gap type order change, the leader 62 is accelerated to create the gap between the leader and trailer 64. To chop out the splice, the shear knives are repetitively operated to effect a preselected number of cuts, for example S1, S2 and S3 as shown in FIG. 8. Repetitive operation of the shear knives is supervised by a detector 80, counter 82 and the gate 70. See FIG. 7. The detector 80 generates a pulse signal for each revolution of the shear knives and may be a magnetic pickup or the like provided with a pulse generator. Pulses emitted by the detector are counted by counter 82 which is preset to a number representing the number of shear cuts (S1-S3) desired. The number of shear cuts desired is the number of sheets to be chopped out plus one. This number is based on the known circumference of the shear knives, the known web speed, and the known length of the material to be chopped out. The number is preset by means of operator accessible thumbwheel switches 102. Gate 70 maintains the fire control 40 active in response to the counter 32 output until the preset number is counted out by counter 82. The counter then disables the gate 70 thereby de-activating the fire control 40. As a result, the shear knives are prevented from further cutting the web. While the shear knives cut the web, the scrap sheets chopped from the web are collected in a hopper 84.

As the gap approaches the cut-off machine 20, the cut-off knives cut the leader 62 in the cut-to-mark mode as previously described. When the cut-off machine is "in the gap", the cut-off knives remain "cocked". In the automated cut-to-mark order change without splice chop-out, the counter 34 tracks the target 26 from shear 16 to the cell 44 between the shear and cut-off machine 20, and the counter 34 output is passed by gate 42' to logic control 22. Where splice chop-out is desired, however, the gate 42' is conditioned to block the output of counter 34 by a select switch 74'. Select switch 74' is a three state switch. In one state, the switch conditions gate 42' to pass the output of cell 44 to the control 22, corresponding to standard cut-to-length operation during an order change as previously described. In the second state, the switch conditions gate 42' to block the output of cell 44 and pass the output of counter 34 to the control 22, corresponding to cut-to-mark operation during an order change without splice chop-out as already described. In the third state, the select switch conditions gate 42' to block the outputs of cell 44 and counter 34 while enabling gate 42' to pass the output of a logic gate 86 to the control 22, corresponding to cut-to-mark operation during an order change with splicee chop-out as in the present invention.

Although select switch 74' conditions gate 42' to block the output of counter 34 during a cut-to-mark order change with splice chop-out, the output of the counter enables a counter 88 to initiate a count of measuring wheel encoder 38 pulses. Thus, the counter 88 initiates a count of the measuring wheel encoder pulses when the target 26 would appear at the location of cell 44 if it were not chopped out by shear 16. Counter 88 is a modulo type counter which repetitively counts up to a preselected number corresponding to the desired length of sheets L' to be cut from the trailer 64. The presected number is preset by means of operator accesible thumbwheel switches 100 and changes from order to order. The counter emits a pulse each time that the count of measuring wheel encoder pulses reaches the preselected number or sheet length L'. The pulses emitted by counter 88 are referred to as "phantom" pulses, and these pulses represent the registration marks on the trailer downstream of the cell 44. One of the "phantom" pulses is fed through logic gate 86 to gate 42' in response to an enable signal generated by a counter 90 as described hereafter.

The counter 90 does not enable gate 86 to pass the "phantom"pulse until the shear 16 has chopped out the desired amount of scrap material. The counter 90 is preset to a number which represents the known distance between the shear 16 and the cell 44. The counter is enabled to count by the counter 82 when the counter 82 counts the last revolution of the shear knives corresponding to the last shear cut S3.

When the counter 90 is enabled to count, it counts the measuring wheel encoder pulses to the preset number. When the count maintained by the counter reaches the preset number, this indicates that the last shear cut (S3) is at the cell 44, and the counter then enables gate 86.

The presence of the first registration mark following the last shear cut (S3) at the position of cell 44 is represented by the first "phantom" pulse generated by counter 88 after counter 90 enables gate 86. This pulse is passed by gate 86 to gate 42'. Gate 42' is conditioned, as previously explained, to pass the output of gate 86 to control 22 when splice chop-out is selected by switch 74'. The "phantom" pulse generated by counter 88 therefore triggers the control 22 which then tracks the registration mark from the cell 44 to cut-off machine 20 to effect a "crop" cut of the trailer at the registration mark. See FIG. 8. The control 22 then operates the cut-off knives in the cut-to-mark mode in synchronization with the following registration marks on the trailer 64 as previously described.

B. Roll-To-Roll Change Within An Order

To chop-out the splice across a roll-to-roll change in the cut-to-mark mode, the invention is operated in the same manner as in effecting a splice chop-out during an order change described above. The target 26 is tracked to the shear 16 by counter 32. Select switch 72 is manually operated to condition gate 70 to operate the shear fire control 40 to cause the shear knives to repetitively cut the web. The shear control 40 remains enabled by gate 70 while the shear knives rotate a preselected number of revolutions corresponding to the desired number of shear cuts S1-S3. During this time, counter 34 tracks the target 26 to cell 44 as if the target 26 had not been removed from the web line. The output of counter 34 therefore indicates the imaginary position of the target 26 at cell 44 had the target not been chopped out of the web.

The output of counter 34, corresponding to the imaginary position of the target at cell 44, enables counter 88 to generate the "phantom" pulses representative of the successive registration marks which follow the target on trailer 64 as already explained. When the desired amount of web material has been chopped out by the shear knives, counter 82 enables counter 90 to track the last shear cut S3--which is now the leading edge of the trailer--from shear 16 to cell 44. When the counter 90 indicates that the last shear cut S3 is at cell 44, counter 90 enables logic gate 86. The first "phantom" pulse from counter 88 which is passed by gate 86 represents the first registration mark following the shear cut S3 at the position of the cell 44. This "phantom" pulse is passed by gate 42' to trigger the control 22. The control then tracks the registration mark to the cut-off machine 20 to effect a "crop" cut at the registration mark. The cut-off machine 20 thereafter cuts the trailer 64 in the cut-to-mark mode synchronized to all following registration marks.

C. No-Gap Type Order Change

Operation of the invention for a no-gap order change is essentially the same as for the gap type order change previously described.

Referring to FIG. 9, the splice and taper are chopped out by repetitively operating the shear knives under control of gate 70 and counters 32 and 82. The first registration mark following the last shear cut is tracked electronically to the cell 44 by counters 34, 88 and 90. The first "phantom" pulse generated by counter 88 after gate 86 is enabled by counter 90 (indicating that the last shear cut is at cell 44) toggles the gate 92. That "phantom" pulse represents the first registration mark which follows the last shear cut. The appropriate control 22 or 22'--as selected by the complementary output A or B of gate 92--then tracks that registration mark to the cut-off knives which "crop" cut the trailer at the registration mark. The trailer is then cut at all following registration marks by the cut-off knives in the cut-to-mark mode.

The transfer between cut-off machine 20 and 20' occurs as previously described for each no-gap type order change.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

1. A method of automatically controlling a cut-off machine having knives operable in a cut-to-mark mode wherein the knives cut a moving web divisible into a leader having a first set of registration marks and a trailer having a second set of registration marks, there being a transition between the first and second sets of marks, comprising:

(a) applying a target to the trailer adjacent a first preselected registration mark of the second set;

(b) tracking the target electronically to a shear upstream of the cut-off machine;

(c) automatically and repetitively severing the web transversely at the shear two or more times when the target is tracked to the shear whereby a preselected portion of the web comprising the transition between said registration marks is chopped out of the web;

(d) tracking the leading edge of the trailer electronically from said shear to a position intermediate the shear and said cut-off machine after said preselected web portion has been chopped from the web;

(e) causing the knives to cut the trailer automatically at a second preselected registration mark of the second set following the leading edge of the trailer; and

(f) causing the knives to cut the trailer automatically in the cut-to-mark mode at the registration marks of the second set which follow said second preselected registration mark.

2. The method in accordance with claim 1 wherein the second preselected registration mark is the first mark of the second set following the leading edge of the trailer.

3. The method in accordance with claim 1 wherein said target is a magnetically detectable target.

4. A method of automatically controlling at least first and second cut-off machines each having knives operable in a cut-to-mark mode wherein the knives cut a moving web divisible into a leader having a first set of registration marks and trailer having a second second of registration marks, there being a transition between the first and second sets of marks, comprising:

(a) directing the leader to said first cut-off machine;

(b) causing the knives of said first cut-off machine to cut the leader in the cut-to-mark mode at the registration marks of the first set;

(c) applying a target to the trailer adjacent a first preselected registration mark of the second set;

(d) tracking the target electronically to a shear upstream of the cut-off machines;

(e) automatically and repetitively severing the web transversely at the shear two or more times when the target is tracked to the shear whereby a preselected portion of the web comprising the transition between said registration marks is chopped out of the web;

(f) tracking the leading edge of the trailer electronically from said shear to a position intermediate the shear and said cut-off machines after said preselected web portion has been chopped from the web;

(g) directing the trailer to said second cut-off machine;

(h) causing the knives of said second cut-off machine to cut the trailer automatically at a second preselected registration mark of the second set following the leading edge of the trailer; and

(i) causing the knives of said second cut-off machine to cut the trailer automatically in the cut-to-mark mode at the registration marks of the second set which follow said second preselected registration mark.

5. The method in accordance with claim 4 wherein said target is a magnetically detectable target.

6. The method in accordance with claim 4 wherein the second preselected registration mark is the first mark of the second set following the leading edge of the trailer.

7. Apparatus for automatically controlling a cut-off machine having knives operable in a cut-to-mark mode wherein the knives cut a moving web divisible into a leader having a first set of registration marks and trailer having a second set of registration marks, there being a transition between the first and second sets of marks, said trailer being provided with a target adjacent a first preselected registration mark of the second set, comprising:

(a) a shear upstream of said cut-off machine for severing the web transversely;

(b) means for tracking said target electronically to said shear and for causing said shear to sever the web repetitively two or more times when said target is tracked to said shear whereby a preselected portion of the web comprising the transition between said registration marks is chopped out of the web;

(c) means for tracking the leading edge of the trailer electronically from said shear to a position intermediate the shear and said cut-off machine after said preselected web portion has been chopped from the web; and

(d) means for causing said knives to repetitively cut the trailer at said second set of registration marks in the cut-to-mark mode beginning at the position of a second preselected registration mark following the leading edge of the trailer.

8. Apparatus in accordance with claim 7 wherein said target is a magnetically detectable target and said means for tracking the target to the shear includes a magnetic sensor.

9. Apparatus in accordance with claim 7 including means for causing said knives to cut the leader in the cut-to-mark mode at said first set of registration marks, and means for creating a gap between the leader and trailer as the leading edge of said trailer is tracked from said shear to said position intermediate the shear and said cut-off machine.

10. Apparatus for automatically controlling at least first and second cut-off machines each having knives operable in a cut-to-mark mode wherein the knives cut a moving web divisible into a leader having a first set of registration marks and a trailer having a second set of registration marks, there being a transition between the first and second sets of marks, said trailer being provided with a target adjacent a first preselected registration mark of the second set, comprising:

(a) a shear upstream of said cut-off machine for severing the web transversely;

(b) means for tracking said target electronically to said shear and for causing said shear to automatically sever the web repetitively two or more times when said target is tracked to said shear whereby a preselected portion of the web comprising the transition between said registration marks is chopped out of the web;

(c) means for directing the leader to said first cut-off machine;

(d) means for causing the knives of said first cut-off machine to cut the leader in the cut-to-mark mode at the registration marks of the first set;

(e) means for tracking the leading edge of the trailer from said shear to a position intermediate the shear and said cutoff machines after said preselected web portion has been chopped from the web;

(f) means for directing the trailer to said second cut-off machine; and

(g) means for causing the knives of said second cut-off machine to repetitively cut the trailer at said second set of registration marks in the cut-to-mark mode beginning at the position of a second preselected registration mark following the leading edge of the trailer.

11. Apparatus according to claim 10 including means for alternately cocking the knives of one of said first and second cut-off machines while causing the knives of the other of said cut-off machines to cut the trailer.