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Publication numberUSRE30628 E
Publication typeGrant
Application numberUS 06/032,886
Publication dateMay 26, 1981
Filing dateApr 24, 1979
Priority dateJun 7, 1974
Publication number032886, 06032886, US RE30628 E, US RE30628E, US-E-RE30628, USRE30628 E, USRE30628E
InventorsMasateru Tokuno, Masayuki Matsuura, Noboru Shinmura, Masayoshi Kaneko
Original AssigneeRengo Kabushiki Kaisha (Rengo Co., Ltd.), Nippon Riraiansu Kabushiki Kaisha
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Web cutting control system
US RE30628 E
Abstract
A web cutting control system controlling the speed of a rotary cutter for automatic, continuous and precise cutting of a web fed at a constant speed into predetermined lengths or on the marks on the web. Two transducers generate pulses the number of which corresponds to the web feed length and the rotating angle of the rotary cutter, respectively. Three sensors detect the marks on the web, the completion of cutting, and the arrival of the cutter blades, respectively, to control the flow of signals. A desired cutting length or the distance between the mark detection point and the point of completion of cutting is preset. A reversible counter receives the pulses from these two transducers and the difference signal between the preset value and a reference signal and performs reversible counting thereof, the result of which is used to control the speed of motor for the rotary cutter to bring its speed into synchronization with the web feed speed for accurate cutting.
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Claims(2)
What is claimed is:
1. A control system for cutting a web fed .[.at a constant-speed.]. by means of a rotary cutter driven by a motor selectively either into predetermined lengths or at fixed positions thereof, said control system comprising in combination:
a. first transducer for generating pulses, the number thereof being proportional to the length of the web which has been fed;
b. a second transducer for generating pulses, the number thereof being proportional to the angle through which said rotary cutter has rotated;
c. a first setting means for setting reference pulses, the number thereof being predetermined by a fixed rotating angle of said rotary cutter;
d. a first sensor for detecting the marks put beforehand on the web to give a mark detection signal,
e. a second sensor for detecting completion of each cutting operation to give a cutting completion detection signal;
f. a third sensor for giving a mark distance discriminating signal for discrimination whether the detection of the next mark occurs before or after the completion of cutting on the last mark;
g. a second setting means for digitally setting selectively either a desired cutting length or the distance between the mark detection point and the cutting completion detection point;
h. a first reversible counting means responsive to a detection signal from said first sensor for counting any difference between the value preset on said first setting means and the value preset on said second setting means;
i. an addition/subtraction discriminating means for comparing the value from said first setting means with the value from said second setting means to couple said difference between said two values to said first reversible counting means as a signal to be added or a signal to be subtracted according to the result of comparison;
j. .[.said first.]. .Iadd.a second .Iaddend.reversible counting means receiving the pulses from said first transducer as a signal to be subtracted and the pulses from said second transducer as a signal to be added as well as the difference between said two values and performing reversible counting thereof;
k. a .[.differentiating.]. .Iadd.differencing .Iaddend.means for obtaining any difference between the result of said reversible counting by said .[.first.]. .Iadd.second .Iaddend.reversible counting means and a voltage proportional to the web feed speed;
l. a motor speed control means for discriminating the polarity of the output voltage from said .[.differentiating.]. .Iadd.differencing .Iaddend.means and controlling the speed of the motor for driving the rotary cutter according to the polarity and quantity of said output voltage; and
m. .[.a second.]. .Iadd.said first .Iaddend.reversible counting means .Iadd.further being .Iaddend.for subtracting from the preset value on said .[.first sensing.]. .Iadd.second setting .Iaddend.means a value corresponding to the length of the web which has been fed from the instant of detection by said first sensor to the instant of detection by said second sensor, in case the mark detection signal from said first sensor arrives .[.inn.]. .Iadd.in .Iaddend.advance of the cutting completion detection signal from said second sensor after the mark distance discriminating signal has come from said third sensor. .Iadd. 2. A control system for controlling the cutting of a web into predetermined lengths by means of a rotary cutter driven by a motor; said control system comprising in combination;
(a) a first transducer means for generating pulses, the number thereof being proportional to the length of the web which has been fed;
(b) a signal generator means for generating a signal proportional to the web speed;
(c) a second transducer means for generating pulses, the number thereof being proportional to the angle through which said rotary cutter has rotated;
(d) means for providing a first reference value, the magnitude thereof being related to the swept circumference of said rotary cutter;
(e) a sensor for establishing a knife position datum signal during each cutting cycle;
(f) a setting means for providing a second value representative of a desired predetermined cutting length;
(g) a combining means for combining said first and second values for obtaining a third value representative of the difference therebetween;
(h) a reversible counting means which receives the third value from said combining means in response to each datum signal and which subtracts therefrom the pulses from said first transducer means and adds thereto the pulses from said second transducer means to achieve a resultant count and producing a signal proportional to the resultant count;
(i) a differencing means for obtaining a signal proportional to any difference between said signal proportional to said resultant count and said signal proportional to the web speed; and
(j) motor control means responsive to the signal from said differencing means for controlling the operation of the motor to cut the web into said predetermined lengths. .Iaddend..Iadd. 3. A control system as claimed in claim 2 which is also capable of controlling the rotary cutter for cutting the web at points according to preapplied marks on the web, further comprising:
(a) a further sensor for detecting marks on the web at which the web is to be cut and for giving a mark detection signal;
said setting means having means for providing the second value which, when the system is operating to cut the web at points according to preapplied marks on the web, provides the second value having a magnitude being determined by the distance between the mark detection point and the knife position datum detection point, said distance being a distance from said mark detection point and measured along the path of web travel and around the swept circumference of the cutter to a position which lies in the range from the cutting point to a point spaced around the swept circumference of the cutter from said cutting point;
said combining means having means which, when the system is operating to cut the web at points according to preapplied marks on the web,
(1) when said further sensor detects a mark according to which a cut is to be made no earlier than the occurrence of the knife position datum signal for the next preceding cut, operates in a long-size mode for combining said first and second values to provide a third value representative of the difference between said first and second values, and
(2) when said further sensor detects a mark according to which a cut is to be made before the occurrence of the knife position datum signal for the next preceding cut, operates in a short-size mode for combining said first value, said second value and a value corresponding to the length of web which has been fed from the instant of detection by said further sensor to the occurrence of the knife position datum signal for obtaining the difference between the first and second values reduced by said value corresponding to the length of fed web to obtain a third value;
said reversible counting means having means which, when the system is operating to cut the web at points according to preapplied marks on the web,
(1) when said combining means operates in said long-size mode, during each cutting cycle receives said third value and which receives pulses from said second transducer means as a signal to be added and which on generation of a mark detection signal by said further sensor receives pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal porportional to said resultant count, and
(2) when said combining means operates in said short-sized mode, on generation of each datum signal by said firstmentioned sensor receives said third value and which also receives pulses from said second transducer means as a signal to be added and pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal proportional to said resultant count. .Iaddend..Iadd. 4. A control system as claimed in claim 3 further comprising more sensing means for determining whether the detection of a mark occurs before or after the occurrence of said knife position datum signal for the next preceding mark and for controlling the operation of said combining means and said reversible counting means in the appropriate one of said long-size mode and said short-size mode. .Iaddend..Iadd. 5. A control system for controlling the cutting of a web at points according to preapplied marks thereon by means of a rotary cutter driven by a motor, comprising:
(a) a first sensor for detecting marks on the web at which the web is to be cut and giving a mark detection signal;
(b) a second sensor for establishing a knife position datum signal during each cutting cycle, the distance between consecutive marks being greater than the distance between said first sensor and said second sensor, the latter distance being a distance from said first sensor and measured along the path of the web and around the swept circumference of the cutter to a position which lies in the range from the cutting point to a point spaced around the swept circumference of the cutter from said cutting point;
(c) a first transducer means for generating pulses, the number thereof being proportional to the length of the web which has been fed;
(d) a signal generator means for generating a signal proportional to the web speed;
(e) a second transducer means for generating pulses, the number thereof being proportional to the angle through which said rotary cutter has rotated;
(f) a first means for providing a first reference value, the magnitude thereof being related to the swept circumference of said rotary cutter;
(g) a second means for providing a second value, the magnitude thereof being determined by the distance between the mark detection point and the knife position datum detection point;
(h) a combining means for combining said first and second values for providing a third value representative of the difference therebetween;
(i) a reversible counting means which, during each cutting cycle, receives said third value and which receives pulses from said second transducer means as a signal to be added and which on generation of a mark detection signal by said first sensor receives pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal proportional to said resultant count;
(j) a differencing means for obtaining a signal proportional to any difference between said signal proportional to said resultant count and said signal proportional to the web speed; and
(k) motor control means responsive to the signal from said differencing means for controlling the operation of said motor to cut the web on said
marks. .Iaddend..Iadd. 6. A control system as claimed in claim 5 in which the distance between consecutive marks can also be less than the distance between said first sensor and said second sensor, and
said combining means, when the first sensor detects a mark according to which a cut is to be made no earlier than the occurrence of the knife position datum signal for the next preceding cut, operating in a long-size mode for combining said first and second values to provide the third value representative of the difference between said first and second values, and further having means which, when the first sensor detects a mark according to which a cut is to be made before the occurrence of the knife position datum signal for the next preceding cut, operates in a short-size mode for combining said first value, said second value and a value corresponding to the length of web which has been fed from the instant of detection by said first sensor to the occurrence of the knife position datum signal for obtaining the difference between the first and second values reduced by said value corresponding to the length of fed web to obtain a third value;
said reversible counting means when said combining means operates in said long-size mode, during each cutting cycle receives said third value and which receives pulses from said second transducer means as a signal to be added and which on generation of a mark detection signal by said first sensor receives pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal proportional to said resultant count, and further having means which, when said combining means operates in said short-size mode, on generation of each datum signal by said second sensor receives said third value and which also receives pulses from said second transducer means as a signal to be added and pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal proportional to said resultant count. .Iaddend..Iadd. 7. A control system as claimed in claim 6 further comprising mode sensing means for determining whether the detection of a mark occurs before or after the occurrence of said knife position datum signal for the next preceding mark and for controlling the operation of said combining means and said reversible counting means in the appropriate one of said long-size mode and said short-size mode. .Iaddend..Iadd. 8. A control system for controlling the cutting of a web at points according to preapplied marks thereon by means of a rotary, cutter driven by a motor, comprising:
(a) a first sensor for detecting marks on the web at which the web is to be cut and giving a mark detection signal;
(b) a second sensor for establishing a knife position datum signal during each cutting cycle, the distance between consecutive marks being smaller than the distance between said first sensor and said second sensor, the latter distance being a distance from said first sensor and measured along the path of the web and around the swept circumference of the cutter to a position which lies in the range from the cutting point to a point spaced around the swept circumference of the cutter from said cutting point;
(c) a first transducer means for generating pulses, the number thereof being proportional to the length of the web which has been fed;
(d) a signal generator means for generating a signal proportional to the web speed;
(e) a second transducer means for generating pulses, the number thereof being proportional to the angle through which said rotary cutter has rotated;
(f) a first means for providing a first reference value, the magnitude thereof being related to the swept circumference of said rotary cutter;
(g) a second means for providing a second value, the magnitude thereof being determined by the distance between the mark detection point and the knife position datum detection point;
(h) a combining means for combining said first value, said second value and a value corresponding to the length of web which has been fed from the instant of detection by said first sensor to the occurrence of the knife position datum signal for obtaining the difference between the first and second values reduced by said value corresponding to the length of fed web to obtain a third value;
(i) a reversible counting means which on generation of each datum signal by said second sensor receives said third value and which also receives pulses from said second transducer means as a signal to be added and pulses from said first transducer means as a signal to be subtracted to achieve a resultant count and producing a signal proportional to said resultant count;
(j) a differencing means for obtaining a signal proportional to any difference between said signal proportional to said resultant count and said signal proportional to the web speed; and
(k) motor control means responsive to the signal from said differencing means for controlling the operation of said motor to cut the web on said marks.
Description

The present invention relates to a control system which provides an automatic, continuous and accurate cutting of a web of continuously conveyed cardboard or the like by means of a rotary cutter into constant lengths or at fixed positions without stopping the flow of web at the instant of cutting, with the speed of the rotary cutting being brought into synchronization with the speed at which the web is being fed.

In the cutting of a web continuously fed at a constant speed into desired lengths, the cutting length is usually adjusted by varying the period or interval at which the web is cut. One important problem here is how to achieve complete synchronization of the cutter speed with the web feed speed, thereby minimizing dimensional error of the cut lengths.

A conventional web cutting machine will be described by way of example in connection with FIG. 1. The main shaft C if driven from main motor A through a reduction gearing having a belt B. The feed roller for the web is driven from the main shaft through a bevel gear D. The rotation of the main shaft C is also transmitted through a Reeves drive variable speed mechanism E to a synchronous fly mechanism F, the output of which is coupled to one roll of a rotary cutter G for sychronous drive with the other roll thereof. The speed of the rotary cutter is controlled by means of a motor H connected to the regulating part of Reeves mechanism E and that of synchronous fly mechanism F.

The conventional system provides some degree of synchronization between the web speed and the cutter speed since the rotation of the main shaft is transmitted both to the web feed roller and to the rotary cutter through these mechanisms. However, because of some slipping in the Reeves mechanism E and the complexity of the mechanisms, there is inevitably some cutting error due to transmission error between the elements. High cutting accuracy can not, therefore, be expected. Because both the Reeves mechanism and the synchronous fly mechanism are mechanical ones, the prior art system is slow to follow any change of the cutting length during operation, which results in substantial loss of material due to inaccurate cutting.

An object of the present invention is to provide a web cutting control system which utilizes modern electronics technology to control the speed of the rotary cutter, thereby bringing it into complete synchronization with the web running speed before the instant of cutting to ensure that the web is cut accurately into predetermined lengths or at fixed positions.

Another object of the present invention is to provide a web cutting control system which provides automatic, accurate and continuous cutting of a continuously conveyed web into predetermined lengths without interrupting the flow of web.

A further object of the present invention is to provide a control system making it possible to cut a web precisely on the marks which have been pre-printed thereon at a fixed or varying interval.

A still further object of the present invention is to provide a web cutting control system which facilitates the setting and change of the cutting length and permits such change even during operation.

The present invention consists in a web cutting control system which makes it possible to cut a web automatically, continuously and accurately either into digitally preset lengths or on the marks put thereon beforehand. These and other objects and advantages of the invention will become more apparent from the following description and drawings, in which:

FIG. 1 is a schematic illustration showing the operating principle of a conventional web cutting machine;

FIG. 2 is a schematic illustration, similar to FIG. 1, showing the operating principle of a web cutting control system embodying the present invention;

FIG. 3 is a schematic illustration showing the mounting position of three sensors relative to the rotary cutter;

FIG. 4 is a side view of the rotary cutter provided with the control system embodying the present invention;

FIG. 5 is front view of the rotary cutter of FIG. 4;

FIG. 6 is a block diagram of the control system embodying the present invention;

FIGS. 7a and 7b are wave form diagrams showing how the distance between the marks on the web is discriminated to be "long-size" or "short-size" in the fixed-position cutting.

FIGS. 8-12 are graphs showing how various signals change and are counted in each cutting cycle for fixed-position cutting; and

FIGS. 13-20 are similar graphs showing the same for constant-size cutting. The mechanical and electrical arrangements of a preferred embodiment of the present invention are shown in FIGS. 2-6.

A rotary cutter 3 has a pair of rolls coupled together by a pair of gears 1 and 2 for synchronous rotation. (FIG. 2) The main shaft 4 of the lower roll is provided with a reduction gearing 5 to which is coupled a DC motor 6. A tachometer generator 7 and a transducer PGB are connected to the other end of the DC motor 6 to detect the rotating angle of the rotary cutter 3. If the reduction gearing 5 has a reduction ratio of 4:1, for example, the rotary cutter 3 makes one revolution for each four revolutions of the motor 6. The transducer PGB, coupled directly to the motor 6, generates two different pulse sequences 90° out of phase from each other each at a rate of 600 pulses for each revolution thereof.

A wheel 8 is kept in contact with the web X to be cut with a sufficient pressure to be driven by friction. To the shaft 9 of the wheel 8 is coupled a transducer PGA to detect the length of the web which has been fed. The transducer PGA, too, supplies two different pulse sequences 90° out of phase from each other each at a rate of 3000 pulses for each revolution thereof.

As shown in FIG. 3, a sensor OPA (photoelectric tube) is provided at a distance l3 ahead of the cutting point P to detect the cutting marks which have been pre-printed on the web at predetermined or varying spacings in fixed-position cutting.

Another sensor OPC is provided at a position where the cutting blades have moved a peripheral distance L1 mm past the actual cutting point in the rotating direction, to detect completion of cutting and produce a web cutting completion signal C.

The reason why the sensor OPC for producing the cutting completion signal C is located not at the actual cutting point P but at l1 mm past the point P (FIG. 3) is that if the cutter 3 were stopped simultaneously upon completion of cutting, it would have its blades caught in the web. In order to avoid this, the cutter 3 is designed to stop only after if has cut the web and through an additional angle.

Also, at a peripheral distance l2 mm of the cutting point P along the periphery of the cutter 3 is located a third sensor OPB to detect the arrival of the tip of cutter blade to produce a mark distance discrimination signal.

Referring to FIGS. 4 and 5, the numeral 10 designates a frame; 11 are bearings for the rotary cutter 3; 12 is a cover for the gearing 5; 13 is a blower for cooling the motor 6; 14 are web feed rollers; and 15 is a fluid pressure cylinder for the wheel 8. The pressure at which the wheel 8 is pressed against the web X can be adjusted by means of the cylinder 15.

Referring to the block diagram of the control system shown in FIG. 6, a comparison unit 16 compares the value L0 preset on the cutting length setter LA (digital switch) with the value B0 preset on the reference pulse setter LB and feeds the difference therebetween (L0 -B0 =L), if any, to a counting circuit described later. The comparison unit 16 includes a reversible counter C1 which counts the preset value L0 from the cutting length setter LA, the comparator A1 which compares the content L0 of the counter C1 with the value B0 from the reference pulse setter LB to give any difference therebetween, and a gate GE E passes the difference signal in synchronization with the pulses from the pulse generator OSC. On the cutting length setter LA is set a desired cutting length in millimeters for constant-size cutting, or the distance between the cutting complete detection point and the mark detection point, that is, l1 +l3 mm (FIG. 3) for fixed-position cutting. On the reference pulse setter LB is set the number of pulses indicative of the circumference of the rotary cutter 3.

The numeral 17 designates an addition/subtraction discriminating circuit which compares the two preset values and couples the difference therebetween to the addition or subtraction input of the reversible counter C1 according to the result of the comparison. This circuit 17 includes a comparator A2 which compares the preset value L0 from the cutting length setter LA with the preset value B0 from the reference pulse setter LB to give an addition or subtraction command signal to a gate GD according to the result of comparison, and the gate GD which couples the signal fed from the gate GE back to the addition or subtraction input of the counter C1 in response to the command signal from the comparator A2.

A web flow detection circuit 18 detects the length of the web which has been fed to generate pulses, the number of which corresponds to the length. The circuit 18 includes the transducer PGA coupled to the wheel 8 in contact with the web, a pulse amplifier PA1 for amplifying the pulses generated by the transducer PGA, a phase discriminating circuit B1 for discriminating the rotating direction of the transducer PGA, and a constant multiplier D1 which multiplies the number of pulses by a constant.

The generation of pulses from the circuit 18 is accomplished in the following manner in the preferred embodiment. As described above, the transducer PGA supplies two different pulse sequences 90° out of phase from each other, each at a rate of 3,000 pulses for each revolution thereof. Since the wheel 8 has a circumference of 1,200 mm, the web runs for 1,200 mm while the wheel 8 makes one revolution. In order to generate pulses at a rate of one pulse for each 0.1 mm of the web length, the two pulse sequences are combined and [(3000+3000)×2] amplifier PA1 and the phase discriminating circuit B1. Thus, pulses, φA, are supplied from the constant multiplier D1 at a rate of 12,000 pulses for each revolution of the wheel 8 as a signal indicative of the web feed length.

A cutter rotating angle detection circuit 19 includes the transducer PGB coupled to the motor 6, a pulse amplifier PA2 a phase discriminating circuit B2 and a constant multiplier D2. In the preferred embodiment the constant multiplier D2 is set as follows: Because of the gear ratio of 4:1, the rotary cutter 3 makes one revolution for each four revolutions of the motor 6 and thus the transducer PGB. Since the rotary cutter 3 has a circumference of 864 mm, 8,640 pulses are required for each revolution thereof to produce pulses at the rate of one pulse for each 0.1 mm. For this purpose, two pulse sequences fed from the transducer PGB each at a rate of 600 pulses per revolution thereof are electrically combined and doubled as follows:

(600 PPR+600 PPR)×2=2,400 PPR

Thus, the number of pulses generated for four revolutions of the transducer PGB are 2,400 PPR×4=9,600 PPR. The constant multiplier D2 is set at 0.9 to convert this rate to 8,640 pulses per revolution of the cutter (8,640/9,600=0.9). Thus, 8,640 pulses produced as φB each time the transducer PGB makes four revolutions and the rotary cutter 3 makes one revolution.

The circuit configuration for fixed-position cutting will now be described. In this mode of cutting, the input signal (from a fixed-position cutting selector switch P.P) to the interface I1 is kept on.

First, it will be explained how the distance between the marks is discriminated to be long-size or short-size. The logic for discrimination is which first comes, the mark detection signal A or the cutting completion signal C, after the mark distance discrimination signal B has arrived. To put this in another way, any length longer or shorter than l1 +l3 (=L0) is discriminated to be long-size and short-size, respectively.

If first a cutting completion signal C and then a mark detection signal A comes after a mark distance discrimination signal B has been given as shown at (a) in FIG. 7, the control system will operate in the long-size cutting mode, in which an input signal discriminating circuit H0 supplies signal α1 to close the gate GA throughout from the completion of cutting to the detection of the next mark. Thus, only the signal φB is stored in the reversible counter C2 as a positive signal while signal φA is blocked at gate GA. When a mark detection signal A comes from the sensor OPA, the input signal discriminating circuit H0 momentarily supplies signal α2 and resets signal α1 to open the gate GA.

If first a mark detection signal A and then a cutting completion signal C are received after signal B, the control system will operate in the short-size cutting mode as shown at (b) in FIG. 7. In this mode, with a mark detection signal A, the input discriminating circuit H0 supplies signal α2 momentarily. From the arrival of a mark detection signal A to that of a cutting complete signal C, it also supplies signals α4 and α3 to keep the gate GC open and the gate GB closed, respectively. With a cutting completion signal C, signals α4 and α3 are reset to close the gate GC and open the gate GB.

The fixed-position cutting by the long-size cutting mode will be first described. When the interface I1 receives a mark detection signal A from the sensor OPA, the input discriminating circuit H0 supplies a preset signal α2 to cause the reversible counter C1 to store a value L0 (l3 mm+l1 mm) preset on the cutting length setter LA. The value L0 is compared by the comparator A1 with the value B0 (indicative of the circumference of the cutter 3) preset on the reference pulse setter LB. When L0 -B0 becomes negative, the output of the comparator A1 passes through the gates GE and GB in synchronization with the pulse from a reference pulse generator OSC. (The gate GE is designed to open when the output from the comparator A1 is other than zero, and close only when it is zero.) It is a fed through the synchronizer SN to the gates GD and GF.

On the other hand the comparator A2 also compares L0 with B0 and sends a command to couple the output of gate GD to the addition input of the reversible counter C1 as long as L0 -B0 <0, to feed the signal from the gates GE and GB back to the reversible counter C1 to add it to the value L0 stored therein.

As soon as the output from the comparator A1 becomes zero, the gate GE closes to stop the signal fed back to the counter C1. This means that the remainder L(L=L0 -BO) has been obtained by subtraction of the value B0 indicative of the circumference of rotary cutter 3 from the preset value L0.

The remainder thus obtained goes through the synchronizer SN to the gate GF which directs it through the OR gate GJ to the reversible counter C2 as a signal to be subtracted in coincidence with the signal fed from the comparator A2 on the condition that L0 -B0 <0.

Also, the output pulse φA from the web flow detection circuit 18 is fed through the synchronizer SN, gate GA and OR gate GJ to the reversible counter C2 as a signal to be subtracted. As shown in FIG. 8, the reversible counter C2 thus receives these two signals every minute both as a subtraction signal to obtain L-φA. On the other hand, as soon as one cutting operation is complete, pulses φB the number of which is proportional to the angle for which the rotary cutter 3 has rotated from the cutting completion detection point are applied as a signal to be added to the counter C2 through the synchronizer SN and the OR gate GI. Thus, the counter C2 performs the following operation or reversible counting:

(L-φ.sub.A)+φ.sub.B, or (L.sub.0 -B.sub.0)-φ.sub.A +φ.sub.B

These inputs are combined by the counter C2 as graphically shown in FIG. 8, in which the arrows AD and SU indicate the addition and subtraction directions, respectively. Also, MP stands for the mark detection point and CP for the point where one cutting operation has been just completed. (These designations are used with the same meaning in all of the similar figures.)

The result of operation by the reversible counter C2 is fed moment by moment through a digital/analog converter D/A to a function generator FG which outputs voltage, VC, shown in FIG. 9-a,

V.sub.C =ƒ(R)=ƒ[(L.sub.0 -B.sub.0)-φ.sub.A +φ.sub.B ]

As shown in FIG. 9-b, the output voltage VC is coupled to the operational amplifier OP which compares it with a voltage VA to determine the differential, V0 =VA -VC. The voltage VA comes from a frequency-voltage converter F/V to which is fed pulse signal φ1A proportional to the web running speed.

The output voltage V0 is applied to the comparator A3 to compare it with 0 volt to discriminate whether V0 =VA -VC <0 or ≧O. Because VC is negative in this mode, V0 =VA -(-VC)=VA +VC >0. Therefore, the voltage V0 is fed through the make contact CRa of the relay CR to the motor control circuit CO so that the DC motor 6 is accelerated.

As the equation V0 =VA +VC shows, the DC motor 6 rotates at a higher speed than the web feed speed by a value corresponding to VC. Therefore, the input signal, φB, the reversible counter C2 increases at a higher rathe than φA as shown in FIG. 8, although the former is a signal to be added and the latter a signal to be subtracted.

At the point SS in FIG. 9-b where VC =(L0 -B0)-φAB =0, that is, V0 =VA, the speed of the rotary cutter 3 comes into complete synchronization with the web feed speed with the next mark and the cutter blades aqually spaced away from the cutting point. The web and the cutter move on in this condition unless there is any change in the web feed speed and the cutter speed, so that the web will be cut precisely on the mark. The graphs in FIGS. 8, 9-a and 9-b are summarized in FIG. 10.

If the speed of the DC motor 6 for the rotary cutter 3 should become so high that (L0 -B0)-φAB is not zero any more but becomes positive, the speed command voltage V0 (=VA -VC) fed to the motor control circuit CO would not be equal to VA any more, but become smaller than VA proportional to the web speed. This means that the DC motor 6 decelerates until VC decreases to zero again.

Also, if the web feed speed should decrease, for example, φA would not increase so much as φB and (L0 -B0)-φAB and thus the output voltage VC would become positive with the voltage VA once again, which means that the speed of the rotary cutter 3 comes into synchronization with the web feed speed.

Upon completion of one cutting operation, a cutting completion signal C from the sensor OPC is fed into the interface I1. Simultaneously, the input discriminating circuit H0 supplies signal α1 to close the gate GA to cut off the pulses φA from the web flow detection circuit 18, and forcibly make inoperative the relay CR in the comparator A3 to restore the break contact CRb thereof to its open position.

Accordingly, the motor control circuit CO is connected to zero voltage through the delay circuit CT so that the motor 6 stops after a certain time. The rotary cutter 3 remains stopped until the next mark detection signal A arrives. The angle of rotation of the rotary cutter 3 from the completion of cutting to the actual stop thereof is stored in the reversible counter C2 as signal φB from the cutter rotating angle detection circuit 19.

The cutting cycle in the fixed-position cutting is illustrated by line f at a in FIG. 7, in which the vertical dotted lines show the cutting points. When the horizontal dotted line SL is reached, the cutter speed comes into synchronization with the web speed. At the level of solid line CL, the rotary cutter 3 stops. The graph shows that the rotary cutter 3 is intermittently operated in the long-size cutting mode.

Next, cutting control in the short-size cutting mode will be described where the mark detection signal A is followed by the cutting completion signal C as shown at b in FIG. 7. In this mode, signal flow in the control system is almost the same as in the long-size cutting mode except for the output signals from the input discriminating circuit H0 and the operation of the gates GB and GC responsive thereto. When the interface I1 receives first a mark detection signal A from the sensor OPA after it has received a mark distance discriminating signal B from the sensor OPB the input discriminating circuit H0 produces preset signals α2, α3 and α4. With signal α2, the value L0 preset on the setter LA is registered in the reversible counter C1 through the interface I2. Also, signal α4 opens the gate GC and signal α3 closes the gate GB.

From the value L0 stored in the counter C1 is subtracted the pulses φA fed through the gate GC from the web flow detection circuit 18 until the web is cut on the last mark and the cutting completion signal C comes into the system.

In other words, if the next mark is detected by the sensor OPA before the web cutting on the last mark is complete, the distance between the marks is discriminated to be less than l1 +l3 mm shown in FIG. 3. With signal A from the sensor OPA, the reversible counter C1 is set to subtract from the preset value L0 the length α which the web has run before the cutting completion signal C for the last mark enters. By performing this subtraction, the control system judges the web cutting size to be not L0 but Z(=L0 -α), the value Z being left in the counter C1.

During the subtraction operation, the result of subtraction is not fed to the reversible counter C2 because the gate GB has been closed by signal α3. The pulses φA and φB also continue to be fed to the cunter C2 through the gate GA and OR gate GJ, and the OR gate GI, respectively.

When the cutting completion signal C arrives from the sensor OPC, the signals α3 and α4 from the input discriminating circuit H0 disappear so that the gate GB opens whereas the gate GC closes. Operation thereafter is the same as in the long-size cutting mode except that the difference signal Z-B0, not L0 -B0, is fed through the gate GF.

In the short-size cutting mode, the rotary cutter 3 continues to be driven at a speed equal to, or higher than, the web feed speed without intermittent stop as shown in line f' at b in FIG. 7. Speed control in the short-size cutting mode is graphically illustrated in FIGS. 11 and 12.

Constant-size cutting, another object of the present invention, will now be described.

In this control mode, the fixed-position cutting selector switch P.P, coupled to the interface I1, is placed in its OFF position to shut out the signals A and B from the sensors OPA and OPB to keep the gates GA GB opened and the gate GC closed. Also, the web need not have marks placed thereon.

First, speed control will be explained in the case where the value L0 preset on the cutting length setter LA is larger than, or equal to, the value B0 on the reference pulse setter LB (L0 ≧B0). (In constant-size cutting, any desired cutting length may be set as L0 on the cutting length setter LA, through L0 =l1 +l3 mm in fixed-position cutting.)

Upon completion of cutting, the input discriminating circuit H0 supplies signal α2 in response to signal C from the sensor OPC. With signal α2 the preset value L0 on the cutting length setter LA is stored in the reversible counter C1 through the interface I2. The value L0 is compared by the comparator A1 with the value B0 preset on the reference pulse setter LB. Since L0 -B0 >0 the gate GE, to which is coupled the pulse generator OSC, opens to pass the output of the comparator A1 to the gate GB in synchronization with the pulse from the reference generator OSC.

On the other hand, the comparator A2 also compares L0 with B0 to couple the output of the gate GD to the subtraction input of the reversible counter C1 while L0 -B0 ≧0 to feed the output from the gate GE back to the counter C1 to subtract it from the content thereof. In time, L0 --B0 will become zero so that the gate GE closes to stop the feedback signal for subtraction. This means that in the meantime, the difference signal L=L0 -B0 has been fed through the gates GE and GB toward the counter C2. It is fed from these gates through the synchronizer SN to the gate GF, which in response to the signal fed from the comparator A2 on the condition that L0 -B0 ≧0 directs it through the OR gate G1 into the reversible counter C2 as a signal to be added.

On the other hand, the pulses φA from the web flow detection circuit 18 are applied through the synchronizer SN, gate GA and OR gate GJ to the counter C2 as a signal to be subtracted. They are fed at a rate of one pulse for each 0.1 mm of web length as described above. Also, as the rotary cutter 3 rotates, the pulses φB corresponding to the rotating angle thereof from the cutting completion point are supplied through the synchronizer SN and the OR gate G1 to the counter C2 as a signal to be added. Thus, the counter C2 performs the following operation or reversible counting: (L0 -B0)-φAB.

These inputs are synthesized in the counter C2 as graphically illustrated in FIG. 13.

The result of operation by the counter C2 is fed by the minute through the digital/analog converter D/A to the function generator FG, the output of which VC =ƒ(R)=ƒ[(L0 -B0)-φAB ] is shown in FIG. 14.

As in fixed-position cutting, the output voltage VC is applied to the operational amplifier OP, which determines the differential V0 between it and voltage VA from the frequency/voltage converter F/V (V0 =VA -VC).

The resultant output voltage V0 is fed to the comparator A3 to compare it with 0 volts to discriminate whether V0 =VA -VC <0 or ≧0. If V0 is negative, the relay CR will not be actuated with the make contact CR.sub.α open as shown in FIG. 6 to block the input to the motor control circuit CO. If V0 is positive, the relay CR will be actuated, the make contact CR.sub.α being closed to input the voltage V0 from the operational amplifier OP to the motor control circuit CO.

Since L0 -B0 is positive and thus the voltage VC is larger than VA at the cutting completion point, the output of the operational amplifier OP (V0 =VA -VC) is negative so that the DC motor 6 is at standstill. As the web further runs with pulses φA increasing, the output, VC, from the frequency generator FG decreases until it becomes equal to VA and thus V0 becomes zero (FIG. 15), when the relay CR is actuated.

From then on, the motor 6 is made to run through the control circuit CO to drive the rotary cutter 3, pulses φB corresponding to the rotating angle thereof being fed again from the rotating angle detection circuit 19 through the synchronizer SN and the OR gate Gt to the reversible counter C2 as an addition signal. Since the pulses φB are smaller in number than the pulses φA indicative of the web feed length at this early stage, the output voltage V0 from the operational amplifier OP increases to accelerate the DC motor 6 rapidly until the cutter speed follows the web feed speed.

At the point where (L0 -B0)-φAB becomes zero, the rotary cutter speed will come into complete synchronization with the web feed speed with the cutter blades and the point of the web at which it is to be cut equally spaced from the cutting point. This condition remains unchanged unless there is any further change in the cutter speed or the web speed, so that the web is cut into a predetermined size L0. FIG. 16 summarizes the graphs shown in FIGS. 13 to 15.

If there should be any change in the cutter or web speed, the cutter will be brought back to synchronization with the web feed speed in quite the same manner as in fixed-position cutting.

The manner in which the cutter speed is controlled will not be described in the case where the preset value L0 on the cutting length setter LA is smaller than the preset value B0 on the reference pulse setter LB (L0 -B0 <0).

In this case, too, signal flow in the control system is almost the same as in the above-mentioned case (L0 -B0 ≧0), but the gates GD and GF operate differently according to the result of discrimination by the comparator A2.

With signal α2, the preset value L0 on the cutting length setter LA is stored in the reversible counter C1 through the interface I2. The comparator A1 compares L0 with B0 to discriminate L0 -B0 <0. Accordingly, the gate GE opens to pass the output of the comparator A1 to the gate GB in sychronization with the pulse from the reference generator OSC.

On the other hand, the comparator A2 also compares L0 with B0 to couple the output of the gate GD to the addition input of the reversible counter C1 while L0 -B0 <0 to feed the signal from the gate GE back to the counter C1 to add it to value L0 therein. In time, L0 -B0 becomes zero so that the gate GE closes to stop the feedback signal for addition. This means that the difference signal L=L0 -B0 has been fed from the gates GE and GB toward the counter C2. It is fed from these gates through the synchronizer SN to the gate GF which in response to the signal fed from the comparator A2 on the condition that L0 -B0 <0 directs it through the OR gate GJ into the reversible counter C2 as a signal to be subtracted.

In the meantime, as in the case where L0 -B0 ≧0, pulses φA from the web flow detection circuit 18 are supplied to the counter C2 as a subtraction signal, and pulses φB rom the rotating angle detection circuit 19 as a addition signal. Thus, the counter C2 performs the following operation: (L0 -B0)-φAB.

As in the above described case, the result of operation by the counter C2 is fed by the minute through the digital/analog converter D/A and the function generator FG to the operational amplifier OP, the output V0 of which is compared with volts at the comparator A3.

Because VC is negative in this case, V0 =VA -(-VC)=VA +VC >0. Therefore, the voltage V0 is applied through the make contact CR.sub.α of the relay CR to the motor control circuit CO to accelerate the DC motor 6. As the equation V0 =VA +VC shows, the DC motor 6 rotates at a higher speed than the web feed speed by VC. Therefore, the input signal, φB, to the reversible counter C2 increases at a higher rate than φA as shown in FIG. 17, although the former is a signal to be added and the latter a signal to be subtracted.

At the point SS in FIG. 19 where VC =(L0 -B0)-φAB =0, that is, V0 =VA, the speed of the rotary cutter 3 comes into complete synchronization with the web feed speed with the cutter blades and the point at which the web is to be cut equally away from the cutting point. The rest is the same as in the above described case (L0 -B0 ≧0). The graphs in FIGS. 17 to 19 are summarized in FIG. 20.

The present invention makes possible continuous, automatic cutting of the web on the marks thereon or into predetermined lengths by means of the abovementioned arrangement. The control system embodying the present invention has the following advantages over the conventional control systems described at the beginning of the specification:

1. The length into which the web is to be cut is manually set on a digital switch. This setting may be readily and instantaneously changed even during operation without producing any appreciable material loss.

2. Electronic control by means of digital and analog control systems provides high accuracy with a minimum of cutting error and makes possible control of the cutting length setting by any external signal (from an electronic computer, for example).

3. The speed of a rotary cutter used is electronically brought into synchronization with the web feed speed and kept in such a state until the instant of cutting. This assures not cutting error and provides an extremely simple mechanical arrangement compared with the prior art system in which this synchronization was achieved by mechanical means. Directly coupled to a DC motor through a gearing, the rotary cutter has a driving which is very simple in construction.

4. The web is cut by detecting the marks pre-printed thereon by means of a mark detection sensor. Therefore, independently of the size between the marks, the web is cut precisely on the marks.

5. If there should arise any change in the web feed speed, the control system causes the rotary cutter to follow it automatically because the web feed speed is converted to a voltage for use as a reference voltage. Such a change cannot, therefore, interfere with precise cutting.

6. The electronic control system with extremely simple mechanical construction provides noiseless, stable cutting control.

7. Three sensors are provided to discriminate the distance between the marks to be long-size or short size according to the order in which signals come thereform. This assures that independently of the distance between the marks, the web is precisely cut on the marks.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3181403 *Aug 3, 1962May 4, 1965Logic Systems IncControl system
US3604300 *Jun 24, 1969Sep 14, 1971Cutler Hammer IncFrequency base knife control systems
US3668957 *Aug 8, 1969Jun 13, 1972Koppers Co IncSheet length control system
US3706248 *Jan 4, 1971Dec 19, 1972Cincinnati IncNumerical control apparatus for a shear
US3730810 *Jun 15, 1971May 1, 1973Eickhoff GebCorrugated paperboard cutting apparatus
US3870936 *May 25, 1972Mar 11, 1975Hurletron IncDigital motor control system for web registration
US3873899 *Nov 9, 1973Mar 25, 1975Komatsu Mfg Co LtdAutomatic index and operating cycle regulator for a punch
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5286317 *Aug 9, 1991Feb 15, 1994Computyre Inc.Rotary die cutting mechanism
US7004053Mar 15, 2000Feb 28, 2006Kimberly-Clark Worldwide, Inc.System for measuring and controlling cut length of discrete components in a high-speed process
Classifications
U.S. Classification318/600, 318/603, 83/74, 83/371, 700/167
International ClassificationB23D36/00
Cooperative ClassificationY10T83/543, B23D36/005, Y10T83/148
European ClassificationB23D36/00B13B2