GB2276957A - Automatic variable speed anvil system for rotary die-cut apparatus - Google Patents

Description

2276957 1 1 2 3 6 7 8 9 10 12 14 is 19 20 21 22 23 24 25 26 27 28 29 30 31

32 33 34 35 36 37 38 Automatic Variable Speed Anvil System for Rotary Die-cut Apparatus This invention relates particularly to rotary die-cut apparatus, particularly for die-cutting sheets of corrugated board and the like in the production of carton blanks. In particular, the invention relates to control of the rotary speed of the anvil roll relative to the die roll in order to accommodate changes in the anvil roll diameter as a result of normal use.

In rotary die-cut apparatus, typically forming a section of a flexographic printer/die-cutter machine, a die roll carrying one or more die blades cuts corrugated board blanks against a supporting anvil roll. The corrugated board blanks are fed successively through a nip formed between the cooperating die and anvil rolls. Both the die and anvil rolls are rotatably driven. The anvil roll is typically driven via a gearing arrangement from the die roll: that is, the drive for the anvil roll is mechanically coupled to the drive for the die roll. The anvil roll commonly has a resilient cover or blanket, typically of a urethane or polyurethane material, into which the blades of the die roll penetrate during the die-cutting of the blanks. As used herein, the term "diecutting" includes scoring the blanks, to form fold lines, and/or making complete cuts through the blanks.

Usually, the die blades are serrated, and the penetration of the serrated die blades repeatedly into the resilient cover tends, over time, to cut and tear the surface of the cover. It then becomes necessary to replace the cover. As a result of normal wear, the cover surfaces becomes irregular, and the overall diameter of the covered anvil roll decreases.

The anvil roll is typically mounted in the frame of the machine such that it can be adjustably moved toward the die roll as the anvil roll cover wears, in order to provide for proper penetration of the die blades into the cover. In addition, arrangements have been proposed and attempted for rotating the anvil roll at a slightly different speed of rotation relative to the die roll. One such arrangement is the so-called "one tooth hunting ratio", whereby the die and anvil rolls are rotationally interconnected by a pair of gears, one of them having one gear tooth less than the other. For example, the die roll gear may have 101 teeth, an the anvil roll gear 100 teeth. In that way, the pattern of penetration of the die blades into the anvil roll cover only begins to repeat after 100 2 1 4 6 7 8 9 11 12 13 14 16 19 22 23 24 26 27 28 29 30 31 32 33 34 37 IYH/7346 revolutions of the anvil roll. This slows down the wear rate of the anvil roll cover. However, because the rolls usually rotate at more than 100 rpm, the pattern of penetration of the die blades into the anvil roll cover occurs fairly frequently.

As an attempt to solve that problem, anvil roll cover trimmers have been developed to extend the life of the anvil roll cover and improve product quality by trimming the anvil roll cover surfaces that have deteriorated from normal use to restore them to a usable condition. This can extend anvil roll cover life in addition to providing longer anvil roll cover life by using anvil roll covers which are thicker than anvil roll covers used on standard die cutters. A trimming tool comprising a knife blade is provided adjacent the anvil roll. When resurfacing of the anvil roll cover is to be carried out, the trimming tool is brought into contact with the anvil roll cover and, as the anvil rotates, the trimming tool is moved axially along the anvil roll cover, in the manner of a lathe. The trimming tool can thus restore the surface of the anvil roll cover to a uniform diameter. By trimming the anvil roll covers regularly and keeping the anvil roll surface more nearly uniform, the quality of scoring and die-cutting is improved as a result of the more uniform depth of penetration of the die blades into the anvil roll cover. On machines not equipped with anvil roll cover trimmers, excessive amounts of die blade penetration are required in areas that are not worn in order to provide adequate penetration in areas that are worn.

An inherent result of the die cutting process and the trimming process is that the overall diameter of the covered anvil roll decreases, particularly after each trimming operation. It is therefore necessary to move the anvil roll closer to the die roll in order to obtain the desired amount of die penetration. This may be done by journaling the anvil roll for rotation within eccentric housings so that rotation of the eccentric housings will enables the anvil roll to be moved toward or away from the die roll.

A more difficult problem resulting from the trimming operation is that, as the overall diameter of the covered anvil roll decreases, the tangential velocity at any point on its surface decreases, assuming a constant rotational speed. The tangential velocity is in fact directly proportioned to the diameter of the roll.

The net result is that the tangential velocity of the anvil roll will decrease relative to the tangential velocity of the die roll, unless some :X 3 6 7 8 12 14 is 16 17 19 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 IYH/7346 provision is made for increasing the rotational speed of the anvil roll to compensate for its decrease in diameter. If no such provision is made, board blanks travelling through the nip between die roll and anvil roll will experience a differential in linear speed between their upper and lower surfaces. This results in slippage and unsatisfactory die cutting, including tearing, ragged cuts, and cuts not within desired dimensional tolerances.

Prior attempts at solving the problem of adjusting the rotational speed of the anvil roll to compensate for anvil trimming operations have relied on complex mechanical gearing arrangements between the die roll and the anvil roll. As an example, U.S. Patent 4,736,660 discloses a rotary die- cut apparatus and a gearing arrangement which uses a harmonic drive in a gear train between the anvil and die rolls. Random speed changes are made to an adjustment motor having a rotary input into the harmonic drive in order to temporarily change the gear ratio of the harmonic drive. That patent also discloses providing a gear train between the die and anvil rolls with a plurality of pairs of gears of different gear ratios to provide a very long period between repeats of die blade penetration patterns into the anvil roll cover.

That patent goes on to disclose adjusting the peripheral speed of the anvil roll to that of the die roll by sensing the diameter of the anvil roll and mechanically changing the gear ratio between the anvil and die rolls based on the sensed diameter change of the anvil roll. The patent discloses using sonar to sense the position of the surface of the anvil roll cover, or sensing the position of the anvil roll cover by physical contact, or by sensing the position of the rotational axis of the anvil roll after moving it relative to the die roll for desired die penetration.

The solutions proposed by patent 4,736,660 are cumbersome to say the least. The gearing arrangements provided for in that patent are exceedingly complex, require precise adjustment, and are susceptible to misalignment, wear, slippage and backlash in the gear train, and a host of other practical limitations.

The present invention aims to provide a unique solution to the problem of compensating for decreases in the overall diameter of a covered anvil roll as a result of wear and trimming without having to suffer at least some of the drawbacks of prior systems. The present invention does so by physically decoupling the anvil roll from the die roll and driving the anvil roll independently of the die roll. The rotational 4 1 3 4 5 6 7 8 9 11 12 14 16 21 26 28 29 31 32 33 34 36 37 38 IYH/7346 speed of the die roll and the overall diameter of the covered anvil roll are sensed and are used to control a separate drive motor coupled to the anvil roll which rotates the anvil roll at an appropriate rotational speed so that the tangential velocities of the die roll and anvil roll will be substantially the same. This minimises any differential velocity experienced by board blanks moving between the die and anvil rolls, and provides an infinitely variable hunting ratio to distribute wear more uniformly around the entire circumference of the anvil roll.

The present invention enables the use of thicker anvil roll covers, allowsing for a significant number of anvil trimming operations.

According to one aspect of this invention, apparatus for controlling the rotational speed of a second rotating member of variable diameter (e.g. an anvil roll) relative to a first rotating member of constant diameter (e.g. a die roll) comprises means for rotating the first member about an axis at a first desired rotational speed, first sensing means for sensing an actual rotational speed of the first member, second sensing means for sensing an actual diameter of the second member or a related measurement (such as the position of the anvil roll after it has been moved to restore the appropriate cooperative relationship between the rolls after trimming of the anvil roll), control means responsive to both first and second sensing means for generating a drive signal for driving the second member at a second desired rotational speed which is a function of the actual rotational speed of the first member, and drive means responsive to the drive signal from the control means for driving the second member at the second desired rotational speed.

An example of apparatus according to this invention is shown in the accompanying drawings.

Figure 1 is a side elevational view, partially in section, illustrating a die-cut apparatus employing the present invention.

Figure 2 is a sectional view taken along the line 2-2 in Figure 1, showing details of the die-cut apparatus of Figure 1.

Figure 3 is a sectional view taken along the lines 3-3 in Figure 2, showing one of the eccentric bearings in which the anvil roll is journaled.

Figure 4 is a sectional view taken along the lines 4-4 in Figure 2, showing details of the means for sensing the rotational speed of the die roll and the means for sensing the overall diameter of the anvil roll.

Figure 5 is a sectional view taken along the lines 5-5 in Figure 4, showing a coupling between die roll and the means for sensing die roll 9 1 1 2 3 4 5 6 7 a 9 11 13 14 is 16 17 is 19 22 26 27 28 29 31 32 33 34 36 37 38 IYH/7346 velocity.

Figure 6 is a simplified block diagram of a servo control system for controlling the rotational speed of the anvil roll in response to the means for sensing the rotational speed of the die roll and the means for sensing the overall diameter of the anvil roll.

Referring now to the drawings, Figure 1 illustrates, in a very simplified manner, a side view of a rotary die-cut apparatus 10 which typically forms a section of a flexographic printer or flexo/folder/gluer machine typically used in the manufacture of corrugated cartons. (While the invention is described in connection with a machine for manufacturing corrugated cartons, it should be understood that the invention is not limited to the manufacture of any particular product, or to any particular machine.) Die-cut apparatus 10 comprises an upper die roll 12 and a lower anvil roll 14 which operate on a corrugated board blank 16 passing through the nip between die roll 12 and anvil roll 14. Blanks 16 are fed to the die roll 12 and anvil roll 14 by a feed roll 18, in known manner. An anvil roll cover trimmer, designated generally by reference numeral 20, is provided for trimming the anvil roll cover 22, in order to resurface the anvil roll cover 22 and restore a uniform diameter to the covered anvil roll 14. In conventional fashion, trimmer 20 moves axially along the outer surface of anvil roll 14 along a guide rod 24, which extends transversely across die-cut apparatus 10, when trimming anvil roll cover 22. Trimmer 20 is provided with a trimming blade or knife 26 which removes a desired amount of anvil roll cover 22. Anvil roll cover trimmer 20 is known in the art, and need not be described in greater detail here.

Referring now to Figures 2 and 3, in addition to Figure 1, die roll 12 is journaled for rotation in bearings 28 and 30 mounted in side frames 32 and 34. Die roll 12 comprises a metal cylinder mounted on shafts 36 and 38. One or more scoring dies 40 and cuffing dies 42 are mounted on die roll 12, each die comprising scoring or cutting blades extending radially from the die roll 12. The die roll 12 is driven by a die roll drive gear 44, which is coupled to the main drive (omitted for clarity) of the flexographic printer.

Anvil roll 14 is journaled for rotation below die roll 12, and is located so that the scoring and cutting dies 40 and 42 may penetrate anvil roll cover 22 when cutting or scoring a corrugated board blank 16. Anvil roll cover 22 may be formed as a continuous cylinder, or may 6 1 2 3 4 6 7 8 9 11 12 13 14 15 16 17 is 19 21 22 23 24 25 26 28 38 IYH/7346 comprise a plurality of annular sections, mounted on (and removable from) the circumference of anvil roll 14. Preferably, anvil roll cover 22 is a urethane or polyurethane material.

Anvil roll 14 includes two axially extending shafts 46 and 48 by means of which anvil roll 14 is journaled for rotation between side frames 32 and 34 in eccentrics 50 and 52. Eccentrics 50 and 52 are mounted to gears 54 and 56, and are affixed thereto by clamp plates 58 and 60. Both eccentrics 50 and 52 are adjustably rotatably mounted in bores in the respective side frame 32 and 34. Rotational adjustment of the eccentrics 50 and 52 moves anvil roll 14 upwards or downwards to obtain the correct distance between die roll 12 and anvil roll 14. To that end, eccentrics 50 and 52 are adjustable by means of a manual adjustment system 62. Adjustment system 62 includes a handwheel 64 and a set of adjustment gears 66, 68, 70 and 72 which intermesh and permit gears 54 and 56 to be rotated by rotating hand wheel 64. An anvil roll position indicator 74 is also driven by handwheel 64 through intermediate gears 76 and 78. Rotation of handwheel 64 thus causes the rotation of an indicating dial 80 relative to a fixed pointer 82.

Although the details of the anvil roll adjustment system are not crucial to the invention, it can be seen that rotation of handwheel 64 results in the rotation of gear 66 which is mounted on a common shaft 84 with handwheel 64. Gear 66 meshes with gear 68, which is mounted on a common shaft 86 with gears 70 and 72. Thus the rotation of handwheel 64 is transmitted to gears 70 and 72 through gears 66 and 68 and shaft 86. Gears 70 and 72 mesh with gears 54 and 56, causing them to rotate in the same direction. As best seen in Figure 1, the axis of the eccentrics 50 and 52 is spaced apart from the axis of anvil roll 14, so that rotation of gears 54 and 56 results in movement of anvil roll 14 toward or away from the die roll 12.

As previously described, die roll 12 is driven by the main machine drive Via a gear 44 on die roll shaft 38. The rotational speed of die roll 12 is sensed by a shaft encoder 88 coupled to die roll shaft 36. As best seen in Figures 4 and 5, shaft encoder 88 is coupled to die roll shaft 36 via a 1:1 gear coupling 90. Gear coupling 90 comprises a gear 92 mounted for rotation with shaft 36, and a meshing gear 94, mounted for rotation with a shaft 96 which is coupled to the shaft encoder 88. Shaft 96 is preferably journaled for rotation in bearing 98. Gear coupling 90 is enclosed in a housing 100. By virtue of the 1:1 gear coupling 90, one 7 1 2 3 4 5 6 7 9 10 11 12 13 14 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 IYH/7346 complete revolution of die drum 12 will produce one complete revolution of shaft 96 of shaft encoder 88. In the illustrated embodiment, the shaft encoder will produce 5000 pulses for each complete revolution. The output pulses from shaft encoder 88, which represent the rotational speed of die roll 12, are used to drive anvil roll 14 as will be described below.

Anvil roll 14 is mechanically separate from both die roll 12 and the main drive of the machine. It is independently driven by an electric motor 102 (Figure 2). Motor 102 is mounted on the outside of a drive housing 104 which encloses a coupling arrangement for coupling the output shaft 106 of motor 102 to anvil roll shaft 46. The coupling arrangement is similar to an Oldham drive. As best seen in Figure 4, output shaft 106 of motor 102 is keyed via a key and slot arrangement 108 to an elongated plate 110. The opposite ends of elongated plate 110 carry roller assemblies 112 and 114, which are received in U-shaped slots 116 and 118 in a generally circular slotted plate 120. As best seen in Figure 4, slotted plate 120 has U-shaped slots at 900 intervals around its circumference. Roller assemblies 112 and 114 are received in diametrically opposite slots 116 and 118. A second set of diametrically opposite slots 122 and 124 are located perpendicularly to slots 116 and 118. Slots 122 and 124 receive a pair of roller assemblies 126 and 128 which are mounted on a second generally elongated plate 130. Plate 130 is mounted for rotation with anvil roll shaft 46.

As can be seen, rotation of output shaft 106 of electric motor 102 imparts rotational movement to plate 110 which is keyed to shaft 106. The rotational movement of plate 110 is imparted to slotted plate 120 through roller assemblies 112 and 114 in engagement with slots 116 and 118. In turn, rotation of slotted plate 120 imparts rotational movement to plate 130 through slots 122 and 124 which receive roller assemblies 126 and 128. Since plate 130 is mounted for rotation with anvil roll shaft 46, rotational movement is ultimately imparted to anvil roll 14. It will be appreciated that the drive arrangement coupling motor 102 with anvil roll 14 does not require precise alignment between the axis of motor shaft 106 and anvil roll shaft 46. On the contrary, the coupling arrangement accommodates movement of anvil roll shaft 46 as anvil roll 14 is moved toward and away from die roll 12 when adjusting the relative spacing between die roll 12 and anvil roll 14. The coupling arrangement also accommodates axial movement of the anvil roll relative to motor 102.

8 1 2 3 4 6 7 a 9 11 12 13 14 16 is 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 IYH/7346 The position of anvil roll 14 relative to die roll 12 is sensed electronically by means of a displacement transducer 132, which may be linear displacement transducer (LDT) or any other displacement transducer. One end 134 of transducer 132 is fixed to side frame 32 via a bracket 136, for example. The opposite end 138 of transducer 132 is attached to the free end 140 of an arm 142 which is pivoted at its other end about a boss 144, also on side frame 32. Mounted on the freed end 140 of arm 142 is a cam follower 146 which rides on the outer circumference of a cam disk 148. Cam disk 148 is mounted on eccentric 54 and is mounted to be coaxial with the axis of anvil roll 14. Thus, as the position of anvil roll 14 is adjusted relative to die roll 12 by rotation of eccentric 54, cam disk 148 will move toward or away from die roll 12. As it does, arm 142 will move, transmitting the movement to displacement transducer 132. The displacement sensed by transducer 132 is thus representative of the position of anvil roll 14 and, hence, is representative of the diameter of anvil roll 14, assuming that the position of the anvil roll has been correctly adjusted, after trimming, to restore the correct cooperative relationship between the die roll and the periphery of the anvil roll. The output signal of transducer 132 can be processed along with the output signal from shaft encoder 88 to provide drive signals for electric motor 102, so that electric motor 102 can drive anvil roll 14 at the appropriate rotational speed so that the surface velocity of the anvil roll 14 will match the surface velocity of die roll 12, as will now be described.

Figure 6 illustrates in simplified block diagram form one embodiment of a servo control circuit for controlling the rotational speed of the anvil roll in response to inputs representing the rotational speed of the die roll and the overall diameter of the anvil roll. Before describing the circuit illustrated in Figure 6, it should be mentioned that the precise circuitry for controlling the rotational speed of the anvil roll is not the crucial feature of the invention. That is, any number of ways of processing the sensor signals from the transducer 132 and the shaft encoder 88 can be used without departing from the scope of the invention. For example, the circuit of Figure 6 can be implemented in discrete circuit components, i.e., in hardware, or can be implemented in a microprocessor or other type of programmable controller, i.e., in software.

Referring now to Figure 6 in more detail, the rotational speed of the anvil roll is controlled by servo system 150 in response to inputs from 9 1 3 6 7 8 9 10 11 12 13 14 17 18 19 20 21 22 23 24 25 26 27 28 29 32 33 34 IYH/7346 the transducer 132 and the encoder 88 coupled to the die roll. In Figure 6, transducer 132 is represented by LDT block 152 and encoder 88 is represented by MASTER ENCODER block 154. The output of the servo system 150 is used to control the rotational speed of motor 102 coupled to the anvil roll. Motor 102 is represented in Figure 6 by ANVIL DRIVE MOTOR block 156.

In operation, as already described, die roll 12 is rotationally driven via drive gear 44, and is coupled to the encoder 154 as represented in Figure 6. Thus, as the die roll rotates it causes encoder 154 to produce output pulses, in known manner, which represent the rotational movement of die roll 12. Preferably, although not necessarily, encoder 154 is a 5000 line encoder (such as a Dynapar 5000 line direct read encoder, for example) coupled to die roll 12 via 1:1 gear coupling such that one revolution of die roll 12 results in 5000 output pulses from encoder 154. The number of output pulses from encoder 154 per unit of time will be representative of the rotational speed of the encoder and, hence, the rotational speed of die roll 12. The output pulses from encoder 154 form one input to servo system 150, as seen in Figure 6. Servo system 150 is preferably, although not necessarily, a digital system.

A second input to servo system 150 is a signal from transducer 152. Preferably, transducer 152 is an LDT or other suitable displacement transducer and, as such, outputs an analog signal. In that event, the analog output signal from transducer 152 is first processed in an analogto-digital (A/D) conversion circuit 158, so that the input to servo system 150 will be appropriately digital in form. As described previously, the output of transducer 152 is a signal representative of the overall diameter of anvil roll 14.

With signals representative of the rotational speed of the die roll 12 and the overall diameter of the anvil roll 14, it is a simple matter to derive a control signal for drive motor 156 so that motor 156 drives anvil roll 14 at the appropriate rotational speed so that the surface velocity of anvil roll 14 will be the same as the surface velocity of die roll 12.

A typical die roll may have an initial radius of 10.5 inches and may have an angular velocity of, for example, 100 revolutions per minute (rpm). Its surface velocity is therefore 10.5 x 100 x 21r inches per minute: about 9.16 feet/second. However, suppose that the radius of the anvil roll has decreased as the result of a trimming operation in which the 1 2 3 4 6 8 11 14 16 17 18 19 27 29 31 32 33 34 36 37 IYH/7346 surface of the anvil roll cover 99 has been removed, leaving a radius of 10.25 inches. (it is to be remembered that all numerical values given are exemplary only in order to illustrate the operation of the invention, and are not necessarily identical to numerical values that will be encountered in practice.) In that case, in order to restore the anvil roll surface velocity to 9.16 ft/s, it is necessary to increase the anvil roll speed by the ratio of 10.5:10.25; i.e. to about 102.5 rpm.

In the servo system 150 illustrated in Figure 6, the pulses from encoder 154 are counted to derive a rotational speed of the die roll. This rotational speed is used to derive the rotational speed at which the anvil roll should be driven in order for it to have substantially the same surface velocity as the die roll. At the same time, the signal from transducer 152 is processed to derive a figure for the radius of the anvil roll. Based on that, an appropriate rotational speed can be represented by a train of output pulses from servo system 150 to anvil drive motor 156, which will cause anvil drive motor to rotate at the required speed. That speed may or may not be equal to the rotational speed at which the anvil roll is to rotate. If the anvil drive motor is to be driven at a different rotational speed, a suitable ratio coupling can be used so that the rotational speed of the anvil roll is as desired. A tachometer 160 on anvil drive motor may be provided to close the inner loop of servo system 160 by feeding back a signal representative of the rotational speed of anvil roll 14 to servo system 150. This permits tight speed control of drive motor 156 and minimises servo oscillation.

In addition, a slave encoder 162 is preferably coupled to drive motor 156, and the signal from the slave encoder 162 is fed back to servo system 150. This feedback forms the outer loop of the servo and serves to synchronise the rotational position of the anvil roll 14 with the rotational position of the die roll 12. Thus, servo system 150 matches the rotation of the anvil roll 14 to the rotation of the die roll so that they rotate in synchronism, just as though anvil roll 14 were mechanically coupled to die roll 12. It will be appreciated by those skilled in the art that the servo system of the present invention is more than just a speed control servo, and includes position control so that the rotational position of the anvil roll relative to the rotational position of the die roll can be controlled.

A feature of the invention is that servo system 150 can provide for fine adjustments in the ratio of the rotational speed of the anvil roll to the rotational speed of the die roll, by adjusting the frequency of the output 1k 11 1 2 3 4 6 7 8 9 11 12 13 14 is 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 IYH/7346 pulses from servo system 150 to anvil drive motor 156. At a given machine speed and anvil roll diameter, ideally there will be a fixed ratio between the rotational speeds of the anvil roll and the die roll. It is this ratio that may be varied by the fine adjustment feature to compensate for inevitable differences in manufacturing tolerances.

Another feature of the invention is that the servo system readily compensates for small difference in overall anvil roll diameter around the circumference of the anvil roll as it rotates. Such differences result from inevitable differences in anvil roll cover thickness at different locations of the anvil roll.

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Claims (10)

Claims

1. Apparatus for controlling the rotational speed of a second rotating member of variable diameter relative to a first rotating member of constant diameter, comprising means for rotating the first member about an axis at a first desired rotational speed, first sensing means for sensing an actual rotational speed of the first member, second sensing means for sensing an actual diameter of the second member or a related measurement, control means responsive to both first and second sensing means for generating a drive signal for driving the second member at a second desired rotational speed which is a function of the actual rotational speed of the first member, and drive means responsive to the drive signal from the control means for driving the second member at the second desired rotational speed.

2. Apparatus for controlling the circumferential surface velocity of a second rotating member of variable diameter relative to the circumferential surface velocity of a first rotating member of constant diameter, comprising drive means for driving the first rotating member about an axis at a preselected rotational speed to impart to the first rotating member a first desired circumferential surface velocity, first sensing means for sensing an actual rotational speed of the first rotating member, second sensing meeans for sensing an actual diameter of the second rotating member or a related measurement, control means responsive to both first and second sensing means for (a) deriving from the actual rotational speed of the first rotating member an actual circumferential surface velocity of the first rotating member, (b) determining from the actual circumfential surface velocity of the second rotating member a desired rotational speed for the second rotating member which will result in a circumferential surface velocity of the second rotating member substantially equal to the actual surface velocity of the first rotating member, and (c) generating a drive signal for driving the second rotating member at the desired rotational speed, and drive means responsive to the drive signal from the control means for driving the second rotating member.

3. Die-cutting apparatus, comprising: a die roll and an anvil roll having a cover thereon, the die roll and anvil roll being rotatable 1 1 13 1 3 4 6 7 8 9 11 12 13 14 Is 16 17 18 19 21 22 23 24 26 27 29 32 33 34 36 37 38 IYH/7346 about mutually parallel and spaced-apart axes; means for rotating the die roll about its axis at a first desired rotational speed; encoder means for sensing an actual rotational speed of the die roll; transducer means for sensing an actual diameter of the anvil roll or a related measurement; control means responsive to the encoder means and the transducer means for generating a drive signal for driving the anvil roll at a second desired rotational speed which is a function of the actual rotational speed of the die roll and the actual diameter of the anvil roll; and drive means responsive to the drive signal from the control means for driving the anvil roll at the second desired rotational speed, whereby both the die roll and the anvil roll have substantially equal circumferential surface velocities.

4. Die-cutting apparatus according to claim 3, further comprising second encoder means for sensing rotational position of the anvil roll and feeding back a signal representative of the rotational position of the anvil roll to the control means for modulating the drive signal from the control means to synchronise the rotational position of the anvil roll with the rotational position of the die roll.

5. Die-cutting apparatus according to claim 3 or claim 4, further comprising tachometer means for sensing an actual rotational speed of the anvil roll and feeding back a signal representative of the actual rotational speed of the anvil roll to the control means for maintaining the actual rotational speed of the anvil roll substantially equal to the second desired rotational speed.

6. Die-cutting apparatus according to any one of claims 3 to 5, wherein the transducer means comprises a displacement transducer.

7. Die-cutting apparatus according to any one of claims 3 to 6, wherein the control means comprises a servo.

8. Die-cutting apparatus according to any one of claims 3 to 7, wherein the control means further comprises means for manually adjusting the ratio of the second rotational speed to the first rotational speed.

9. Die-cutting apparatus, comprising: a die roll and an anvil 14 1 3 4 6 7 8 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 IYH/7346 roll having a cover thereon, the die roll and anvil roll being rotatable about mutually parallel and spaced-apart axes; means for rotating the die roll about its axis at a first desired rotational speed; encoder means for sensing an actual rotational speed of the die roll; displacement transducer means for sensing an actual diameter of the anvil roll or a related measurement; control means responsive to the encoder means and the transducer means for generating a drive signal for driving the anvil roll at a second desired rotational speed which is a function of the actual rotational speed of the die roll and the actual diameter of the anvil roll; drive means responsive to the drive signal from the control means for driving the anvil roll at the second desired rotational speed, whereby both the die roll and the anvil roll have substantially equal circumferential surface velocities, second encoder means for sensing the rotational position of the anvil roll and feeding back a signal representative of the rotational position of the anvil roll to the control means for modulating the drive signal from the control means to synchronise the rotational position of the anvil roll with the rotational position of the die roll, tachometer means for sensing an actual rotational speed of the anvil roll and feeding back a signal representative of the actual rotational speed of the anvil roll to the control means for maintaining the actual rotational speed of the anvil roll substantially equal to the second desired rotational speed; and means for manually adjusting the ratio of the second rotational speed to the first rotational speed.

10. Apparatus according to any one of claims 1, 2, 3 or 9 and substantially as described with reference to the accompanying drawings.

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