1 ROLL FORMED FLEXIBLE DIE PLATE FOR ROTARY CUTTING TOOL

2 (123869.6)

3 RELATED APPLlCATiON 4

5 [0001] This application claims priority benefit of U.S. provisional patent application

6 Na. 60/757,799 filed on January 10, 2006. 7

8 FIELD OF THE INVENTiON

9

0 o |0002] This invention relates to improvements in rotary cutting tools and more

11 particularly to improvements in flexible die plates for rotary cutting tools. 12

13 BACKGROUND OF THE INVENTION

14

15 [0003] Rotary cutting tools are useful for manufacture of carton bianks and other

16 workpieces from sheets or webs of material, In particular, rotary die cutting tools are 1 ? used in high speed cutting of a moving sheet or web of paper, paperboard, plastics IZ or composite materials, As one example, rotary die cutting machines are used for .19 the high speed mass production of paperboard carton blanks that are subsequently 20 folded into the shape of cartons or boxes such as cereai and cracker boxes, etc.

2.1 Rotary cutting tools include solid rotary dies, where the cutting surface is made part

22 of the cylinders, and flexible rotary dies, where a die plate is wrapped around a

23 cylinder. 24

1 [0004] It is important that the die plates of flexible dies be properly affixed to the

2 cylinder and aligned, both with respect to the cylinder and with respect to each other.

3 This is especially important given the speed of rotation of the die cylinders

4 associated with high volume production. Known techniques for affixing and aligning

5 the die plates include forming the die piate out of a magnetic material and inserting

6 magnets into the die cylinders so that they are magnetically attracted to one another,

7 However, such a design greatly increases the costs of the die cylinders for several

8 reasons, including the cost of the magnets, the cost of machining holes into the ' ⁾ cylinders to receive the magnets, and tY\e difficulty in assembly.

10

11 [0005] in addition, known flexible die plates are formed by a chemical etching

12 process where an acid or base is applied Xo metal to dissolve away unwanted

13 material, in practice, a chemical is applied to a flat sheet of metal to produce the

14 desired cutting elements on a flexible die piate. The flat flexible die plate is then bent

15 around a cylinder &nύ attached by one of several methods such as use of strong l<s magnet or welding. There are numerous limitations in the chemical etching process,

) 7 both in terms of limitations in the properties of the die pates made by the process

I H and difficulties in the process for assembling the die plates to the cylinders. For

19 example, tool steels {steels with large amounts of non-ferrite alloys) are more difficult

20 to chemically etch. Chemical etching works better with carbon steels, but carbon 2) steels are relatively brittle and not ideal for forming, bending and other operations.

22 Also, some geometries such as undercuts are difficult to make. Further, known

23 chemically etched die plates are relatively thin in part to make them easier to

1 assemble to cylinders. However, thicker die plates are more desirable as they can

2 be longer lasting and more resistant to position change. 3

4 |0006] With regards to the process, use of magnets requires extensive machining of

5 cylinders, thereby making such cylinders quite expensive, Further, both magnets

6 and welding die plates to the cyϋnder require extensive changeover time when

7 switching die plates, undesirably increasing downtime for printing. Known chemically H etched flexible die pistes are awkward to assemble with the cylinder. The thin ^f) flexible die plates are shipped to the customer as flat plates that are spring-like and

10 resist bending around the cylinder It would be desirable to provide an enhanced

11 flexible die plate that is long lasting and robust, which is easy to install with reduced

12 downtime, 13

U SUMMARY OF THE INVENTION

15

H> [0007] in accordance with a first aspect, a method of making a rotary cutting tool for

17 cutting a web of material comprises the steps of roll forming a first flexible die plate

IH into a cylindrical shape, mounting the cylindrically shaped die plate onto a

19 cylindricaiiy shaped fixture, &nύ machining cutting elements onto the roil formed die

20 plate. The roll formed die plate may then be removed from the fixture and attached ! to a cylinder. The first die plate can cooperate with a second die plate attached to a 22 second cylinder to cut the thin web of material. Optionally the die plate may be roll

1 formed a second time with a radius generally equal to a radius of the cylinder to

2 which the die plate is to be attached. 3

4 [0008] From the foregoing disclosure and the foiiowing more detailed description of

5 various preferred embodiments it will be apparent to those skilled in the art that the

6 present invention provides a significant advance in the technology of rotary cutting

7 tools. Particularly significant in this regard is the potential the invention affords for S providing a high quality _> low cost method of making a flexible die plate for a rotary 9 cutting too!. Additional features and advantages of various preferred embodiments

10 wiil be better understood in view of the detailed description provided below. i l

12 BREF DESCRlPTiON OF THE DRAWINGS

13

.14 10009] Fig. 1 is a perspective view of a rotary cutting tool in accordance with a

15 preferred embodiment.

.16 [0010] Figs. 2A-2c are a series of schematic views of a flexible die plate of the rotary

17 cutting tool of Fig. 1 , showing the introduction of a radius to the flexible die plate, and

.18 ending in a die plate having a radius.

1.9 [001 1] Fig. 3 is a top side view of the cylinder with the die piate removed, showing

20 the position adjustment devices.

21 [0012] Fig. 4 is an isolated perspective view of a die cylinder adapted to receive a

22 flexibie die plate in accordance with a preferred embodiment.

1 f0013] Fig, 5 Is a perspective view of a die cylinder with a flexible die piate pulled

2 away to reveal an attachment and alignment device for the die plates,

3 10014] FIg. 6 is a close up perspective view of the attachment and alignment device

4 for the die plate.

5 f0015] Fig. 7 is an exploded perspective view of the position adjustment device.

6

7 10016] it shoυid be understood that the appended drawings are not necessariiy to

8 scale, presenting a somewhat simplified representation of various preferred features ^• ;> illustrative of the basic principles of the invention. The specific design features of the 0 rotary cutting tool as disclosed here, including, for example, the specific dimensions 1 of the cutting elements of the flexible die plates, will be determined in part by the 2 particular intended application and use environment. Certain features of the 3 iilustrated embodiments have been enlarged or distorted relative to others to improve 4 visualization and clear understanding, In particular, thin features may be thickened, 5 for example, for clarity of illustration. All references to direction and position, unless 6 otherwise indicated, refer to the orientation iilustrated in the drawings. 7 8 DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[0017] !t will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many uses and design variations are possible for the rotary cutting tool disclosed here. The following detailed discussion of various alternative and preferred features and embodiments will illustrate the general principles of the invention with reference to a rotary cutting tool suitable for use in industrial applications where flat paperboard-iike materials are to be cut. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.

[0018] Referring now to the drawings. Fig. 1 shows a rotary cutting tool 10 in accordance with a preferred embodiment having an upper die cutting assembly 96 and a lower die cutting assembly 98. The upper die cutting assembly has a cylinder 14 and die plate 18 wrapped around the cylinder, and the lower die cutting assembly 98 has a cylinder 16 and a die plate 20 wrapped around the cylinder. Each of the assemblies 96, 98 are mounted on a stand 12 so that the cylinders 14, 16 come into close proximity with one another. The upper cylinder 96 is rotatable about axis 97 and the lower cylinder is rotatable about axis 99, with the axes 97 anά 99 generally parallel with one another. Each die plate's position is preferably adjustable with respect to the die cylinder at one or more mounting locations near pins 24, 25.

|0019] Each die plate has cutting blades or elements 26, 27, preferably formed as unitary extensions of the corresponding die plate. Cutting elements are understood

1 here to include broadly any machined changes to the else plate, including raises,

2 recesses and markings. The cylinders 14, 16 are in registry with one another so that

3 they rotate together. When a thin web of material (for example, paperboard used to

4 make cereal boxes) is fed between the rotating die plates 18, 20 _r the cutting

5 elements or blades 26, 27 cooperate to cut the thin web of material into carton

6 bianks. 7

8 |0020] In accordance with a highly advantageous feature, the flexible die plates

9 disclosed herein may advantageously be roll formed prior to machining cutting 10 elements and prior to installation on the corresponding cylinder. A curve may be i l introduced to the flexible die plate so that the die piate forms a generally cylindrical

12 shape, and a radius of the die plate so produced generally corresponds to the radius

13 of a cylinder which the die plate is designed to wrap around. Figs, 2A-2C show

14 schematically a flexible die piate gradually rolled Into a generally cylindrical shape

15 which is formed to fit around a cylinder 18. The generally cylindrical shape makes

16 die plates disclosed herein much easier to Install around a cylinder than known

17 chemically etched flexible dies. Holes 120 may be formed near corners of the

.18 generally rectangular die plate prior to roil forming, to be used for attaching the die

19 piate to the fixture and to the die cylinder.

20.

21. |0021] In accordance with a highly advantageous method of manufacture, the die

22 plates may be roll formed to a cylindrical shape which corresponds to the cylindrical

23 shape of a fixture. That Ss ₃ the die piate has about the same radius as the fixture,

1 and fits snugly on the fixture. Next, the curved die plate may be mounted on the

2 fixture and machined. In addition to roil forming the flexible die plates, preferably the

3 die piates are heat treated, particularly at the cutting elements, Rockwell hardness

4 of the cutting elements of at ieast 55, and most preferably about 58-80 may be

5 achieved by heat treating. Moreover, roll-forming the flexible die plate introduces

6 stress. Application of heat to the cutting elements relieves the stress prior to

7 hardening, thereby advantageously increasing the useful life of the die plates, 8

9 [0022] if the fixture and the cylinder happen to have about the same diameter, the

10 die plate may be removed from the fixture and installed on the cylinder. If not, the

11 machined, generally cylindrical flexible die plate may be roll formed a second time

12 into a generally cylindrical shape formed to fit around the cylinder used for making

13 carton blanks. The radius of the flexible die plate so formed Is approximately the

.14 same radius as that of the cylinder 18 _S anύ most preferably a radius slightly larger

15 than the radius of the cylinder 18 to allow for snug assembly. Thus, the order of

Hs manufacture can comprise first roll forming the unmachined die plate to fit on a

17 fixture cylinder, machining cutting elements onto the die plate, heat treating the

18 cutting elements, optionally roll forming the die plate a second time to create a die 1.9 plate having a radius about the same as a cylinder it will be attached to, and then

20 assembling the position adjustment devices, magnets and die piates to the cylinder.

21 After attaching each die plates to its corresponding cylinder, fine position adjustment

22 can then occur. In final assembly _. , the die plates and cylinders can cut paperboard

23 because they are positioned in close proximity to one another as shown in Fig. 1.

1 Because of the speed of installation and the speed of disassembly, ϊt is easy to

2 switch products being manufactured, Thus, this method of manufacture of flexible

3 die plates allows for greater use of low volume or limited edition production runs.

4

5 |0023] Fig. 3 shows a preferred embodiment of a cylinder 14 with the flexible die

6 plate removed, having a position adjustment device on either side, with each position

7 adjustment device comprising yoke 90 and y~slide 30, discussed in greater detail H below. Positioned between the position adjustment devices are one or more

' ⁾ magnets 60, The magnets are used to help hold the flexible die plate in place until

10 the fasteners 24, 25 are attached. Bearer surfaces 75 may be provided, extending i l radially around the axis of rotation a little beyond the cylindrical surface. The bearer

12 surfaces can engage bearer surfaces on an adjacent cylinder and thereby act as

13 protection for the cutting surfaces of the die plates, 14

15 [0024] Fig. 4 shows the die cylinder 14 of Fig. 3, having a cylindrical surface 19 with

1f> a constant radius about an axis of rotation 97, Two sides 17 extend from either end

17 of the cylindrical surface 19 (only one side is visible in the perspective view of Fig. 3}

18 generally perpendicular to the axis of rotation and to the cylindrical surface. A large

19 space comprises pocket 62 for the magnets and pockets 64 for the fine position 0 adjustment devices. VWien the pockets 62, 64 are combined, they result in a large 1 groove cutaway in the cylindrical surface of the cylinder 14. A first opening 39 and a 2 second opening 34 are positioned on each side 17 _. . and connect to the 3 corresponding pocket 64, In certain preferred embodiments the openings 39 and 34

1 may be formed as a single opening. Openings 79 in pockets 84 of the die cylinder

2 14 are sized to receive pins for securing the corresponding yokes 90 to the cylinder.

3 [0025] Fig. 5 shows a die piate 18 with the cutting surfaces removed for simplicity of

4 illustration, ieaving only the thick die corners 29 and the alignment surfaces 111.

5 Alignment surfaces 111 can be used for guidance of the die piate in a second roll

6 forming operation to change the radius of the die plate to correspond with the radϊus

7 of the cyiinder to which it will be attached as discussed above. The die plate is B partially unwrapped around a die cyiinder 14, and when installed ends of the die

9 piate meet at the dotted Sine shown in Fig . 5. Partially unwrapping the die reveals a

10 pair of position adjustment devices. Each position adjustment device preferably n comprises a yoke 90, adjustable slide 30 and various other elements as described in

12 greater detail beiow. The adjustable slides 30 are positioned in yokes 90 which are

13 in turn connected to the die plates remote from the cutting surfaces of the die plates.

14 More specificaily, as shown in the Figs., the adjustable slides 30 are positioned on

15 the underside of the die plate 18, the side opposite the side of the die plate with the

16 cutting surfaces. In the embodiment shown in the drawings, pair of fixed pins or

17 bolts 73 secure the yoke 90 to the cylinder. Aiternatively , one of the fixed pins may .18 be replaced with an adjustable siide assembiy slidabie along the X-axis, if needed. 19

20 [0028] Fig. δ is a close-up view of one of the position adjustment devices. Preferably 1 the die plates are adjustably captivated to the die cyiinder. Adjustably captivated as 2 used herein means that the motion of one part with respect to another part is partially 3 restricted. For example, the adjustable slide 30 is free to sJide back anά forth with

iO

1 respect to the die cylinder around the axis of rotation of the die cylinder (along the Y-

2 axis labeled in Fig. 6). However, the adjustable slide is captivated so that if is held in

3 a pocket in the yoke, and cannot ieave the pocket along the Z-axis. In a similar

4 manner the outer eccentric 40 is adjustably captivated to the slide 30, and the inner

5 eccentric 50 is adjustably captivated to the outer eccentric 40,

6

7 [0027] The pocket in the yoke Is preferably oversized, in the sense that the

8 adjustable slide 30 in inserted into the pocket and leaves a gap 55 for adjustment

9 along the Y-axis, and a gap along the X-axis. The top surfaces of the yoke, slide,

10 first eccentric and second eccentric, respectively, are preferably flush with the outer

11 cylindrical surface of the cylinder. That is, these surfaces may be machined down to

12 share a common radius with the die cylinder 14. An eccentric adjustment screw 38

13 extends through first opening 39 on the side wall to urge the outer eccentric 40 to

.14 rotate with respect to the adjustable slide. A wedge adjustment screw 32 extends

1.5 through second opening 34 and engages a wedge 70 to urge the adjustable slide

16 along the Y-axis. First opening 39 and second opening 34 may alternatively be

17 formed as a single opening. An adjustable clamp 80 fills up the gap along the x-axis,

18 urging the slide 30 against one wall of the pocket In the yoke. 19

20 [0028] Yoke 90 has an opening 66 sized to receive pin 24 securing the die plate 18 1 to the yoke. In a similar manner bolt 73 extends through opening 89 to secure the

22 yoke to the cylinder. In this manner the flexible die plate is secured to the cylinder. 3 Other attachment mechanisms may also be used.

I i

1

2 [0029] Fig, 7 is an exploded perspective view of the adjustable slide assembly,

3 Wedge 70 and ciamp 80 cooperate to secure the position of the adjustable slide 30.

4 The outer eccentric sits in a cavity in the adjustable slide. The eccentric

5 engagement screw (shown in Fig. δ) engages the outer eccentric 40. The outer

6 eccentric engages the adjustable slide. Similarly, the smaller eccentric 50 engages

7 the larger eccentric 40. Opening 67 in the small eccentric 50 receives screw 25, at

S an opening in the die plate. The die plate 18 is captivated between the screw 25 and

9 the slide 30 so that the die plate is adjusted by adjustment of the adjustable slide

10 assembly.

11

U [0030] It will be apparent to those skilled in the art, that is, to those who have

13 knowledge or experience in this area of technology, that many uses and design

14 variations are possible for the flexible die plates disclosed here. The following

15 detailed discussion of various alternative and preferred features and embodiments

16 will illustrate the general principles of the invention with reference to a rotary cutting

17 tool suitable for use in industrial applications where flat paper-like materials are to be

18 cut. Other embodiments suitable for other applications will be apparent to those

19 skilled in the art given the benefit of this disclosure.