Ejection Member For Cutting Dies

Abstract

A resilient ejection strip for a cutting die is provided. In the production of carton blanks and the like from sheet material, such as corrugated board, slots and various other openings are frequently made in the blanks. The pieces of sheet material from which the openings are made must be ejected from the cutting dies after forming, or the dies will not be operable after several blanks are produced. A resilient ejection strip is located in a cavity or recess formed by the cutting rules to eject the severed pieces of sheet material. The ejection strip is tapered in cross section so that it cannot completely fill the cavity formed by the cutting rules and cause damage because of a lack of space to expand. The new ejection strip also has a bottom surface which is rough or textured to provide a larger surface area for the purpose of adhering the ejection strip to the die board.

Description

This invention relates to ejection members or strips for cutting dies.

In a cutting die for producing a container or carton blank, by way of example, openings are frequently produced in the blank. A common type of opening is a slot or slit which extends inwardly from an edge of the carton blank and separates flaps of the blank. Provisions for ejecting the severed piece from the cutting die must be provided. Otherwise, the severed pieces will continue to stack up on the cutting die, as they are wedged into the recess or cavity formed by the cutting rules forming the opening, and the die will become inoperable after several carton blanks are formed.

Heretofore, resilient ejection members in the form of rubber strips with rectangular transverse cross sections have been employed in the cavities formed by the cutting rules which produce the openings in the carton blank. Such ejection strips have completely filled the cavity or recess formed by the cutting rules of the blank opening and project above the upper or cutting edges of the cutting rules. When the die cuts a blank from a corrugated board, for example, the ejection strip is necessarily forced toward the die plate or board to some extent, and must be able to expand outwardly. However, with the strip substantially filling the cavity of the cutting die, there is no place for the rubber to move. Consequently, the ejection strip will sometimes bend outwardly the cutting rules or break the cutting die board. In other cases, the ejection strip will deform and damage the plastic back-up roller used with the cutting die machine to support the corrugated board during cutting.

The ejection strips heretofore used have been commonly affixed to the die board by means of adhesive. Particularly with rotary cutting dies, the ejection strips have tended to be pushed along the cutting die board during rotation, causing the strips to work loose unless fully secured to the board. Staples or similar fasteners have heretofore been used as a supplement to the adhesive in an attempt to maintain the ejection strip in position. However, this increases the labor in preparing a cutting die and the fasteners also tend to work loose after a period of time.

In accordance with the invention, a resilient ejection strip is provided which is tapered from a bottom surface or base to an upper, narrower surface to provide space in the cavity formed by the cutting rules to enable the ejection strip to expand or move outwardly when the upper or outer edge is forced in during a die cutting operation. Hence, the possibilities of the cutting rules being bent outwardly, the die board being broken, or the plastic back-up roll being damaged are eliminated.

Also in accordance with the invention, the bottom surface of the ejection strip is especially designed to provide a large contact area so that the strip can be more effectively adhered to the die board. The "roughened" surface provides a substantially larger contact area for the cement or adhesive so that stronger mounting of the resilient strip can be achieved. The special surface is produced when the ejection strip is molded by employing a mold surface which is etched. The high fidelity of reproduction of the molded rubber enables the bottom surface of the strip to effectively reproduce the etched surface to provide a greater surface area than even a knurled surface alone can achieve.

It is, therefore, a principal object of the invention to provide an improved resilient ejection strip for cutting dies.

Another object of the invention is to provide a tapered resilient ejection strip which prevents damage to the cutting rules, the die board, and the back-up roll.

Yet another object of the invention is to provide an ejection strip for a cutting die which is more effectively affixed to the surface of the cutting die board.

Many other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a schematic view in perspective of a rotary die machine embodying the invention;

FIG. 2 is a somewhat enlarged view in perspective of a rotary steel rule cutting die shown in FIG. 1;

FIG. 3 is a further enlarged view in cross section showing a die board, cutting rule, and ejection strip according to the invention, taken along the line 3--3 of FIG. 2;

FIG. 4 is a view in perspective of a plurality of resilient ejection strips embodying the invention, shown after being molded and before being separated; and

FIG. 5 is a somewhat schematic view in perspective of a mold by means of which the resilient ejection strips can be made.

Referring to the drawings and particularly to FIG. 1, a rotary die machine 10 includes an upper die cylinder 12 and a lower back-up cylinder 14. A resilient plastic layer 16 is mounted on the back-up cylinder 14 and the two cylinders are rotatably mounted in a frame or stand 18. The cylinders can be adjusted by suitable means so that the distance between them can be changed, as is well known in the art. In operation, the cylinders 12 and 14 are rotated in the directions of the arrows by suitable drive means (not shown). Corrugated board or other desired sheet material is fed between the cylinders where it is engaged by a rotary cutting die 20 and shaped or formed into a blank from which cartons or other products can be produced or fabricated.

The rotary cutting die 20 basically includes a die plate or board 22 (FIG. 2) from which steel cutting rules 24 project. Other types of rules such as creasing rules or perforating rules are also commonly used but are not shown in this instance. The die board 22 is usually made of high quality plywood formed to the arcuate shape shown, but can also be made of plastic material. Layout lines for the cutting rules can be made on the surface of the die board 22 with saw cuts then made on these lines and the cutting rules 24 inserted. Each of the cutting rules 24, as shown in FIG. 3, has an elongate main strip or portion 26 and a serrated cutting edge 28 at the upper or outer edge thereof.

When the cutting rule is to be used to form a slot or elongate notch in the corrugated board blank, the cutting rule can be bent into a U-shaped configuration as indicated at 30 in FIG. 2. Such a configuration is common to produce slots for flaps or tabs of the carton blank.

The cutting rule forms a cavity or recess 32 into which the severed piece of the corrugated board forming the slot in the carton blank ordinarily would be received. Each severed piece would pile on a previously severed one until several blanks were cut, at which time the severed pieces would project to or beyond the cutting edges 28 of the cutting rule so that the die would no longer be operable.

To prevent this, a resilient ejection strip 34 embodying the invention is placed in the die cavity 32. The ejection strip 34 preferably is made of a gum rubber having high resiliency to assure proper ejection of the severed pieces which would otherwise have a tendency to wedge in the cavity 32. As shown, the ejection strip 34 has a bottom surface or base 36 which has a width substantially equal to the width of the cavity 32 between the two portions of the U-shaped cutting rule 24 and has tapered, straight sides 38 which extend from the relatively wide lower surface 36 to a narrower upper surface 40. The strips can be made in a number of widths.

The height of the ejection strip 34 preferably is such that the upper surface 40 extends slightly beyond the cutting edges 28 to assure proper ejection of the severed piece of corrugated board. With the upper surface 40 always being narrower than the lower surface 36, space always exists in the cavity 32 between the side surfaces 38 of the ejection strip and the strip portions 26 of the cutting rules. Consequently, when the ejection strip 34 is depressed as the die 20 moves into contact with a corrugated board, the ejection strip can easily flatten or be deformed into the space within the cavity 32, without causing outward pressure to bear on the cutting rules, on the die board 22, or on the layer 16 of the back-up roll 14. The die board, at the bottom of the cavity 32, is connected to the main portion of the die board only through a few bridges which extend through notches in the cutting rules 24. Hence, the portions of the die board are not as strong as would otherwise be expected.

With the taper of the ejection strip 34 being symmetrical about a center line thereto, the upper surface 40 of the strip will be centered with respect to the cutting rules when the base 36 is between the cutting rules and bridging the gap or distance therebetween. This assures that a substantially symmetrical and even ejection force will be applied to the severed piece of corrugated board to substantially prevent the possibility of the severed piece being wedged in the space between the ejection strip 34 and one of the cutting rules forming the cavity 32. However, symmetry is not always essential to the proper operation of the cutting die.

In a preferred form, the ejection strips 34 also have undulated edges or notches 42 in the upper surfaces 40 to provide additional room for deformation of the ejection strips.

As the cutting die 20 rotates, it will be appreciated that the compressive force acting upon the ejection strip 34 will tend to push the ejection strip in a circumferential direction on the die board 22. Heretofore, the adhesive used to affix the ejection strip to the die plate has not been sufficient to prevent loosening and separation of the ejection strip so that staples or similar fasteners had to be used with the ejection strip. These added to the time required to fabricate the cutting die and, further, they would occasionally loosen and possibly cause damage to the cutting die and/or the carton blank being formed.

The ejection strip 34 in accordance with the invention is provided with a roughened texture on the bottom surface 36 which greatly increases the effective bottom area and provides a larger surface for adhesive 44, applied between the bottom surface 36 and the upper surface of the die board 22. The additional adhesion thereby obtained eliminates the need for supplemental fasteners, at least in many instances.

The ejection strips 34 are preferably produced in parallel relationship, as shown in FIG. 4, with thin connecting webs 46 connecting the bases or bottom surfaces 36 of the strips. The webs 46 can be easily cut or pulled apart to separate the ejection strips 34 into individual pieces and yet a number of the ejection strips can be molded at one time as a unit. These can be made with a mold 48 of FIG. 5 which includes a base 50 and a lid 52. A plurality of mold cavities 54 are formed in the base 50 and are appropriately shaped to form the ejection strips 34. Adjacent walls 56 forming the mold cavities 54 do not extend quite to upper edges 58 of the mold cavities so that the connecting webs 46 are formed in the mold by the space between the edges 56 and the lid 52. If desired, the webs can be subsequently cut with a serrated or notched knife edge to facilitate their subsequent separation. The lid 52 consists of a metal plate 60 on the lower surface of which is a knurled configuration indicated at 62. The surface 62 is not only knurled but also is acid etched with the knurling and etching producing a much greater surface area on the bottom surfaces 36 of the strip 34 than obtainable with a smooth surface or even one that is knurled alone. The liquid gum rubber used in the mold 48 provides a sufficient fidelity of reproduction to achieve the desired knurled and etched surface on the bottom of the ejection strip.

It will thus be seen that the ejection strip according to the invention through its particular shape provides sufficient space in the cutting rule cavity to allow for deformation and transverse movement of the rubber. The ejection strip also provides a large bottom surface for increasing the effective adhesion between the ejection strip and the upper surface of the die plate.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

Claims

We claim:

1. A plurality of resilient ejection members for cutting dies for producing blanks of predetermined shapes from sheet material, said resilient ejection members comprising a plurality of elongate bodies of resilient material, each of said bodies having a tapered shape as viewed in transverse cross section, said bodies being arranged in parallel relationship with the wider surfaces thereof connected together by thin, readily partible webs forming a common surface for all of said ejection members.

2. A plurality of resilient ejection members according to claim 1 characterized by each of said members having a generally undulated edge as viewed in longitudinal cross section, the minimum height of each of said members, as viewed in longitudinal cross section, being many times the thickness of said webs.

3. A plurality of resilient ejection members according to claim 1 characterized by each of said bodies of resilient material having a truncated triangular shape as viewed in transverse cross section.

4. A plurality of resilient ejection members according to claim 1 characterized by said common surface having a rough texture.

5. In combination, a die plate, at least two cutting rule means extending from said die plate and forming a cavity therewith, and a resilient ejection member positioned in the cavity and spaced from the cutting rule means at the outer edges thereof, said ejection member having a base extending substantially completely across the cavity between said cutting rule means and having tapering side walls extending upwardly therefrom, and adhesive affixing said base to said die plate.

6. The combination according to claim 5 characterized by said tapered side walls terminating in an upper surface at least partially parallel to and narrower than the base.

7. The combination according to claim 6 wherein said upper surface is spaced from the die plate a distance greater than the cutting edges of the cutting rule means.

8. The combination according to claim 5 characterized by said resilient ejection member being of gum rubber having high resiliency.

9. An ejection member according to claim 8 characterized by the wider one of the surfaces of said member, as viewed in transverse cross section, being rough.

10. A resilient ejection member for a cutting die for producing blanks of predetermined shape from sheet material, said resilient ejection member comprising an elongate body of gum rubber having high resiliency, said body having a truncated, triangular shape as viewed in transverse cross section, and said elongate body having a generally undulated edge as viewed in longitudinal cross section.

11. In combination, a die plate, cutting rules extending from said die plate, having cutting edges located a given distance from said die plate, and forming a cavity with said die plate, and an elongate, resilient ejection member positioned in said cavity and affixed to said die plate, said ejection member having a generally undulated edge as viewed in longitudinal cross section, with portions of said undulated edge extending above the cutting edges of said cutting rules and with other portions of said undulated edge being below the cutting edges of said cutting rules.

12. The combination according to claim 11 characterized by said ejection member having a base extending substantially completely across the cavity between said cutting rules and having tapering side walls extending upwardly therefrom.

13. The combination according to claim 12 characterized by the lower surface of said base having a rough texture and being affixed to said die plate.