EP0155665B1

EP0155665B1 - Vacuum die cutting apparatus for foam backed materials

Info

Publication number: EP0155665B1
Application number: EP19850103113
Authority: EP
Inventors: Martin M. Levene; William W. Lessard
Original assignee: Ontario Die Co Ltd
Current assignee: Ontario Die Co Ltd
Priority date: 1984-03-19
Filing date: 1985-03-18
Publication date: 1990-07-25
Also published as: DE3578791D1; EP0155665A2; CA1232533A; EP0155665A3

Description

The present invention refers to an apparatus for cutting a fixed pattern in each of a plurality of stacked compressible material layers comprising: a steel rule with a steel rule die defining a cutting edge means, supporting means for said compressible material layers, air-impervious cover means at least partly covering the stack of material layers, means operative to evacuate air from beneath said cover means to vertically compress said material layers to substantially reduce their vertical thickness and press said compressed, reduced thickness material layers downwardly, and means operative to move said cutting edge through said compressed reduced thickness material layers to cut a pattern in the material layers.
Steel rule dies are commonly used for cutting cloth and clothlike materials such as natural textiles, and synthetic materials such as vinyl. Steel rule dies are particularly advantageous in the repetitive cutting of specific shapes such as apparel, automobile upholstery and trim panels, and the like. In brief, a steel rule die typically comprises a base or backing board in which a slot or groove matching the pattern to be cut is sawn, and a length of steel rule embedded in the board with the sharpened exposed upper edge extending therefrom. The die is used in combination with a cutting pad and a press which may either be single-cut, progressive, or increment feed.
A problem arises when it is necessary or desirable to cut relatively thick but compressible materials such as foam-backed materials, foam rubber, waddings, battings, paddings, high pile materials, and other fluffy or spongy materials. A stack or a particularly thick single layer of such materials is sufficiently unstable that an accurate cut is often not possible using conventional techniques.
US-A-4 060 016 describes an apparatus of the above-mentioned type wherein the vertical movable cutting edge cuts from above through the air-impervious cover. Thereby the vacuum underneath the cover is destroyed before the cutting operation is completed. This results in a loss of vertical pressure on the material layers during the cutting operation.
US-A-2 217 060 shows a steel rule fixedly upstanding from a base member and having an exposed upwardly facing sharpened upper cutting edge. The material layer to be cut may be positioned thereon. This document does not mention cutting of a stack of material layers nor the use of vacuum to compress the material layers.
It is an object of the present invention to improve an apparatus of the above-mentioned kind in such a way that the vacuum underneath the air-impervious cover is not destroyed and the pressure acting on the material layers is maintained during the cutting operation.
According to the present invention this object is solved in that the steel rule die includes a base member and the steel rule is fixedly upstanding from said base member and has an exposed upwardly facing sharpened upper edge which forms said cutting edge and is adapted to have a stack of material layers positioned thereon, said air-impervious cover means covering said steel rule die and the material layers to define a vacuum chamber which is to be evacuated to compress the material layers against the cutting edge before cutting the layers.
In the inventive apparatus the steel rule is included in the vacuum chamber so that the cutting edge cannot cut into the cover. Therefore the vacuum and the pressure acting on the material layers are maintained during the cutting operation.
It is to be understood that the die of the subject invention is used in combination with a press of either the single stroke or progressive or incremental feed type. In the typical arrangement the base containing the steel rule is placed on a horizontal support surface with the sharpened upper edge of the rule facing upwardly, the materials are stacked on top of the rule and the press is oriented over the die so as to push the stack of materials against the sharpened upper edge of the rule to perform the cutting action.
A preferred embodiment of the invention further includes a layer of air permeable resilient foam material located on that base around and adjacent to the rule for supporting that compressible layers at least substantially on said sharpened top edge. This compressible foam material substantially levels with the upper cutting edge of the rule. It is open celled to act as a conduit to facilitate evacuation of the vacuum chamber underneath the cover, and compresses in response to the downward movement of the cutting press to allow the cutting edge of the rule to move through the layers of the stacked material.
In a preferred embodiment of the invention that apparatus includes a pad under the air-impervious cover means so that the sharpened edge cannot cut the air-impervious cover means. Further, this pad precludes horizontal compression of the stacked material during the cutting operation and thereby significantly improves the accuracy of the cut and the resulting dimensional uniformity of the cut pieces.
Where the steel rule forms a closed figure and the vacuum source is external of the die it is sometimes necessary to vent the interior of the closed figure defined by the steel rule to the external area of the die. In the preferred embodiment of the invention the steel rule has one or more apertures formed therein for air communication between one side of the steel rule and the other side of the steel rule.
Further preferred embodiments of the inventive apparatus are described in subclaims 4, 5 and 8.
The invention further refers to the method of cutting a stack of compressible material layers comprising: placing the compressible material layers to be cut by a cutting edge in a sealed collapsible chamber, evacuating air from the chamber to collapse the chamber and compress the compressible material and moving that cutting edge through the compressed material to cut a pattern in the material, this method being characterized by placing the upwardly facing cutting edge within the collapsible chamber and positioning the material layers on the cutting edge.
The following description describes in more detail the invention with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 is an exploded, perspective view of a steel rule die cutting arrangement according to the invention;
Figure 2 is a section through part of the apparatus of Figure 1 showing details thereof;
Figure 3 is a side view of a stack of materials on a die before compression;
Figure 4 is a side view of the same stack of materials after compression;
Figure 5 is a side view of a stack on a die using a belt-type cutting pad;
Figure 6 is an exploded view of a modified steel rule die cutting arrangement according to the invention;
Figure 7 is a cross sectional view taken on line 7-7 of Figure 6;
Figure 8 is an exploded perspective view of a further modified steel rule die cutting arrangement according to the invention;
Figure 9 is a cross sectional view taken on line 9-9 of Figure 8; and
Figure 10 is a cross sectional view taken on line 10-10 of Figure 8.

Detailed description of the specific embodiment

Referring to the drawings, the invention embodied in the apparatus of Figures 1-5 comprises a base 10 of thick plywood board having a wide rectangular groove 12 formed in the upper surface thereof and communicating with a cylindrical channel 14 which extends to the outer edge of the base board 10. The upper surface also has sawn therein an inner slot 16 defining major co-planar surfaces 18 and 20.
A strip of steel rule 22 is formed into a shape congruent with the slot 16 and in the present invention is specially formed to exhibit slots 24 in the bottom or blunt edge thereof for purposes to be described. The steel rule 22 is sharp and, in some cases, serrated along the upper exposed edge and is driven into the slot 16 of the plywood base 10. In the present instance rule 22 forms a closed figure. Accordingly, the slots 24 are formed in the bottom or blunt end of the rule with a height exceeding the extent to which the rule is driven into the board 10 so as to provide air communication passages between the interior of the figure formed by the rule 22 and the volume represented by the slot 12 in board 10.
When rule 22 is in place in the board 10 a perforated plate 26 having a substantially quadrangular configuration is placed over the slot 12 and, as best shown in Figure 2, extends substantially up to the exterior lateral surface of the rule 22.
In the illustrated embodiment a collar 28 of air tight material such as closed cell plastic or rubber is placed on the surface 20 of the board 10 and is filled in the volume between the collar 28 and the rule 22 with open cell foam 30. Similarly the interior of the figure formed by the rule 22 is filled with open cell foam 32 which rests on surface 18. The foam elements 30 and 32 essentially provide a compressible support surface for a stack 34 of compressible materials to be cut using the die shown in the drawing such that the materials do not have to rest directly on the exposed edge of the rule 22. The stack of 34 is then topped with a board 38 and, finally, covered by a thin, flexible, but airtight, plastic shroud 36 defining an air-impervious cover or shroud which is preferably substantially larger than the die apparatus so as to be capable of extending beyond the lateral boundaries thereof and onto a flat support surface such as one might find in atypical workshop where flatbed die cutting operations are carried on. Board 38 must be substantially rigid but must have a surface that is soft enough to allow at least slight penetration by rule 22. Board 38 may, for example, comprise a sheet of polypropylene, nylon, vinyl, urethane, or vinyl coated woven fabric material. Board 38 lies between the cutting edge of rule 22 and the sheet 36 to prevent cutting of the sheet and loss of vacuum during the press-cutting operation. Board 38 in effect becomes a part of the cover sheet and maintains the vacuum condition even in the event that the cover sheet is damaged. Board 38 also functions during the cutting operation to preclude horizontal compression of the stacked materials.
In operation, the assembled die comprising elements 10, 22, 26, 28, 30 and 32 is placed on a flatbed die cutting table and the stack 34 of compressible materials is placed in position over the sharp cutting edge of the rule 22. Board 38 is placed over the stack 34. Cover sheet 36 is placed over the assembly and pulled down tight against the surface of the table and a vacuum source is attached to fitting 42 which is placed in the channel 14 shown in Figure 1. The original uncompressed condition is represented in Figure 3 wherein the stack 34 may be on the order of five or six inches in vertical thickness. The "cutting-ready" condition is represented in Figure 4 where sufficient air has been drawn out from under the cover sheet 36 to vertically reduce the height of the stack 34 down to about 1" or 1 1/2" without any lateral or horizontal distortion. At this time the upper press platen 40 is operated to drive the stack 34 down over the blade or rule 22 compressing the plastic foam support materials 30 and 32 until all the layers of material in the stack 34 are cut. Board 38 serves not only as a surface that the steel rule cuts against but also serves as a seal so that air, which has been drawn out from under cover sheet 36, cannot re-enter the enclosed environment with a resultant loss of vacuum and loss of compression of the stacked materials.
Figure 5 shows an alternative embodiment where the steel rule 22 cuts against a belt-type pad 38a which is made of woven synthetic material coated/impregnated with urethane or the like to form a tough, somewhat flexible pad. In this case, the pad 38a is outside of the shroud sheet 36 such that the sheet is cut by the rule 22 with each operation of press 40. However, this inconvenience is offset by the fact that handling of pad 38a is made easier by attachment to the press 40 and by advancement thereof between supply and take-up devices 44 and 46, respectively.
In the modified steel rule die construction shown in Figures 6 and 7, identical reference numerals have been used to identify elements in the structure of Figures 6 and 7 that substantially correspond to elements in the Figures 1-5 embodiment. Thus an elongated rectangular plywood board 10 is formed with a wide rectangular groove 12, a steel rule 22 is driven into board 10 within groove 12, an open cell foam member 32 fills the interior of steel rule 22, and an open cell foam member 30 extends around the exterior of steel rule 22 within groove 12. Groove 12 in this embodiment includes portions 12a extending transversely and longitudinally beneath the steel rule to form a grid network within the exterior groove 12. In operation, the stack 34 of compressible material is placed in position over the sharp cutting edge of the rule 22, a board 38 is placed over the stack 34, a cover sheet 36 is placed over the assembly and pulled down tight against the edges of board 10 to form a vacuum chamber, and air is evacuated from the vacuum chamber through a suitable conduit 48 secured to an end edge of board 10 and communicating with groove 12. After the air has been drawn out of the vacuum chamber to compress and reduce the thickness of the stacked layers of material, the upper press platen (not shown) is operated to drive the stack 34 down over the rule 22, compressing the foam plastic support materials 30 and 32 until all of the layers of material in the stack 34 are cut. Note that this embodiment dispenses with the collar 28 and perforated plate 26 of the Figures 1-5 embodiment.
In the Figures 8 and 9 embodiment, the die assembly includes a die carrier forming a part of the feed system of the press in which the cutting operation is performed. The steel rule die in this embodiment includes a plywood board 10, a steel rule 22 mounted in board 10, an open cell foam member 32 filling the interior of rule 22, and an open cell foam member 30 positioned around the exterior of steel rule 22. The die carrier, seen generally at 50, includes a base plate 52 and a fence member 54 upstanding from and extending around the peripheral edge of base plate 52. Base plate 52 is in the form of an elongated rectangle with long side edges 52a, 52b and short end edges 52c, 52d. Fence member 54 comprises metal tubing of rectangular cross section extending in a closed loop around all four edges of base plate 52. Tubing 54 includes an imperforate bottom wall 54a, an imperforate outer wall 54b, a perforate top wall 54c, and a perforate inner wall 54d forms a vacuum channel. Tubular fence 54 extends upwardly above the surface of plate 52 by a distance generally corresponding to the composite height of the steel rule die, and the interior area bounded by fence 54 generally corresponds in size and configuration to board 10 of the steel rule die.
In operation, the steel rule die is positioned on plate 52 within tubing 54, 56 with the outer edge surfaces of open cell foam member 30 intimately juxtaposed to the respective perforate inner walls 54d of tubing 54. Stack 34 of compressible materials is placed in position over the sharp cutting edge of rule 22, board 38 is placed over stack 34, cover sheet 36 is placed over the assembly and pulled down tight against the periphery of the die carrier to form a vacuum chamber, and air is evacuated from the vacuum chamber through a suitable tubular fitting 58 received in an opening in the outer wall 54b of tubular fence 54 along the end edge 52d of base plate 52. As in the previous embodiments, as the air is sucked out of the vacuum chamber beneath the cover, the height of stack 34 is significantly compressed and reduced whereafter the upper press platen (not shown) is operated to drive the stack 34 down over the blade or rule 22, compressing the plastic foam support materials 30 and 32 until all the layers of material in the stack have been cut. Board 38 functions during the evacuation and compression step to ensure that no significant horizontal compression takes place in the stack so that the finished cut parts are acurate and uniform when they return to their normal uncompressed state after being cut. The arrangement of Figures 8 and 9 obviates the need for a separate vacuum system in each steel rule die since the vacuum system is provided on the die carrier and the same die carrier may be used with a multitude of different steel rule dies.
Figure 10 discloses a check valve to be used with any of the disclosed steel rule die cutting arrangements. For example, although the check valve is disclosed in conjunction with conduit 58 of the Figures 8 and 9 embodiment, the check valve could also be used with the fitting 48 of Figures 6 and 7 embodiment or with the conduit 42 of the Figures 1-5 embodiment. The check valve may take various forms. As disclosed, the check valve includes a lightweight hollow ball 60 coacting with a seat 64 formed in a portion 66 in an enlarged portion 58a of conduit 58. The free end of conduit 58 is adapted to receive a vacuum hose 68 which in turn is adapted to be connected to a suitable vacuum pump (not shown). In operation, the vacuum pump is operated to suck air out of the vacuum chamber beneath the cover with the ball 60 lifting off of seat 64 to allow the escape of air from the vacuum chamber. Once the vacuum has been achieved, the drive assembly is moved in the direction of the arrow in Figure 8 into a press (not shown) which makes a series of successive hits or cuts on the stacked sheets as the die assembly is fed progressively into and through the press. As the end 52d of the die carrier approaches the press, the vacuum hose 68 is removed from conduit 58 as the vacuum hose is removed, ball 60 seats against seat 64 under the urging of the differential pressure acting on the ball to maintain the established vacuum condition in the vacuum chamber as the die assembly continues its movement through the press. This arrangement avoids the necessity of having the vacuum hose move through the press and thereby greatly simplifies the overall cutting operation.
It is to be understood that various modifications and additions to the structures shown are possible; for example, where the figure defined by the rule 22 is not closed, it is possible to eliminate the slots 24 which provide air communication between the inside and outside of the figure. Another convenience is the use of a spring-biased reel for the vacuum supply fitting 42 so that vacuum hose may be paid out and re-reeled as the die is moved along a press pad. For a definition of the invention reference should be had to the appended claims.

Claims

1. An apparatus for cutting a fixed pattern in each of a plurality of stacked compressible material layers (34) comprising:

a steel rule with a steel rule die defining a cutting edge means (22);

supporting means (30) for said compressible material layers (34);

air-impervious cover means (36) at least partly covering the stack of material layers;

means (14, 42, 12) operative to evacuate air from beneath said cover means to vertically compress said material layers to substantially reduce their vertical thickness and press said compressed, reduced thickness material layers (34) downwardly; and

means (40) operative to move said cutting edge through said compressed reduced thickness material layers (34) to cut a pattern in the material layers (34); characterized in that:

the steel rule die includes a base member (10) and the steel rule (22) is fixedly upstanding from said base member (10) and has an exposed upwardly facing sharpened upper edge which forms said cutting edge and is adapted to have a stack of material layers (34) positioned thereon, said air-impervious cover means (36) covering said steel rule die and the material layers (34) to define a vacuum chamber which is to be evacuated to compress the material layers (34) against the cutting edge before cutting the layers (34).

2. Apparatus as defined in claim 1 and further including a layer of air permeable resilient foam material (30) located on said base around and adjacent to the rule (22) for supporting said compressible layers (34) at least substantially on said sharpened top edge.

3. Apparatus as defined in claims 1 or 2 wherein said apparatus further includes a pad (38) under the air impervious cover means (36) so that the sharpened edge cannot cut the air impervious cover means.

4. Apparatus as defined in one of claims 1 to 3 wherein:

said apparatus further includes a die carrier (50) defining a support surface for removably receiving the base (10) of said steel rule die;

said apparatus defines a closed loop upwardly facing sealing surface surrounding said steel rule; and

the lower peripheral edges of said air impervious cover means (36) are sealingly engaged with said sealing surface to define said sealed chamber.

5. An apparatus according to claim 4 wherein:

said apparatus further includes a closed loop tubular member (54) positioned within said chamber with said cover means sealingly engaging said sealing surface and including perforations communicating the hollow interior of the tubular member with said chamber; and

said evacuating means comprises means (58) for withdrawing air from the hollow interior of said tubular member.

6. An apparatus according to one of claims 1 and 5 wherein said steel rule (22) defines a closed figure and has one or more apertures (24) formed therein for air communication between one side of the steel rule (22) and the other side of the steel rule.

7. A method of cutting a stack of compressible material layers (34) comprising:

placing the compressible material layers (34) to be cut by a cutting edge in a sealed, collapsible chamber;

evacuating air from said chamber to collapse the chamber and compress the compressible material (34); and

moving said cutting edge (22) through the compressed material (34) to cut a pattern in the material; characterized by:

placing the upwardly facing cutting edge within the collapsible chamber; and

positioning the material layers (34) on the cutting edge (22).

8. Apparatus as defined in claim 4 wherein: said sealing surface is defined on said die carrier.