Vacuum die cutting apparatus for foam backed materials

A stationary steel rule cutting die for cutting a fixed pattern in each of a plurality of stacked compressible material layers according to the shape of the rule die, including a vacuum system for vertically reducing the stack height of the compressible material layers without lateral distortion prior to cutting and retaining the compress condition during the progressive or incremental cutting operations. '

BACKGROUND OF THE INVENTION 
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. 
One approach to the more accurate cutting of compressible materials is 
disclosed in U.S. Pat. Nos. 3,790,154, 3,765,289, and 3,815,221, all 
assigned to Gerber Garment Technology, Inc. of East Hartford, Conn. These 
patents, and other related patents assigned to Gerber, disclose a vacuum 
table which is used primarily to hold sheet material in place while it is 
cut by a two-axis single blade jigsaw type cutter. According to these 
patents, a sheet of Mylar or other air impervious material can be placed 
over a stack of compressible materials such that the vacuum table creates 
a vacuum under the sheet to pull downwardly on the sheet and maintain the 
entire stack in a stable, compressed condition during the cutting process 
In a further Gerber U.S. Pat. No. 4,060,016, the jigsaw type cutter is 
replaced by a rotatable turret carrying a plurality of blanking dies which 
are selectively rotated into position and driven downwardly through an air 
impervious sheet and through the stacked materials to form a stack of cut 
patterns corresponding to the shape of the particular die selected. In all 
of the patented systems the board on which the stacked material is located 
must be capable of receiving the penetrations of the reciprocating knife 
as well as maintaining a vacuum for the principal purpose of holding the 
stack in place and for the secondary purpose of evacuating the volume 
under the air impervious sheet. 
All of these patented arrangements also suffer from the disadvantage that 
the air impervious sheet is cut in the process of cutting the stacked 
material layers with consequent loss of vacuum and thereby a loss of 
stability of the stack. And whereas certain of the Gerber patents 
described means for "healing" the cut in the air impervious sheet behind 
the cutting member, these healing arrangements unduly complicate the 
overall cutting apparatus and/or are not totally successful in preventing 
loss of vacuum with a consequent loss of stability of the stack. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is directed toward the design and use of stationary 
steel rule cutting dies with air-evacuation compression techniques so as 
to facilitate and improve the use of such dies to cut compressible 
materials. 
According to a basic feature of the invention, a cutting edge and 
compressible material to be cut by the cutting edge are placed in a 
sealed, collapsible chamber; air is evacuated from the chamber to collapse 
the chamber and compress the compressible material against the cutting 
edge; and the cutting edge is moved through the compressed material to cut 
a fixed pattern in the material corresponding to the shape of the cutting 
edge. Since the cut occurs from within the sealed chamber, the integrity 
of the chamber is not destroyed in the cutting operation. 
According to a further feature of the invention, the cutting edge is 
defined by a steel rule die including a base and a steel rule upstanding 
from the base; the compressible material is placed on the sharpened upper 
edge of the steel rule; and the sealed, collapsible chamber is defined by 
an air impervious cover sheet placed over the compressible material and 
over the base of the steel rule die so that, when air is evacuated from 
beneath the sheet, the sheet is pulled downwardly to compress the material 
against the sharpened upper edge of the steel rule. 
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. 
In the preferred form, a pad or board of rigid but relatively soft material 
is placed over the stack of material to be cut so that the steel rule 
cutting edge works against and actually penetrates slightly into the baord 
and the board functions to maintain the vacuum condition even in the event 
of damage to the air impervious sheet. In accordance with the invention, 
the board can be placed either over or under the air-impervious sheet. 
Where ease of handling is the overriding consideration, the board may be 
placed over the air impervious sheet. However, in most situations it is 
preferably to place the board under the sheet since this eliminates 
periodic replacement of the sheet and, very importantly, 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 form the steel rule is formed with regular-occuring gaps 
in the unsharpened side of the rule so as to provide vents to equalize 
pressure as between the inside and outside of any closed figure formed by 
the rule. 
Compressible members are provided on the base adjacent to the rule for 
supporting the compressible material layers substantially level with the 
upper cutting edge of the rule. The compressible members are open celled 
to act as a conduit to facilitate evacuation of the vacuum chamber, and 
compress in response to downward movement of the upper platen to allow the 
cutting edge of the rule to move through the layers of stacked materials. 
In one disclosed embodiment of the invention, a groove is formed in the 
base adjacent but outside of the rule, the groove is connected to suitable 
vacuum pump means, and open celled compressible members are positioned 
between the groove and the outer perimeter of the rule. 
In another disclosed embodiment, an upstanding collar member extends around 
the outside of the groove and a rigid perforate plate covers the groove 
with an open celled compressible member positioned between the collar and 
the rule and overlying the perforate plate. 
In a further embodiment of the invention, the base of the steel rule die is 
supported on a die carrier and the die carrier includes means which are 
operative to exhaust air from a vacuum chamber formed beneath the 
air-impervious cover to compress and reduce the thickness of the stacked 
materials prior to the cutting operation. The die carrier defines a 
suitable vacuum surface and the steel rule die defines a vacuum surface 
generally conforming in size and shape to the vacuum surface on the die 
carrier so that the steel rule die may be positioned on the die carrier 
with the vacuum surface on the steel rule die intimately juxtaposed to the 
carrier vacuum surface to allow evacuation of the vacuum chamber. This 
arrangement obviates the need for a vacuum device as a part of each steel 
rule die. 
According to a further aspect of the invention, the die includes a conduit 
for communicating the vacuum chamber with a suitable vacuum pump means and 
a check valve is provided in the conduit which functions upon 
disconnection of the conduit from the vacuum pump means to maintain the 
vacuum condition in the vacuum chamber. With this arrangement, the vacuum 
hoses connecting the die with the vacuum pump may be disconnected from the 
vaccum after a vacuum has been achieved so that the vacuum hoses need not 
accompany the die in its movement through the press. This arrangement is 
particularly desirable when a die is being moved through a progressive 
press involving a plurality of progressive cutting stations.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT 
Referring to the drawings, the invention embodied in the apparatus of FIGS. 
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 FIG. 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 air-tight, 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 a typical 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 32. 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 FIG. 1. The original uncompressed condition is 
represented in FIG. 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 FIG. 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 11/2" 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 
serve 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. 
FIG. 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 FIGS. 6 and 7, 
identical reference numerals have been used to identify elements in the 
structure of FIGS. 6 and 7 that substantially correspond to elements in 
the FIGS. 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 vacumm 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 FIGS. 1-5 
embodiment. 
In the FIGS. 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 all inperforate 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 stacked 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 accurate and uniform when they return to their normal 
uncompressed state after being cut. The arrangement of FIGS. 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. 
FIG. 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 FIGS. 8 and 9 embodiment, 
the check valve could also be used with the fitting 48 of FIGS. 6 and 7 
embodiment or with the conduit 42 of the FIGS. 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 FIG. 8 into a press (not shown) 
which makes a series of successive hits or cuts on the stacked sheet 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 rereeled as the 
die is moved along a press pad. For a definition of the invention 
reference should be had to the appended claims.