Vacuum Die Cutting Method and Apparatus

This invention relates to steel rule die cutting and particularly to a method and apparatus for cutting single and stacked layers of compressible steel rule die.

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 shirt collars, automobile interior panels and the like. In brief, a steel rule die typically comprises a base or backing board in which a groove matching the pattern to be cut is formed, and a length of steel rule embedded in the board with a sharpened exposed edge extending upwardly therefrom. The die is used in combination with a cutting table and a press which may either be single-cut or progressive feed.

A problem arises when it is necessary or desirable to cut relatively thick but compressible materials such as foam-backed vinyl, foam rubber, and plastic foam. A stack or a particularly thick single layer of such material is sufficiently unstable that an accurate cut is often not possible using conventional techniques.

One approach to the more accurate cutting of foam 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 these 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 describe 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.

It has been proposed to use steel rule blanking or cutting dies with air evacuation compression so as to facilitate and improve the use of such dies to cut compressible materials. These proposals have involved the use of an air impervious cover or shroud positioned over a stack of compressible material positioned on the steel rule upper edge to define a vacuum chamber, and means for evacuating the vacuum chamber to compress and reduce the thickness of a stack of layers before cutting the layers with the rule. Such an arrangement is shown in U.S. Pat. No. 4,543,862 assigned to the assignee of the present application. Whereas the method and apparatus disclosed in U.S. Pat. No. 4,543,862 is generally satisfactory for the cutting of compressible materials and has achieved significant commercial acceptance, the procedure of this patented process, whereby a large shroud of air impervious material is positioned over the stack of compressible material to form the vacuum chamber, is labor intensive and therefore contributes significantly to the overall cost of the process. Further, the shroud tends to wear with repeated usage and must eventually be replaced with the result that the materials cost of the process is thereby increased.

This invention is directed toward the provision of an improved steel rule die assembly utilizing air evacuation techniques.

More specifically, the present invention is directed to the provision of a steel rule die employing air evacuation techniques in which the labor and material costs of the process are minimized.

More specifically, the present invention is directed to the provision of a steel rule die, air evacuation process of the type disclosed in U.S. Pat. No. 4,543,862 in which the shroud of the patented process is eliminated with consequent labor and material savings.

According to the invention method, a generally planar support structure is provided; an upwardly facing cutting edge is provided on the support structure; a layer of compressible material is positioned over the cutting edge; an enclosure is formed over the layer of material and over the cutting edge with the enclosure including a top wall overlying the layer of material and collapsible side walls extending between the top wall and the support structure in circumferentially surrounding relation to the cutting edge and to the layer of material to define a sealed vertically collapsible chamber totally enclosing the cutting edge and the layer of material; air is evacuated from the sealed chamber to vertically collapse the side walls of the enclosure to an extent to vertically compress the layer of material and substantially reduce its vertical thickness and to press the compressed reduced thickness layer of material downwardly against the cutting edge; and the cutting edge is moved through the compressed reduced thickness layer of material by a cutting press to cut a fixed pattern in the material corresponding to the shape of the cutting edge. This arrangement retains all of the inherent advantages of the process of Pat. No. 4,453,862 while eliminating the shroud of that process and thereby eliminating the labor and material expenses associated with the shroud.

According to a further feature of the invention method, a closed loop peripheral upwardly facing sealing area is defined on the support structure around the cutting edge; the enclosure side walls are permanently secured to and extend downwardly from the enclosure top wall to form a unitary enclosure; and the sealed chamber is formed by positioning the unitary enclosure over the layer of material with the lower peripheral edges of the enclosure side wall sealingly engaging the closed loop sealing surface on the support structure. This arrangement allows the unitary enclosure to be readily positioned over the stacked layers of material by a single operator and allows the unitary enclosure to be used for repeated cutting operations without derogation of the enclosure.

In one embodiment of the invention method, the side walls of the enclosure are formed of a coated open cell material which collapses in response to evacuation of air from the chamber. This open cell construction provides an efficient and inexpensive means of providing the invention enclosure.

According to a further feature of this embodiment of the invention method, the outer surfaces of the side walls of the enclosure are coated with an air impervious material. This arrangement precludes inward movement of air through the side walls and into the vacuum chamber so as to maximize the effectiveness of the evacuation process.

In another embodiment of the invention method, the enclosure side walls comprise a curtain of flexible sheet material which collapses in response to evacuation of air from the chamber. This arrangement provides a further efficient and inexpensive means of providing the invention enclosure.

According to a further feature of this embodiment of the invention method, an annular rigid frame is secured to the lower edge of the curtain and sealingly engages with the closed loop sealing surface defined on the support structure around the cutting edge. The rigid frame coacts with the top wall to provide definition for the enclosure and provides a means of sealingly engaging the upwardly facing closed loop sealing surface on the support structure. The frame preferably has an angled cross-sectional configuration so that the frame may snuggle around the support structure defining the closed loop sealing surface.

According to a further feature of this embodiment of the invention method, a layer of resilient material is secured to the underface of the rigid frame. This arrangement facilitates the sealing engagement of the frame with the closed loop sealing surface to ensure the integrity of the vacuum chamber.

The invention apparatus comprises a generally planar support structure; a cutting edge extending upwardly from the support structure and adapted to have the compressible material positioned thereon; enclosure means including a top wall overlying the compressible material to be cut and compressible side walls extending between the top wall and the support structure in circumferentially surrounding relation to the cutting edge and to the overlying material to be cut and coacting with the support structure and the top wall to form a sealed, vertically collapsible chamber totally enclosing the cutting edge and the material to be cut; and means for evacuating air from the chamber to collapse the side walls and collapse the chamber to an extent to vertically compress the material and press the compressed material downwardly against the cutting edge. This arrangement provides an efficient and extremely cost effective apparatus for cutting the layers of compressible material on a suitable cutting press.

According to a further feature of the invention apparatus, the support structure defines a closed loop upwardly facing sealing surface in circumferentially surrounding relation to the cutting edge and the side walls of the enclosure means are secured to and extend downwardly from the top wall of the enclosure means for releasable sealing engagement at their lower peripheral edges with the closed loop sealing surface to define the sealed chamber.

According to a further feature of the invention apparatus, the apparatus further includes a PG,11 closed loop tubular member positioned within the chamber with the lower peripheral edges of the side walls of the enclosure means sealingly engaging the closed loop sealing surface; the walls of the tubular member within the chamber are perforated; and the evacuating means comprises means for drawing air out of the tubular member and thereby out of the chamber.

In one embodiment of the invention apparatus, the tubular member is positioned on the support surface in surrounding relation to the cutting edge and the closed loop upwardly facing sealing surface is defined on the upper face of the closed loop tubular member.

In another embodiment of the invention apparatus, the tubular member is positioned beneath and around the periphery of the top wall within the curtain.

According to a feature of one embodiment of the invention apparatus, the side walls of the enclosure means are formed of an open cell material which collapses in response to evacuation of air from the chamber. According to a further feature of this embodiment, the outer surfaces of the open cell side walls are coated with -an air impervious material to preclude movement of air through the side walls into the chamber.

According to a feature of another embodiment of the invention apparatus, the enclosure side walls comprise a curtain of flexible sheet material which collapses in response to evacuation of the chamber.

According to a further feature of this embodiment of the invention apparatus, a rigid closed loop frame, preferably having an angled cross-sectional configuration, is secured to the lower edge of the curtain and sealingly engages with the closed loop sealing surface.

According to a further feature of this embodiment of the invention apparatus, a layer of resilient material is secured the underface of the rigid frame to facilitate the sealing engagement of the frame with the closed, loop sealing surface.

FIG. 1 is an exploded perspective view of a steel rule die cutting apparatus according to the invention;

FIG. 2 is a longitudinal cross-sectional view of the invention steel rule die cutting apparatus showing the condition of the material to be cut before compression;

FIG. 3 is a longitudinal cross-sectional view showing the materials after compression;

FIG. 4 is a detailed view within the circle of FIG. 2;

FIG. 5 is a longitudinal cross-sectional view showing a modified form of the invention die cutting apparatus;

FIG. 6 is a plan view of a steel rule die employed in the apparatus of FIG. 5;

FIG. 7 is an exploded perspective view of a further modified form of the invention die cutting apparatus;

FIG. 8 is a longitudinal cross-sectional view of the die cutting apparatus of FIG. 7 showing the material in its condition prior to compression;

FIGS. 9 and 10 are detailed views taken respectively within the circles 9 and 10 of FIG. 8;

FIG. 11 is an exploded perspective view of a still further modified form of the invention die cutting apparatus;

FIG. 12 is a longitudinal cross sectional view of the die cutting apparatus of FIG. 11 showing the material in its condition prior to compression; and

FIG. 13 is a detailed view within the circle 13 of FIG. 12.

Referring to the drawings, the invention apparatus, broadly considered, includes a support structure or carrier 10, a steel rule die assembly 12, and an enclosure 14.

Support structure 10 includes a base plate 16 of elongated generally rectangular configuration and a tubular fence 18.

Base plate 16 is laminar and may be formed, for example, of a lower 3/8inch thick polypropylene Plate 16a suitably bonded to an upper 1/8inch thick steel plate 16b.

Tubular fence 18 is of generally rectangular configuration and extends around the perimeter of base plate 16. Tubular fence 18 is preferably formed of a metallic material and is generally rectangular in transverse cross section. The lower and outer peripheral walls 18b and 18c of tubular fence 18 are imperforate and the upper and inner walls 18a and 18d are provided with perforations 18e. A tubular spout 20 communicates with an opening 18f in the outer wall 18c of the tubular fence so as to provide communication between the interior of the spout and the interior of the tubular member.

Steel rule die assembly 12 includes a die board 22, a steel rule 24 and foam members 26.

Die board 22 may be formed of 5/8 inch thick beechwood, birch, maple, or suitable plywood and has a generally rectangular configuration sized to fit loosely within the inner perimeter of tubular fence 18.

Steel rule 24 extends upwardly from die board 22 and has an overall configuration corresponding to the desired shape to which the compressible material is to be cut. Steel rule 24 is driven at its lower edge portions into slots 22a provided in die board 22 and presents a sharpened upper exposed edge 24a.

Foam members 26 have an open cell construction and are configured to fill the areas defined between the various sections of the steel rule die 24 as well as the areas between the outer peripheral surfaces of the steel rule die and the peripheral edges of die board 22. Foam members 26 are of a thickness generally corresponding to the height to which the steel rule die portions 24 extend above the upper surface of die board 22 so that the upper surfaces of foam members 26 are substantially flush with the cutting edges of the steel rule die sections.

Enclosure 14 includes a top wall member 28 and side wall members 30.

Top wall member 28 is formed of a suitable rigid plastic material which is penetrable by the steel rule die 24. Top wall member 28 has a rectangular configuration generally conforming to the configuration of base plate 16.

Side wall members 30 are formed of a soft open cell material and are coated on their outside surfaces 30a and on their lower peripheral edges 30b with an air impervious flexible coating 32 such, for example, as a suitable urethane coating. The upper peripheral edge portions of side wall members 30 are suitably secured, as by gluing, to the peripheral undersurfaces of top wall 30 and extend downwardly from top wall 30 to form a unitary enclosure therewith. Side wall members 30 have a height generally corresponding to the height of the stack of material layers to be cut. The lower peripheral edges 30b of side wall members 30 form a closed loop downwardly facing sealing surface 30c having a size and configuration generally conforming to an upwardly facing closed loop sealing surface 18h defined by the upper surface of upper wall portion 18a of tubular fence 18.

In operation, support structure 10 is positioned on the base or lower platen 35 of a suitable cutting press steel die assembly 12 is positioned on base plate 16 within tubular fence 18; a plurality of layers 34 of compressible foam materials or other high pile or spongy fabrics having a size and configuration generally corresponding to the size and configuration of the steel rule die assembly are positioned on top of the steel rule die assembly with the lower surface of the stack resting on the upper surface of the foam members 26 in contiguous relation to the sharpened upper edges of the steel rule die 24; enclosure 14 is positioned over the stacked material layers with the side walls 30 positioned in circumferentially surrounding relation to the material stack 34 and with sealing surface 30c sealingly engaging closed loop sealing surface 18g to define a sealed, vertically collapsible chamber 36; air is evacuated from the chamber 36 by withdrawing air outwardly through perforations 18e in tubular fence inner wall 18d, the tubular interior of tubular fence 18, and spout 20 to vertically compress the stack 34 of material and substantially reduce its vertical thickness and to press the compressed reduced thickness layer of material downwardly against the sharpened upper edge of steel rule die 24; and the upper platen 38 of the associated press is lowered in known manner to move the cutting edges of the steel rule die through the compressed reduced thickness layer of material to cut a fixed pattern in the material corresponding to the composite shape of the steel rule die. The perforations 18e in the tubular fence upper wall 18a act during the evacuation and cutting process to augment the sealing engagement of sealing surface 30c with sealing surface 18g. The height of the stack of material prior to evacuation of chamber 36 is seen in FIG. 2 and the compressed height of the stack following evacuation of chamber 36 is seen in FIG. 3. Following the cutting operation, upper platen 38 is raised, the cut material is removed, a new stack of material to be cut is positioned over the steel rule die assembly, enclosure 14 is positioned over the new stack of material, and the cutting operation is repeated.

In the modified apparatus seen in FIG. 5, the apparatus comprises a support structure in the form of a die board 40, a steel rule die 42 extending upwardly from die board 40 to define the desired cutting pattern, a plurality of open cell plastic foam members 44 positioned in the spaces between the sections of the steel rule die and around the outer peripheral surfaces of the steel rule die, and an enclosure 14 including a top wall 28 and side walls 30 provided on their outer surfaces and lower edges with an air impervious coating 32. In this embodiment, the lower peripheral edges 30c of the side wall members 30 sealingly coact with a closed loop upwardly facing sealing surface 40a defined around the upper perimeter of die board 40, and air is withdrawn from the steel chamber 36 through a vacuum passage 35a in lower platen 35 communicating with slots 40b in die board 40.

Material 34 to be cut is positioned over the steel rule die, enclosure 14 is positioned over the stacked material with the lower peripheral edge 30c of the side walls of the enclosure sealingly coacting with the closed loop upwardly facing sealing surface 40a defined on die board 40, air is withdrawn from chamber 36 by drawing air downwardly through open cell foam members 44, through slots 40b and through passages 35a to vertically compress the stack 34 and to press the compressed reduced thickness stack downwardly against steel rule 42, and upper platen 38 is lowered to perform the cutting operation. Following the cutting operation, the enclosure 14 is lifted, the cut pieces are removed, a new stack of layers to be cut is positioned over the steel rule die assembly, and the enclosure is again put in position over the layers of material preparatory to a new cutting operation.

In the modified apparatus seen in FIGS. 7-10, the enclosure 46 comprises a top wall member 28, a closed loop curtain 48, and a frame 50.

As with the previous embodiments, top wall member 28 is formed of a suitable rigid plastic material which is penetrable by the steel rule die 24 and has a rectangular configuration generally conforming to the configuration of base plate 16.

Curtain 48 is formed of a flexible impervious sheet material such as rubberized nylon. Curtain 48 is secured along its upper edge to the underface of top wall member 28 by the use of suitable mechanical fasteners or suitable adhesives and depends downwardly from top wall member 28.

Frame 50 is formed of a suitable metallic material, is substantially rigid, and has a rectangular configuration with an angular cross section. Specifically, frame 50 includes a horizontal leg portion 50a and a vertical leg portion 50b. Horizontal leg portion 50a conforms in size and shape to the upper closed loop sealing surface 18g defined on the upper surface of tubular member 18. The lower edge of curtain 48 is secured to frame 50 by suitably fastening the lower edge portion 48a of the curtain to the upper face of horizontal frame portion 50a and a layer 52 of resilient material is secured to the underface of horizontal frame portion 50a. Layer 52 may, for example, comprise a suitable rubberized material. Vertical leg portion 50b of frame 50 fits snuggly around tubular fence 18 with the inner face of leg portion 50b coacting with the confronting outer face of the fence outer wall 18c to preclude lateral movement of the frame relative to the fence. A cutout 50c in vertical leg 50b allows the passage of spout 20.

In the use of the embodiment of FIGS. 7-10, material 34 to be cut is positioned over the steel rule die; a disposable rectangular cutting pad 53 is positioned on top of the stacked material; enclosure 46 is positioned over the stacked material and over pad 53 with the curtain 48 surrounding the stacked material and layer 52 sealingly coacting with the closed loop upwardly facing sealing surface 18h; air is withdrawn from chamber 36 by drawing air downwardly through the stacked layers 34, through open cell foam members 26, and through tubular member 18 for discharge through spout 20 to vertically compress the stack 34 and press the compressed reduced thickness stack downwardly against steel rule 24; and the upper platen, of the press is lowered to perform the cutting operation. Following the cutting operation, enclosure 48 is lifted, pad 53 is removed, the cut pieces are removed, a new stack of layers to be cut is positioned over the steel rule die assembly, pad 53 is positioned over the new stack, and the enclosure is again put in position over the layers of material preparatory to a new cutting operation. It will be understood that cutting pad 53 is utilized beneath top member 28 to protect the top member from the cutting action of the steel rule die.

In the modified apparatus seen in FIGS. 11-13, the enclosure 54 comprises a top wall member 56, a closed loop curtain 58, and a frame 60. Top wall member 56 is formed of a suitable rigid plastic material which is penetrable by the steel rule die 24 and has a rectangular configuration generally conforming to the configuration of base plate 15.

Curtain 58 is formed of a flexible impervious sheet material such as rubberized nylon. Curtain 58 is secured along its upper edge 58a to the underface of top wall member 56 by the use of suitable mechanical fasteners or suitable adhesives and depends downwardly from top wall member 56.

Frame 60 is formed of a suitable metallic material, is substantially rigid, and has a rectangular configuration with an angular cross section. Specifically, frame 60 includes a horizontal leg portion 60a and a vertical leg portion 60b. Horizontal leg portion 60a conforms in size and shape to a closed loop sealing surface 16c defined on the upper surface of upper steel plate 16b of base plate 16 around the steel rule die assembly 12. The lower edge 58a of curtain 58 is suitably secured to the upper face of horizontal frame portion 60a and a layer of resilient material 62 is secured to the underface of horizontal frame portion 60a. Layer 62 may for example comprise a suitable rubberized material. Vertical leg portion 60b fits snuggly around the periphery of plate 16 to preclude lateral movement of frame 60 relative to plate 16.

The apparatus of FIGS. 11-13 further includes a closed loop tubular member 64 which is positioned beneath and around the periphery of top wall 56 with the curtain 58. Tubular member 64 may be secured to the underperiphery of top wall 56 by the use of adhesives or mechanical fasteners. Tubular member 64 includes perforations 64a in its inner and bottom wall portions 64b and 64c, and a tubular spout 66 communicates with an opening 64d in the outer wall of tubular member 64 to provide communication between the interior of the spout and the interior of the tubular member.

In the use of the embodiment of FIGS. 11-13, material 34 to be cut is positioned over the steel rule die; a cutting pad 68 is positioned over stacked material 34; enclosure 54 is positioned over the stacked material with the curtain 58 surrounding the stacked material and layer 62 sealingly coacting with closed loop upwardly facing sealing surface 16c; air is withdrawn from chamber 36 by drawing air outwardly through perforations 64a, through the hollow interior of tubular member 64, and through spout 66 to vertically compress the stack 34 and press the compressed reduced thickness stack downwardly against steel rule 24; and the upper platen of the press is lowered to perform the cutting operation. Following the cutting operation, enclosure 54 is lifted, the cut pieces are removed, a new stack of layers to be cut is positioned over the steel rule die assembly, and the enclosure is again put in position over the layers of material preparatory to a new cutting operation.

In all of the disclosed embodiments, the enclosure may be lifted in and out of position over the stacked layers by a single operator using conventional suction cup lift assist mechanisms and the enclosure may be used over and over again for repeated cutting operations. The invention method and apparatus thus retains all of the advantages of the method and apparatus disclosed in U.S. Pat. No. 4,543,862 but additionally significantly reduces the labor and material costs as compared to the method and apparatus of that patent.

Whereas preferred embodiments of the invention have been illustrated and described in detail, it will be apparent that various changes may be made in the disclosed embodiments without departing from the scope or spirit of the invention.