FLASHBACK IN THE PROCESS OF AUTOMATED CUTTING

OF FLEXIBLE SHEET PRODUCTS

DISCLOSURE The present invention relates to apparatus described in the preamble of

Claim 1.

Such apparatus is especially adapted for use in the process of continuous sheet product cutting such as cloth, plastic and sheet metal, where the quality of the cut surfaces is very critical and the end product must be free from defects or imperfections. In the conventional art of sheet product cutting the continuous or predefined length of material is laid on a moving conveyor, advancing the material towards the cutting zone. In the prior art, the conveyor bed is constructed in a form of sectionalized honeycomb panels or thin wall vertical ribs providing support for the flexible sheets of material. In the cutting zone, the edges of the honeycomb panel or thin wall ribs become exposed to the cutting beam causing upward reflections (flashback) of the cutting beam. The reflected cutting beam carries a sufficient amount of energy to cause unwanted deformations of the cutting pattern, particularly to the bottom surface of the material. At the same time the cutting beam causes unavoidable damage to the edges of the honeycomb or vertical rib panels as they become exposed to it in the cutting area. It has been experienced, specifically in cloth cutting applications, that the edges of the honeycomb or vertical rib conveyor deformed by the cutting beam create permanent damage to the bottom layer of material resulting in an increased number of rejected products. Users of existing sheet product cutters equipped with honeycomb or vertical rib conveyors are required to replace very frequently damaged by the cutting beam the honeycomb or vertical rib conveyor panels in order to control acceptable quality of product. The cost of constant replacement of the honeycomb or vertical rib panels is relatively high, resulting in a substantial increase of overall operating costs for a sheet product cutter equipped with this type of conveyor bed.

Also, in the existing art, the honeycomb or vertical rib panel conveyor system is equipped with the cutting beam power attenuation assembly installed

underneath the conveyor bed in the cutting beam area. The purpose of this assembly is to attenuate the active power of the cutting beam and also dispose volatile and nonvolatile substances/gasses generated during the cutting process. The shape of this particular assembly creates additional reflections of the cutting beam causing additional damage to the bottom surface of the material laid on the conveyor bed as well as to the exposed mechanical elements of the conveyor panels.

It is an object of the present invention to provide an apparatus which would at least reduce and possibly eliminate cutting beam flashbacks during the process of automatic and continuous cutting of flexible sheet products. This object is attained by providing the apparatus with structural features defined in the characterizing clause of claim 1.

Further objects and features of the invention are described in dependent claims 2 through 6. The invention will now be described by way of a preferred exemplary embodiment, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a diagrammatic illustration of a prior art material conveyor system.

FIGS. 1 A and 1 B is a diagrammatic illustration of two embodiments of a prior art of honeycomb and vertical rib conveyor panel, respectively.

FIG. 1 C is a diagrammatic illustration of cutting beam energy flashback in a prior art conveyor system. FIG. 1 D is a diagrammatic illustration of cutting beam energy flashbacks in a prior art cutting beam energy power dump assembly in honeycomb panel conveyor system.

FIG. 1 E is a diagrammatic illustration of cutting beam energy flashback in prior art cutting beam energy power dump assembly in vertical rib panel conveyor system.

FIG. 2 is a diagram of the slotted trough assembly positioned in a provide section of an endless belt conveyor.

FIG. 3 is a diagram presenting upward position of slotted trough assembly.

FIG. 3A is a diagram presenting means for securing slotted trough in a provided section of endless belt conveyor. FIG. 4 is a diagram showing means for securing vertical and transversal alignment of the cutting beam in relation to the elongated opening or cutting beam slot provided in the slotted trough.

FIG. 4A is a diagram showing means for transversal alignment of the cutting beam in relation to the elongated opening or slot provided in the slotted trough assembly.

FIG. 4B is a diagram showing means for vertical alignment of the cutting beam in relation to the elongated opening provided in the slotted trough assembly.

FIG. 5 is a block diagram of the system providing means for the fully correlated, relative movement of the slotted trough, endless belt conveyor and cutting beam delivery assembly.

DETAILED DESCRIPTION

FIG 1 , FIG.1 A, FIG.1 B, FIG.1 C, FIG.1 D and FIG.1 E illustrate diagrammatically a typical prior art honeycomb 3 or vertical rib 4 panel conveyor system 2 for cutting of a layer of a flexible material 12. The cutting beam 1 after penetrating through the thickness of the material comes in contact with the edge 7 of the honeycomb 3 or vertical rib 4 of the conveyor panel 2, causing cutting beam energy flashbacks 6 in various directions. Most of the reflected energy is directed to the bottom surface of the material resulting in undesired burnout and deformation to the edges of the pattern. At the same time, the edge 7 of the honeycomb 3 or vertical rib 4 panel element 2 becomes permanently deformed by direct exposure to the high energy cutting beam 1 . The present invention relates to different types of cutting beams, for instance LASER beam, plasma or water jet or other cutting beam. In the case, where the cutting beam falls unto spaces between the walls of honeycomb 3 or vertical rib 4 structures, its full energy is reflected from the surface of the cutting beam power (dump) attenuation assembly 10, creating secondary energy flashbacks resulting in mechanical damage to the conveyor

bed and/or the bottom surface of the material, as well as causing fires within the area of the power damp assembly.

FIG.2 illustrates a preferred embodiment of the slotted attenuator or trough 10 assembly positioned in a designated section of an endless belt conveyor 1 1. It shows that the upper run of the belt conveyor 1 1 defines a supporting surface which is referred to with reference number 42a. The trough is made of a metallic material. If desired, the inside of the trough may be covered by suitable attenuation lining in the form of a coat or a ceramic layer. Different kinds of attenuation materials are available on the market. Those skilled in the art will have no difficulty in finding a suitable material for this purpose. It is, of course, possible to simply produce the trough as a plain metallic box as is the case in the embodiment shown. The endless belt conveyor 1 1 is installed in a frame monostructure the design and construction of which is well known in this art and need not be described in detail. The purpose of the endless belt conveyor is to advance a workpiece, which — in the embodiment shown — is a layer of flexible material 12, into the area of the cutting zone 13. The length 14 and the width 15 of the cutting zone 13 is predetermined by the operating range of the cutting beam 1. The slotted trough assembly 10 is secured by other mechanical means as shown in FIG. 3 to allow its longitudinal reciprocating movement in the direction X (Fig. 4) along the cutting zone 13, in the direction of travel of the workpiece 12 to be cut. The slotted trough assembly 10 is provided with an opening of the type of a transverse slot 16 having a width which is not smaller than the diameter of the cutting beam 1 . The length of the slot 16 is defined by the width 15 of the cutting zone 13. The cross-sectional shape of the slotted trough 10 is provided in such a way that the cutting beam 1 upon completion of a cutting cycle of the flexible material 12 and after entering through the slot 16 of the slotted trough 10, will bounce off the angular shaped bottom wall of the same trough 10 and will fully attenuate its energy in a profusion of reflections from the walls of the slotted trough 10. The provided cross-sectional profile of the slotted trough 10 prevents the reflected cutting beam 1 from reappearing in the cutting zone area in the nature of flashbacks to the bottom surface of the flexible material 12 and other components of the endless belt conveyor system 11 . The volatile and non-volatile substances generated during the cutting

process within the confined slotted trough assembly 10 will be removed by a disposal system which is well known in this art and is not a part of this invention.

FIG. 3 and FIG. 3A illustrates a preferred embodiment of the slotted trough assembly 10 secured by means of two vertical brackets 20. The trough itself is shown as comprising two parallel side walls 45, 46 spaced from each other in longitudinal direction X. A bottom wall 47 slopes, in the embodiment shown, in the direction from one side wall 45 to the other 46. The vertical brackets 20 are permanently attached to either end of the slotted trough assembly 10. At the same time the vertical brackets 20 provide the mechanism to attach a set of idler rollers 17, 18 and 19. Two upper idler rollers 17 and 18 create a horizontal separation in the endless belt conveyor 1 1 while the lower idler roller 19 creates a vertical separation in the endless belt conveyor 1 1. The idler rollers and the belt thus provide a transverse channel 43 for upward positioning of the slotted trough assembly 10. The set of upper idler rollers 17 and 18 and lower idler roller 19 are connected at either end to the vertical brackets 20 to form the slotted trough carriage assembly 26, capable of performing reciprocating movement in the direction X (Fig. 4) generally in line with the direction of travel of the conveyor belt 11 and within the designated area of the cutting zone 13.

FIG. 4, FIG. 4A and FIG. 4B illustrate a preferred embodiment of the slotted trough carriage assembly 26 and other mechanical means for securing the carriage assembly 26 in relation to the endless belt conveyor 11 and the vertical and transversal alignment of the cutting beam 1 in relation to the cutting beam slot 16 provided in the top surface of the slotted trough 10. Two horizontal beams 21 are provided within the frame assembly supporting the endless belt conveyor 11 to secure installation of the slotted trough carriage assembly 26. The horizontal beams 21 are installed at the same elevation and on the opposite side of the frame structure supporting the endless belt conveyor 1 1. Both horizontal beams are provided with a predefined length of vertically and horizontally aligned precision guide rail members each of which is permanently attached to the upper or lower portion of the respective beam 21. The slotted trough carriage assembly 26 is provided with a driving mechanism driven by an external driving source 37. The external driving

source 37 may be of any type of driving equipment well known in this art and need not be described in detail. The external driving source 37 will secure reciprocating motion X of the slotted trough carriage assembly 26 within the predefined length 14 of the cutting zone 13. Both vertical brackets 20 are provided with a permanently attached guide wheel system 22 disposed in a vertical and horizontal alignment to each other in order to maintain permanent contact with the precision guide rail members 21 throughout their entire operating length and at the same time to maintain vertical and horizontal positioning of the slotted trough carriage assembly 26 in relation to the endless belt conveyor 1 1. The upper portion of the brackets 20 are provided with an adjustable mechanical means to secure installation of the cutting beam delivery assembly 23 (also generally referred to as a "cutting beam generator," and external driving source 31. The adjustable mechanical means and external drive source 31 may be of any type well known in this art and do not need to be described. The cutting beam delivery assembly 23 is disposed on a transverse support or horizontal beam 28 (Fig. 4B) by means of permanently attached guide wheel assembly 27 arranged in horizontal and vertical alignment to each other in order to maintain permanent contact the precision guide rail members 28 throughout their entire operating length and at the same time maintaining vertical and horizontal position of the cutting beam delivery assembly 23 in relation to the slotted trough assembly 10. This arrangement allows for precise vertical and transversal alignment of the cutting beam 1 in relation to the cutting beam slot 16 provided in the slotted trough assembly 10. FIG. 5 illustrates a preferred embodiment of the overall control system providing means for fully correlated reciprocating movement of the slotted trough carriage assembly 26 in relation to the motion of the belt of the endless belt conveyor 11 , and fully correlated relative movement of the cutting beam 1 in the X-Y plane with the movement of the slotted trough 10 and the movement of the endless belt conveyor 11. The overall control system is composed of a digital computer 29, motion supervisor system 30 and individual motion control elements such as motors 31 , 34, 37 and motion monitoring devices such as digital or analog encoders 32, 35, 38. It will be appreciated that the numbering used in Fig. 5 is for convenience only as the

motors 31 and 37 are the equivalents of motors 31 and 37, respectively. All of the above noted components are well known in this art and do not need to be further described. The computer system 29 is connected by means of an electronic interface with the motion supervisory system 30. The motion supervisory system 30 provides multichannel connections 40A, 40B, 40C, 40D, 40E, 40F for connecting the motor 34 and digital encoder 35 of the endless belt conveyor 1 1 and motor 37 and digital encoder 38 of the slotted trough carriage assembly 26 and motor 31 and digital encoder 32 of the cutting beam delivery system 23. The algorithm defining a complete sequence of correlated motion events for the endless belt conveyor 1 1 , slotted trough carriage assembly 26 and cutting beam delivery system 23 is stored in the memory of the digital computer system 29. The memory of the digital computer system 29 has a capability to store predetermined motion profiles for each individual motion channel 40A, 40B, 40C, 40D, 40E, 40F which in this invention includes the endless belt conveyor 1 1 , slotted trough carriage assembly 26 and the cutting beam generator or delivery system 23. The memory of the computer system 29 has also capability to store all predetermined geometrical patterns to be used in the automated cutting process of the flexible material 12. Upon initiation of the cutting sequence, the digital computer 29 will send a series of digitally coded commands to the motion supervisory system 30. The motion supervisory control system 30 will respond to the computer command by activating the motor 34 through the motion channel 40C designated for the motion control of the endless belt conveyor 11 in accordance with the motion profile stored in the memory of the computer system 29 causing a continuous forward motion of the endless belt. When a layer of the flexible material 12 laid on the endless belt conveyor 1 1 enters the cutting zone 13, the motion supervisory system 30 will activate the motor 37 through the motion channel 40E designated for motion control of the slotted trough carriage assembly 26. The motor 37 will cause a reciprocating movement of the slotted trough carriage assembly 26 in accordance with the predetermined motion profile stored in the memory of the computer system 29. At the same time the motion supervisory system 30 will activate the motor 31 through the motion control channel 40B designated for the motion control of transversal movement

Y of the cutting beam delivery system 23 in accordance with the predetermined motion profile stored in the memory of the computer system 29. Each individual digital encoder 32, 35 and 38 connected respectively to the shaft of the motor 31 , 34 and 37, generates series of digitally encoded pulses 33, 36, 39 whose electronic parameters provide information about the speed, acceleration and relative position of the belt of the endless belt conveyor 1 1 , slotted trough carriage assembly 26 and the cutting beam delivery system 23. Digitally encoded pulses 33, 36, 39 are electronically interfaced with the memory of the computer system 29. The correlation of the motion profiles for each individual motion channel 40A, 40B, 40C, 40D, 40E, 40F is accomplished by means of software program routines stored in the memory of the computer system 29. Selection of a cutting pattern in the memory of the computer system 29 will automatically determine the appropriate software routines and motion profiles for controlling the movement of the belt of the endless belt conveyor 11 , slotted trough carriage assembly 26 and the cutting beam delivery system 23. Coordination of the correlated motion procedures for each individual cutting pattern, will be executed bγ additional software routines stored in the memory of the computer system 29. These additional software routines will determine and generate all required corrective measures to the motion supervisory system 30 necessary to maintain +he accuracy of the selected motion profiles. The corrective measures will be calculated and monitored by suitable software as routines based on the comparison of electronic parameters of the digitally encoded pulses 33, 36, 39 received from the encoders 32, 35 and 38 and predetermined motion profile parameters entered into the memory of the computer system 29.

The desired elimination of cutting beam flashbacks in the area of the cutting zone in the process of automated cutting of flexible sheet products is obtained through the generally full attenuation of the energy of the cutting beam in the slotted trough assembly 10. Attenuation of the energy of the cutting beam 1 in the slotted trough assembly 10 is maintained throughout the entire process of automatic cutting by maintaining vertical and transversal alignment of the cutting beam 1 in relation to the elongated opening (slot) 16 in the top surface of the slotted trough 10 as shown in the description of the preferred embodiments of this invention.

Those skilled in the art will appreciate that many modifications may be effected to the embodiment disclosed without departing from the scope of the present invention. As one of many examples only, many different linings or other treatment of the interior of the trough 10 can be effected and the shape of the trough modified. Therefore, we wish to protect by letters patent which may issue on this application all such embodiments as fairly fall within the scope of our contribution to the art.