US3780607A

US3780607A - Method and apparatus for cutting sheet material

Info

Publication number: US3780607A
Application number: US00214579A
Authority: US
Inventors: H Gerber
Original assignee: Gerber Garment Technology Inc
Current assignee: Gerber Technology LLC
Priority date: 1972-01-03
Filing date: 1972-01-03
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25
Also published as: JPS4874683A; DE2300432A1; DE2300432B2; FR2163126A5; GB1383944A

Abstract

A method and apparatus for cutting sheet material utilize a reciprocating cutting blade that is guided through a layup of sheet material along a cutting path defining the periphery of a pattern piece. The cutting blade is positioned generally perpendicular to the sheet material being cut and bears a cutting edge which is advanced through the sheet material as the blade is reciprocated. The stroking speed of the reciprocating cutting blade is regulated as the cutting blade advances to prevent excessive heat from being generated due to the frictional contact of the reciprocating cutting blade and the sheet material. Along sections of the cutting path which permit rapid advancement of the cutting blade, the stroking speed is increased to optimize the cutting operation without generating excessive heat and thereby fusing the sheet material. At other sections of the cutting path where the rate of advancement is decreased, the stroking speed is also decreased to reduce local heating and fusion.

Description

United States Patent [1 1 Gerber Dec. 25, 1973 METHOD AND APPARATUS FOR CUTTING SHEET MATERIAL [75] Inventor: Heinz Joseph Gerber, West Hartford, Conn.

[73] Assignee: Gerber Garment Technology, Inc.,

East Hartford, Conn.

[22] Filed: Jan. 3, 1972 [21] Appl. No.: 214,579

Primary Examiner.l. M. Meister Attorney-John C. Linderman [5 7 ABSTRACT A method and apparatus for cutting sheet material utilize a reciprocating cutting blade that is guided through a layup of sheet material along a cutting path defining the periphery of a pattern piece. The cutting blade is positioned generally perpendicular to the sheet material being cut and bears a cutting edge which is advanced through the sheet material as the blade is reciprocated. The stroking speed of the reciprocating cutting blade is regulated as the cutting blade advances to prevent excessive heat from being generated due to the frictional contact of the reciprocating cutting blade and the sheet material. Along sections of the cutting path which permit rapid advancement of the cutting blade, the stroking speed is increased to optimize the cutting operation without generating excessive heat and thereby fusing the sheet material. At other sections of the cutting path where the rate of advancement is decreased, the stroking speed is also decreased to reduce local heating and fusion.

12 Claims, 7 Drawing Figures PATENTEUU I973 .SHEEI10F3 FIG. 3

FIG. 2

PATENTEDDECZ 51015 SHEET 2 0F 3 MARKER 80 FIG. 4 I I I BASIC @UCZ COMMANDS 2 I I I DIGITIZER DATA RECORDER TAPE CONTROLLER PROCESSOR 82 l POINT BASIC CUTTING CONTROLLER e DRIVER 9 /I4O I44 I36 MOTOR X T SHAPER STROKE CIRCUIT DRIVER l 70 I42-- I \Y RATE /G i |3O 44 STROKI l MOTOR x DRIVER x MOTOR -1 -|32 I J Y DRIVER Y MOTOR I4 /-2O FIG. 6

CONTROLLER 9 DRIVER I I36 7O STROKE STROKING MOTOR x DRIVER x MOTOR r I I I I32 I 54 l Y DRIVER Y MOTOR PAIENIEDUEBESIS'YS FIG. 5

CHANGE IN DIRECTION ENTRY REDUCE SPEED I /'IO6 I STOP FEED I REDUCE SPEED 00 EXIT I I j I FEED PROPORTIONAL 98 I TO AX,AY --1I YES /II2 I EXIT mz FEED, SPEED NO PROPORTIONAL ,95

TO Ax,AY I z1 l. FEED RATES I EXIT -ll4 I 2. STROKING SPEEDS I I3. HARDWARE LIMITS I 5. AD ,AD I 1 I I I I II6 I DOES I MAX. FEED YES EXCEED HARDWARE I I LIMITS II8 I REDUCE FEED, SPEED EXIT 2O EXIT METHOD AND APPARATUS FOR CUTTlNG SHEET MATERIAL BACKGROUND OF THE INVENTION The present invention relates to method and apparatus for cutting sheet material. More particularly, the present invention relates to the method and apparatus in which a reciprocating cutting tool is driven at a regulated stroking speed as the blade is advanced or guided along a line of cut through a layup of sheet material such as that utilized for manufacturing upholstery, garments or the like.

The use of automatic control equipment for cutting large numbers of pattern pieces from sheet material, such as fabrics from which wearing apparel, upholstery and other articles are made, is already well-known in the art as indicated in US. Pat. No. 3,495,492 entitled Apparatus for Working On Sheet Material" and assigned to the assignee of the present invention. In cutting mechanisms of this type, a reciprocating cutting blade is generally stroked in a direction normal to the sheet material as the cutting edge of the blade is advanced or guided along a predefined cutting path by a digital or analog controller. The controller derives basic commands from a memory device such as a punched or magnetic tape on which a cutting program is recorded. As the tape is read, the controller interprets the basic commands and causes the cutting blade to be operated and to move along a desired line of cut defining the periphery of a pattern piece in cutting engagement with the fabric layup. Because of the speed and accuracy with which automatic cutting equipment cuts out a plurality of pattern pieces from multi-ply layups of fabric sheet material, such cutting mechanisms have received favorable acceptance in the apparel industry where large quantities of pattern pieces are desired.

When a reciprocating cutting blade plunges into a layup of fabric material and advances along a line of cut with a chopping blade stroke, that is a stroke which causes the blade to be withdrawn and plunged back into the material during each reciprocation cycle, it is necessary to insure that the reciprocation rate is sufficiently high so that the forward motion of the blade does not out run the stroking of the blade and produce what is sometimes called in the trade stitching/During stitching," the fabric material is not completely severed at each point along the line of cut because the cutting blade is advanced too rapidly during a single reciprocation of the blade and allows the material to pass under the blade as it is withdrawn without being cut. The parameters which determine the uppermost limit at which a reciprocating blade can be advanced without stitching are the width of the blade, the stroke of the blade and the reciprocation rate. The chopping blade stroke, rather than a shorter stroke which leaves the cutting blade in the material at all times, is preferred, particularly with thermoplastic vinyls and similar materials that have low fusing temperatures, because the guide or sheath within which the blade reciprocates is brought in contact with a greater portion of the cutting blade during each reciprocation cycle and permits heat generated by friction between the blade and the material to be transferred away from the blade. Accordingly, there is improved heat transfer and less opportunity for fabrics to be heated to elevated temperatures and to fuse as the cutting blade advances along the line of cut.

it will be understood that to avoid stitching" in a cutting mechanism having a fixed reciprocaton rate and stroking speed, the stroking speed of the cutting blade must be selected for the maximum speed of advancement of the cutting blade through the sheet material. The drive motor and drive train for stroking the cutting blade are, therefore, designed in accordance with the maximum speed of advancement of the cutting blade and, in the past, the blade was driven at the designed speed at all times. In selecting a fixed reciprocation rate, it is necessary to keep in mind the fact that certain materials fuse when the reciprocation of the cutting blade produces excessive heat in the fabric layup. Local hotspots along the cutting path may be generated where the blade advancement is interrupted or where the rate of advancement of the cutting blade is reduced due to limitations of the cutting mechanism. For example, when the cutting blade is guided around curves having a short radius or is advanced along a very short path segment, it is customary to reduce the feed rate of the cutting blade to maintain accurate tracking of the cutting path and to prevent undue wear on the mechanical components of the cutting mechanism. If the designed reciprocation rate of the cutting blade is high in order to make rapid traverses along straight sections of the cutting path, it is possible that at localities along the cutting path where the feed rate is reduced excessive heat will be generated in the layup due to the prolonged frictional contact between the layup and the rapidly reciprocating blade. The excessive heat can cause fusion between the different plies of the layup and also across the cut so that the pattern pieces are not entirely severed from each other and from the remnant fabric. In addition, the material itself may be damaged and thereby rendered useless for its intended end product. It will be understood that a compromised reciprocation rate providing a useful high speed traverse and avoiding fusion at low feed rates must be obtained in a system in which the cutting blade is driven at a constant stroking speed, and that the performance of the cutting mechanism in such a system may not be optimum.

In accordance with the present invention, a cutting system is disclosed in which the cutting blade is reciprocated at an adjustable stroking speed and the stroking speed is regulated as the blade advances along the path in accordance with the feed rate of the blade and the material or the geometry of the cutting path.

SUMMARY OF THE INVENTION The present invention resides in a method and apparatus for cutting a layup of sheet material along a path defining the periphery of a pattern piece. A cutting blade having a cutting edge extending along the leading edge of the blade is reciprocated in a direction generally parallel to the cutting edge and perpendicular to the sheet material in the layup by stroking means such as a variable speed motor and crank linkage. Controlled drive means for moving the reciprocating cutting blade and the layup relative to one another causes the cutting edge of the blade to move along the cutting path in cutting engagement with the material in the layup at a controlled feed rate. The drive means for moving the blade also includes means for rotating the cutting blade about an axis extending in the same direction as the cutting edge in order to maintain the blade generally aligned in the fore and aft direction with the direction of out along the path. The stroking means for reciprocating the blade is connected to stroking control means for regulating the stroking speed of the reciprocating blade as the blade is moved along the cutting path. The stroking speed is generally adjusted to increase with increasing feed rates and to decrease with descreasing feed rates. The cutting apparatus employing the control means for regulating the stroking speed is a more versatile device in that the full capacity of the apparatus is utilized. High speed traverses can be executed with a chopping blade stroke without stitching" and the blade moves at slow speed along difficult contours in the cutting path without generating excessive heat and causing fusion between the plies of the layup.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cutting apparatus embodying the present invention.

FIG. 2 is a fragmentary cross-sectional view of the cutting apparatus in FlG. l taken along a line of cut and showing the reciprocating cutting blade in cutting engagement with a fabric layup on a cutting table having a penetrable bed.

FIG. 3 is a fragmentary plan view of a layup and a typical cutting path segment which is traversed by the cutting blade.

FIG. 4 is a block diagram showing a generally complete cutting system by which the present invention is practiced.

FIG. 5 is a flow diagram of the logic contained within the data processor in FIG. 4.

FIG. 6 is a schematic diagram of one embodiment of the apparatus in the present invention.

FIG. 7 is a schematic diagram of another embodiment of the apparatus in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show generally the cutting apparatus which performs a cutting operation in a layup of sheet material in accordance with the present invention. The apparatus, generally designated 10, is comprised of a cutting table 12, a cutting tool taking the form of a reciprocating cutting blade 14, a carriage mechanism composed of an X carriage l6 and a Y carriage 18 for translating the cutting blade 14 in the X and Y directions respectively over the cutting table 12 and a controller 20 which produces cutting control signals from a cutting program on a memory tape 22. Basic commands on the tape 22 are converted by the controller 20 into the control signals. The control signals are transmitted through a control cable 24 to the X carriage l6 and are distributed to various components on the

carriages

16 and 18, including the drive motors for the blade 14, to cause the desired pattern piece to be cut from a layup L of sheet material supported on the table 12. The sheet material may be used for making wearing apparel or upholstery and the like.

The cutting table 12 contains a penetrable bed 26 defining the support surface on which the sheet material is spread in the layup L. The penetrable bed 26 may be formed from a material such as styrofoam blocks or bristled mats which permit the cutting blade 14 to reciprocate in a direction perpendicular to the support surface and the sheet material spread thereon and into the penetrable bed to completely sever the sheet material throughout the entire depth of the layup as indicated in FIG. 2. The bed 26 may also be provided with a vacuum holddown system having a plurality of channels 30 which extend through the penetrable bed to a vacuum chamber 32 within the table frame. An overlay 34 of an impervious material such as a polyethylene sheet is spread over the layup and by drawing a vacuum through the channels 30, a subatmospheric pressure is generated at the support surface of the table i2 and, in conjunction with the overlay 34, causes the layup L to be held in a compressed condition. For a more detailed description of a cutting table having such a construction, reference may be had to U.S. Pat. No. 3,495,492 entitled Apparatus For Working On Sheet Material" and having the same assignee as the present invention.

The carriage 16 is mounted on a pair of gear racks 40, 42 which extend longitudinally along the edge of the work table 12 in the indicated X direction. The carriage 16 has an X drive motor 44 which is connected in driving engagement through pinions (not shown) with each of the gear racks 4b, 42 so that the X carriage 16 can translate in the X direction back and forth over the table 18. The Y carriage i8 is mounted from the X carriage 16 by means of a guide rail 50 and lead screw 52 which extend in parallel relationship between opposite lateral ends of the X carriage 16. A Y drive motor 54 is connected in driving relationship to the lead screw 52 and the screw 52 is threadably engaged with the Y carriage R8 in order to shift the carriage 18 in the indicated Y direction relative to the X carriage 16 and the table 12. Composite motions of the X and Y carriages l6 and l8 parallel to the work surface of the bed 26 permit the cutting blade 14 to be translated to any desired location over the layup L spread on the table 12.

The cutting blade 14 is suspended from the projecting end of the Y carriage 13 by an adjustable platform 60. The platform 60 can be adjusted in a direction perpendicular to the work surface of the bed 26 so that the cutting blade 24 can be raised or lowered between an elevated position in which the cutting blade is spaced above the layup L and a lowered or work position in which the cutting blade reciprocates in cutting engagement with the layup and penetrates into the bed 26 as indicated in FIG. 2. The cutting blade 14 extends downwardly from the adjustable platform 60 in generally perpendicular relationship with the work surface and the layup L of sheet material and is held in a chuck 62 rotatable relative to the platform 60 about a vertical or 6 axis also perpendicular to the work surface. The d-rotations of the chuck 62 and the cutting blade 14 are produced by a 6drive motor 64 and a belt and pulley system 66 connecting the motor 64 to the supporting chuck 62 for the cutting blade. Rotation of the cutting blade about the 0 axis permits the cutting blade to be translated along a cutting path aligned in the fore and aft direction with the line of cut at each point along the path. All of the

drive motors

44,54 and 64 receive control signals during a cutting operation from the controller 20 to move the cutting blade M along the desired line of cut in cutting engagement with the sheet material of the layup.

A variable speed stroking motor 70 connects through a crank or eccentric drive linkage 71 similar to the linkage shown in U.S. Pat. No. 3,477,322 to the cutting blade 14 in order to reciprocate the cutting blade through the sheet material and the work surface of the bed 26 as the blade is advanced along the cutting path by

drive motors

44 and 54. Control signals for regulating the speed of the stroking motor 70 are also derived from the tape program 22 by the controller 20 as described in greater detail below. The stroke of the cutting blade produced by the motor 70 and drive linkage 71 is preferably a chopping blade stroke in which the cutting blade is lifted entirely out of the layup L during each reciprocation cycle. A presser foot 72 most clearly seen in H6. 2 and having a central aperture 74 through which the blade reciprocates is also suspended from the adjustable platform 60 and slides over the overlay 34 covering the layup L. The presser foot 72 prevents the sheet material from being lifted with the blade 14 during the up-stroke and, therefore, assists the blade during the cutting operation. The blade 14 has a sharp, knife edge extending along the leading edge 76 which is advanced in cutting engagement with the layup material along the programmed line of cut. The trailing edge 78 or heel of the blade 14 is generally not sharpened but may be if desired. The lower end of the blade 14 also contains two angled knife edges 80, 82 which permit the blade to be plunged through the sheet material to begin a cutting operation at any point on the layup L. Also, the knife edges 80, 82 assist the blade in penetrating the layup during each reciprocation cycle when a chopping blade stroke is used.

In accordance with the present invention, basic commands defining the line of cut to be followed during the cutting operation are derived from the tape 22 and translated by the controller 20 into movements of the cutting blade along the programmed line of cut while the stroking speed of the blade is regulated to optimize the cutting operation. The optimization is achieved principally by increasing the cutting speed as the feed rate increases along generally linear portions of the cutting path to prevent stitching and by reducing the stroking speed as the feed rate decreases along relatively short or irregularly shaped segments of the cutting path to prevent fusion of the material or excessive heating of the blade and the material.

A typical portion of a programmed cutting path is shown in a plan view of the layup L in FIG. 3 for the purpose of explaining the various feed rate changes that are commonly encountered in a cutting operation and the manner in which the stroking speed is adjusted in accordance with the present invention. The blade 14 is shown advancing toward point A along a generally straight segment of the cutting path P. Until the blade is very close to point A, the blade 14 can travel toward the point A at the maximum feed rate of the carriages l6 and 18 without exceeding the hardware limitations, such as acceleration rates associated with the X, Y and 0 control axes, and without causing undue wear to the mechanical drive components because the changes in the control parameters are relatively small from point to point along the cutting path. In the prior art cutting mechanisms, the maximum programmed feed rate may be limited by the compromised stroking speed which may be reduced below the maximum obtainable stroking speed to prevent excessive heating in material at low feed rates. In accordance with the present invention, the stroking motor 70 is regulated by the memory tape program to produce the maximum reciprocation rate or at least a rate commensurate with the maximum feed rate without stitching" so that the displacement of the blade per reciprocation cycle does not exceed the width of the blade between the leading and trailing edges. Preferably, the displacement per cycle is somewhat less than the width of the blade.

When the blade reciprocates at high speed and also advances along the path P at a high programmed feed rate, there is little danger that the heat generated between the reciprocating blade and the sheet material will cause local hotspots and fusion between the plies of the layup or across the line of cut.

Since the angle in the cutting path at point A is larger than a predetermined angle, for example 30, the cutting blade 14 can not move continuously around the corner without exceeding the capabilities of the equipment. It, therefore, is necessary to stop the advancement of the blade adjacent point A, lift the blade out of the sheet material and rotate the blade about the 0-axis into alignment with the next segment AB of the path P before the blade continues along the path P. A method of executing such an operation with automatic lifting is described in greater detail in a co-pending application Ser. No. 183,107, filed Sept. 23, 1971 entitled Method for Cutting Sheet Material and for Generating Related Controller Commands and having the same assignee as the present invention. If the blade were allowed to reciprocate at a high stroking speed before it is withdrawn and after it plunges back into the layup material, it is possible that fusion of the sheet material could occur in the vicinity of the point A. in accordance with the present invention the programmed stroking speed of the stroking motor is reduced to a value that does not generate excessive heat and the cornering operation is then executed without difficulty.

The programmed feed rate for the relatively short segment AB is significantly smaller than the maximum because the carriages l6 and 18 would not achieve maximum speed and, if they attempted to achieve maximum speed, there would be extensive strain and wear to the mechanical components and drive motors of the cutting system. in accordance with the present invention, the basic commands from the tape 22 prescribe a reduced feed rate and correspondingly a reduced stroking speed which is suitable for short displacements of the blade less than a predefined amount. The rate of advancement and the stroking speed may, for example, be made proportional to the length of the cutting path segment AB. When the blade reaches point B it is lifted and rotated as at point A because the change in direction of the cutting path is, again, too large to be executed by merely rotating the blade in the layup.

The segment BC of the cutting path is a curved segment having a relatively small radius which, it will be assumed, cannot be traversed at the maximum feed rate due to inertial loads and other inherent limitations of the cutting system. Furthermore, the accuracy with which the cutting blade tracks a desired line of cut depreciates where the feed rate is within the capacity of the system but, because of the contour of the line of cut and the rapid movement, deviations from the cutting path become intolerably large. Accordingly, the feed rate of the cutting blade defined by the tape program is reduced to maintain accurate tracking and, at the same time, the stroking speed of the blade is reduced to prevent fusion. When the blade reaches point C, however, a maximum feed rate command and a new stroking speed command are read by the controller 20 so that the blade then proceeds at high speed along the generally linear segment of the cutting path beyond point C.

in accordance with the above description, it will be apparent that a method of cutting a layup of sheet material is disclosed in which the stroking speed of the cutting blade is regulated in accordance with the feed rate along the cutting path and the feed rate is in turn determined primarily by the contour of the cutting path. The implementation of this method in hardware can be achieved by several means. As described above, the feed rate and the stroking speed commands are separately programmed on the memory tape 22 for processing by the controller 20 during the cutting operation. An entire data processing system which is capable of generating programs containing both the feed rate and stroking speed commands is shown in FIG. 4.

The cutting program is first established by preparing a marker 80.0r layout bearing the outlines of the pattern pieces arranged in the same manner that they will be cut from the layup. The marker is then placed on a digitizer 82 and the peripheries of the individual pattern pieces are traced either manually or by an automatic line follower so that point data defining the peripheries is generated as a series of digits which may be either transmitted directly to a data processor 84 or recorded on a tape for subsequent use by the data processor.

The data processor 84 is preferably a stored program computer which receives the point data and generates the cutting program as a series of basic commands intelligible to the controller 20. The basic commands are transmitted from the processor 84 to a recorder 86 which prints the commands on an initially blank memory tape 22. The tape is then installed in the tape reader of the controller 20 and the basic commands from the tape are translated into control signals that are transmitted during the cutting operation to the cutting mechanism 88 comprised of the drive motors, carriages, cutting table and blade of the apparatus 10 in FIG. 1.

When the data processor 84 receives the digitized point data, the stored program within the processor determines the feed rate and stroking speeds which are compatible with the cutting mechanism 88 and generates basic commands for the blank memory tape accordingly. FIG. is a flow diagram of one stored program subroutine for generating the feed rate and stroking speed commands. The entry point 94) of the subroutine receives input information including the digitized point data as a cutting program is generated. The firt matter determined in the subroutine is whether the cutting blade is up and out of engagement with the layup as indicated by block 92. if the blade is up, a reduced stroking speed command is caused to be recorded on the blank program tape as indicated at block 94. A reduced stroking speed when the blade is out of the layup reduces wear on the blade and the supporting components while no productive cutting is being accomplished. The reduced stroking speed is derived from one of several parameter cards 95 which are inserted into the data processor before the processor is started and which are imposed with the various pieces of information illustrated, including the reduced stroking speed desired when the blade is out of the layup. As shown at block 96, another matter determined when the blade is out of the layup is whether the displacement AX, AY is less than a predefined mount AD for example one inch, also derived from a parameter card. Even when the blade is out of the layup, it is desirable to reduce the translation rate or feed rate below the maximum rate when very short displacements are desired so that strain and wear on the cutting mechanism are reduced. if the displacement is greater than one inch, no feed command is given and the subroutine is then exited at block 98 without producing a basic command related to the feed rate. However, if the displacement is less than an inch, the feed rate commanded is proportional to AX, AY as indicated at block 104) and the subroutine is exited at block M1 2. It will be assumed that unless a feed rate command is recorded on the tape, the carriages l6 and 18 move the blade at the maximum feed rate.

If the blade 14 is down and in cutting engagement with the sheet material, a different logic path is followed as indicated at block 92. it has been mentioned with respect to the traversal of the cutting path P in FIG. 3 that several considerations relating to the geometry of the cutting path influence the rate at which the blade advances along the cutting path. One of these considerations is represented at block 104. If, as shown at point A in FIG. 3, the change in direction is greater than a preselected amount A taken from a parameter card, which requires lifting the blade, the feed is stopped and reduced stroking speed previously recorded on the parameter cards is imposed on the program tape to reduce the stroking speed until after the corner has been executed by the cornering subroutine concerning the lifting and rotation of the blade. The cornering subroutine may also provide a resume-stroking-speed-and-feed command to revert the feed rate and stroking speed to the maximums, assuming other conditions such as the length of the next segment are consistent with such command. if the feed is stopped and a reduced stroking speed command is generated at block 106, the subroutine is exited at block 108.

If the change in direction is less than A and, therefore, lifting and rotation of the blade are not necessary, further considerations bearing upon the feed rate and stroking speed are examined. In block 110 consideration is given to the length of the subsequent path segment and if this segment is less than a preselected amount AD such as one inch, taken from the parameter cards, a reduced feed rate and stroking speed proportional to AX, AY are outputed on the memory tape and the subroutine is exited at block 114 in much the same manner as the program was generated at blocks and 102.

Assuming still further that the conditions of blocks 104 and are not present, a further consideration concerning the subsequent segment of the cutting path is examined in view of the hardware limitations on the parameter cards as indicated at block 116. If for example the cutting blade is at point B in the cutting path of FIG. 3, a reduced feed rate and stroking speed along the path segment having the relatively small radius of curvature may be necessary in order to maintain accuracy and to stay within the capabilities of the hardware. Both the desired feed rate and stroking speed are derived from the information previously inserted in the data processor 3d on the parameter cards and the reduced rate and speed are commanded as indicated at block 118 before the routine is exited at block 120. It will be recognized that the stroking speeds commanded at blocks 106 and 1 18 may be the same or different depending upon the conditions that are to be satisfied as the blade advances along the cutting path.

If none of the conditions specified in

blocks

104, 110 and 116 are met when the blade is down, the subroutine is exited at block 122 and with no feed or speed commands programmed on the tape, the cutting blade will move along the cutting path at the maximum feed rate and a corresponding stroking speed.

In this manner a program tape bearing both feed rate commands and stroking commands is generated by the data processor 84 and recorder 86 When the controller 20 reads the basic commands from the program tape the cutting mechanism 88 causes the blade I4 to advance along the cutting path at variable feed rates and regulated stroking speeds in a cutting operation that is optimized to provide maximum utilization of the hardware without overheating or fusing the sheet material. While the variation of feed rates and stroking speeds is governed principally by the contour of the cutting path, the stroking speed generally changes with the feed rate. If the feed rate increases, the stroking speed also increases but notnecessarily in a proportional relationship since the displacement of the blade during one reciprocation cycle of the blade need not necessarily remain constant at all feed rates. In the same manner if the feed rate is reduced, the stroking speed is generally reduced also, although not necessarily in a proportional relationship.

FIG. 6 illustrates one embodiment of the cutting mechanism which is designed to operate from a memory tape which contains both feed rate and stroking speed commands programmed, for example, as described with respect to FIGS. 41 and 5. The controller 20 is connected to an X carriage motor drive 130, a Y carriage motor driver 132 and a -motor driver 134 to transmit motion commands for the cutting blade 14. The X driver 130 energizes the X drive motor 44 and in a corresponding manner the Y driver 132 energizes the Y driver motor 54 so that the composite X and Y motions produced by the

motors

44 and 54 cause the blade to be translated to any point over the table I2. In the same manner and at the same time the O-driver 134 energizes the 6-drive motor 64 to rotate the cutting blade and align it with the direction of the cutting path, assuming that the blade 14 is lowered into cutting engagement with the layup of sheet material. In accordance with the present invention, the controller also receives stroking speed commands from the programmed tape and applies stroking speed control signals to a stroke driver 136. The driver 136 is in turn connected to the stroking motor 70 and energizes the motor in accordance with the speed commands derived from the programmed tape.

FIG. 7 shows a modified embodiment of the present invention which operates independently of any stroking speed commands on a memory tape or which operates from tapes which contain no stroke speed information. In this embodiment of the invention only X-,Y- and 0-motion commands are transmitted from the controller 20 to the respective drivers I30, I32 and 134. The drivers energize their respective motors to produce the desired movement of the cutting blade 14 through the layup of sheet material in the same manner that the blade 14 is moved in the embodiment of FIG. 6. In FIG. 7, however, feed rate information is derived from the X and Y motion commands by an X feed rate tachometer 140 and a Y feed rate tachometer 142. With the feed rates along the principal coordinatesof motion of the cutting blade 14, a shaper circuit 144 calculates the composite feed rate, and a stroking speed signal determined in accordance with the composite feed rate is applied to the stroke driver 136 to regulate the reciprication speed of the stroking motor 70. The shaper circuit M4 may provide a selected minimum stroking speed at all times in order to execute sharp corners such as shown at point A in FIG. 3. The shaper may also be adjustable or be provided with a variable program so that the feed rate and stroking speed relationship can be varied for cutting different types of materials, some of which are more sensitive to heat than others.

While the present invention has been described in several preferred embodiments it should be understood that further modifications and substitutions can be had in both the steps of the method and components of the apparatus without departing from the spirit of the invention. In particular, the stroking speeds may be varied in magnitude by finite amounts by establishing a schedule of preselected stroking speeds for various feed rates and other cutting conditions along the line of cut. Alternatively, the speed rates may be regulated according to an infinitely variable schedule of stroking speeds so that the stroking speed of the cutting blade can be varied in a continuous manner as the cutting path requires. The above-described embodiments utilize a variable speed stroking motor and a fixed length stroke to change the stroking speed of the blade; however, the present invention can also be practiced by maintaining a constant reciprocation rate and varying the radius of the crank that produces the reciprocating motion. Although the variable motor speed results in a less complicated structure and is therefore preferred from a design standpoint, reduction of the blade stroke while maintaining a constant reciprocation speed will also result in generation of less heat between the blade and the sheet material. Still further, it is contemplated that cutting systems employing both a variable speed stroking motor and a variable stroke drive linkage can be utilized to practice the present invention. It is therefore apparent that the use of the term stroking speed refers not exclusively to the reciprocation rate of the cutting blade but encompasses the reduced relative velocity of the cutting blade and sheet material which accompanies a reduction in the length of the blade stroke. Accordingly, the present invention has been described in several preferred embodiments merely by way of illustration rather than limitation.

I claim:

1. Apparatus for cutting sheet material comprising: support means providing a work surface for holding sheet material to be cut in a spread condition; a reciprocating cutting tool in the form of a cutting blade having a sharpened cutting edge extending along one edge of the blade; controlled drive means connecting with the tool and the support means for advancing the tool and sheet material spread on the work surface relative to one another with the cutting edge of the blade generally perpendicular to and in cutting engagement with the sheet material; stroking means including an adjustable speed drive motor connected with the reciprocating cutting tool for drawing the cutting edge of the blade in cutting engagement with the sheet material cyclically in and out of the material at an adjustable speed as the tool and sheet material move relative to one an- L11" other; and. stroking control means including a motor driver connected to the adjustable speed drive motor of the-stroking means and operatively associated with the controlled drive mean's for regulating the adjustable speed at which the cutting edge is cyclically drawn in and out of the sheet material as a function of the rate at which the controlled drive means advances the tool and the sheet material relative to one-another.

2. Apparatus as defined in claim 1 wherein the stroking control means and the controlled drive means include a common program tape containing both feed rate information defining the rate at which the tool and thesheet material advance relative to one another and stroking speed information, the information providing increased stroking speeds at increased feed rates.

3. Apparatus as defined in claim 1 wherein the stroke control means includes rate sensing means for producing regulating signals in accordance with the rate of advancement of the tool and the sheet material relative .to

one another.

4. A method of cutting a layup of sheet material along a cutting path defining a pattern piece with a reciprocating cutting blade having a cutting edge extending in the direction ofreciprocation comprising: moving the reciprocating cutting blade and the layup relative to one another at a controlled feed rate to guide the cutting edge of the blade along the cutting path in cutting engagement with the layup; rotating the reciprocating cutting blade about an-axis extending in the same direction as the cutting edge to maintain the blade generally aligned with the direction of cut along the cutting path; and regulating the stroking speed of the reciprocating cutting blade as the blade is moved along the cutting path by increasing the stroking speed with increasing controlled feed rates in accordance with a predetermined schedule and decreasing the stroking speed with decreasing controlled feed rates also in accordance with a predetermined schedule.

5. A method of cutting a layup of sheet material as defined by claim 4 including the additional step of maintaining the length of the reciprocation stroke constant at each point along the cutting path defining the pattern piece.

6. A method of cutting a layup of sheet material as defined in claim 4 wherein the step of regulating includes establishing the same predetermined schedule of preselected stroking speeds varying in magnitude by finite amounts for both increasing and decreasing controlled feed rates, and changing the stroking speeds of the reciprocating cutting blade by finite amounts in accordance with said same schedule to achieve the preselected stroking speeds.

7. A method of cutting a layup of sheet material as defined in claim 4 wherein the step of regulating comprises establishing one infinitely variable schedule of stroking speeds for both increasing and decreasing controlled feed rates, and changing the stroking speed of the reciprocating cutting blade in a continuous manner in accordance with the one infinitely variable schedule to achieve various stroking speeds during the cutting operation.

8. A method of cutting pattern pieces from sheet ma terial comprising: defining a desired line of cut in the sheet material in accordance with the pattern piece desired; providing a cutting blade having a cutting edge extending along an edge portion of the blade; plunging the cutting blade into and through the sheet material to position the cutting edge in generally perpendicular relationship to the sheet material; moving the cutting blade and the sheet material relative to one another in a controlled manner to advance the cutting edge forward of the blade along the desired line of cut; cyclically stroking the cutting blade relative to the sheet material in a direction parallel with the cutting edge as the cutting edge advances along the desired line of cut; and controlling the stroking speed of the cutting blade as the cutting edge advances along the line of cut to coordinate the stroking speed and speed of movement along the line of cut by increasing the stroking speed with increasing speed of movement and decreasing the stroking speed with decreasing speed of movement.

9. A method of cutting pattern pieces as defined in claim 8 including the step of maintaining the stroke of the blade constant as the stroking speed varies.

l0.A method of cutting pattern pieces as defined in claim 8 wherein the step of controlling comprises changing the length of the stroke of the blade to achieve desired stroking speeds of the cutting edge.

11. A method of cutting pattern pieces as defined in claim 8 wherein the steps of moving and controlling comprise adjusting the speed of movement and the stroking speed of the cutting blade at different points along the line of cut in accordance with the line geometry.

12. The method of claim 11 wherein the step of adjusting more particularly comprises reducing the speed of movement and the stroking speed of the blade at

Claims

1. Apparatus for cutting sheet material comprising: support means providing a work surface for holding sheet material to be cut in a spread condition; a reciprocating cutting tool in the form of a cutting blade having a sharpened cutting edge extending alonG one edge of the blade; controlled drive means connecting with the tool and the support means for advancing the tool and sheet material spread on the work surface relative to one another with the cutting edge of the blade generally perpendicular to and in cutting engagement with the sheet material; stroking means including an adjustable speed drive motor connected with the reciprocating cutting tool for drawing the cutting edge of the blade in cutting engagement with the sheet material cyclically in and out of the material at an adjustable speed as the tool and sheet material move relative to one another; and stroking control means including a motor driver connected to the adjustable speed drive motor of the stroking means and operatively associated with the controlled drive means for regulating the adjustable speed at which the cutting edge is cyclically drawn in and out of the sheet material as a function of the rate at which the controlled drive means advances the tool and the sheet material relative to one another.

2. Apparatus as defined in claim 1 wherein the stroking control means and the controlled drive means include a common program tape containing both feed rate information defining the rate at which the tool and the sheet material advance relative to one another and stroking speed information, the information providing increased stroking speeds at increased feed rates.

3. Apparatus as defined in claim 1 wherein the stroke control means includes rate sensing means for producing regulating signals in accordance with the rate of advancement of the tool and the sheet material relative to one another.

4. A method of cutting a layup of sheet material along a cutting path defining a pattern piece with a reciprocating cutting blade having a cutting edge extending in the direction of reciprocation comprising: moving the reciprocating cutting blade and the layup relative to one another at a controlled feed rate to guide the cutting edge of the blade along the cutting path in cutting engagement with the layup; rotating the reciprocating cutting blade about an axis extending in the same direction as the cutting edge to maintain the blade generally aligned with the direction of cut along the cutting path; and regulating the stroking speed of the reciprocating cutting blade as the blade is moved along the cutting path by increasing the stroking speed with increasing controlled feed rates in accordance with a predetermined schedule and decreasing the stroking speed with decreasing controlled feed rates also in accordance with a predetermined schedule.

8. A method of cutting pattern pieces from sheet material comprising: defining a desired line of cut in the sheet material in accordance with the pattern piece desired; providing a cutting blade having a cutting edge extending along an edge portion of the blade; plunging the cutting blade iNto and through the sheet material to position the cutting edge in generally perpendicular relationship to the sheet material; moving the cutting blade and the sheet material relative to one another in a controlled manner to advance the cutting edge forward of the blade along the desired line of cut; cyclically stroking the cutting blade relative to the sheet material in a direction parallel with the cutting edge as the cutting edge advances along the desired line of cut; and controlling the stroking speed of the cutting blade as the cutting edge advances along the line of cut to coordinate the stroking speed and speed of movement along the line of cut by increasing the stroking speed with increasing speed of movement and decreasing the stroking speed with decreasing speed of movement.

10. A method of cutting pattern pieces as defined in claim 8 wherein the step of controlling comprises changing the length of the stroke of the blade to achieve desired stroking speeds of the cutting edge.

12. The method of claim 11 wherein the step of adjusting more particularly comprises reducing the speed of movement and the stroking speed of the blade at changes in direction of the line of cut.