US3693561A

US3693561A - Automatic edge guide mechanism for sewing machines

Info

Publication number: US3693561A
Application number: US43872A
Authority: US
Inventors: Peter Hrinko Jr; Irvin Krause; Nandor K Latincsics
Original assignee: Singer Co
Current assignee: SSMC Inc
Priority date: 1970-06-05
Filing date: 1970-06-05
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: GB1349994A; FR2096012A5; DE2126033A1

Abstract

An edge guidance system which permits an otherwise conventional sewing machine automatically to sew a work piece along a predetermined margin. The automatic edge guide mechanism has a margin guidance means including a sensor to sense edge of the work piece prior to sewing and a servomotor operative responsive to the sensor reversibly to drive a guide ring mounted parallel to the work surface and about the stitch forming instrumentalities of the sewing machine, which ring is alternately operative with the feeding mechanism to shift the edge of the work piece into marginal alignment.

Description

United States Patent- Hrinko, Jr. et a1.

AUTOMATIC EDGE GUIDE I MECHANISM FOR SEWING MACHINES Inventors: Peter Hrinko, Jr., Fair Lawn; Irvin Krause, Mountainside; Nandor K. Latincsics, Ringwood, all of NJ.

The Singer Company, New York, NY.

Filed: June 5, 1970 App1.No.: 43,872

Assignee:

US. Cl. ..ll2/l2l.ll, 112/102, 112/153, 112/204 Int. Cl. ..D05b 19/00, D05b 27/14 Field of Search ..1 12/153, 152, 136, 203, 204, 112/205,214, 77, 70, 102, 121.11, 121.24, 121.12,121.15

References Cited UNITED STATES PATENTS Bihler ..112/121.24 Prazak ..112/121.24

[15] 3,693,561 [451 Sept. 26, 1972 3,650,229 3/1972 Rovin ..112/153 X 3,139,051 6/1964 Story ..1 12/204 FOREIGN PATENTS OR APPLlCATlONS 13,073 8/1903 Switzerland ..1 12/204 572,466 1/1958 ltaly ..l12/204 Primary Examiner--H. Hampton Hunter Attorney-Marshall J. Breen, Chester A. Williams, Jr. and Harold Weinstein [57] ABSTRACT An edge guidance system which permits an otherwise conventional sewing machine automatically to sew a work piece along a predetermined margin. The automatic edge guide mechanism has a margin guidance means including a sensor to sense edge of the work piece prior to sewing and a servomotor operative responsive to the sensor reversibly to drive a guide ring mounted parallel to the work surface and about the stitch forming instrumentalities of the sewing machine, which ring is alternately operative with the feeding mechanism to shift the edge of the work piece into marginal alignment.

6 Claims, 16 Drawing Figures PATENTEDSEPZS 1972 SHEET 1 0F 3 INVENTORS Peter Hrinko Jr. Irvin Krause TTORNEY Nondor K. Lotincsics M} M SHEET 2 [IF 3 EHHII INVENTORS Peter Hrinko Jr. W Irvin Krouse Y Nandor K. Loflncsics A ORNEY PATENTEDSEP 26 I972 96* I, 4 24 28/ WITNESS AUTOMATICv EDGE GUIDE MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION Heretofore, various means and devices have been utilized to sew a work piece along a predetermined marginal 'edge.The sewn margin of a work piece may be manually controlled or a mechanical guide or turning post may be used as a reference point for guiding the workpiece. Also, various automatic devices may be used to maintain edge control of the work piece, such as l a pair of feed wheels being independently driven at variable speeds to effect simultaneous feeding and .turning of the work piece, or (2) the use of reversible variable speed turning wheels, singly and in pairs,

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved automatic edge guide mechanism for sewing machines which senses and guides the edge of the work piece alternately with feeding thereof to produce a sewn seam along a predetermined margin thereof, regardless of the curvature of the work piece, so long as the work piece is flat; and which clamps a substantial portion of the work piece about the needle axis for turning thereabout.

ltis also an object of the present invention to provide an improved automatic edge guide mechanism which overcomes the prior art disadvantages; which is simple, economical, and reliable; which mechanism may be eitherbuilt into or added as a retrofit attachment to an otherwise conventional sewing machine; which uses a guide ring mounted parallel to the work surface and about the stitch forming instrumentalities to be alternately operative with the feeding mechanism of the sewing'machine; which uses a guide ring to shift the edge of the work piece toward or away from the line of feed during nonfeeding of the work piece; which uses a margin guidance means reversibly to rotate the guide ring to shift the edge of the work piece toward or away from the line of feed during nonfeeding of the work piece; which uses a guide ring mounted on the presser bar and operatively connected to be reversibly shifted by a drive shaft parallel to said presser bar; which uses a drive shaft having a flexible coupling therein to maintain the parallel relationship between said shaft and the presser bar, while permitting the guide ring to be moved vertically with said presser bar; and which uses an alignment presser guide spaced from the presser bar along a hypothetical line parallel to the line of feed.

Other objects and advantages will be apparent from the following description of one embodiment of the invention and the novel features will be particularly pointed out hereinafter in the claims.

2 BRIEF DESCRIPTION OF THE DRAWINGS This invention is illustrated in the accompanying drawings in which:

FIG. 1 is a schematic representation of a sewing machine having the novel automatic edge guidance mechanism.

FIG. 2 is a fragmentary perspective view, partially in section, of the improved automatic edge guide mechanism, including the sensor, guide drive means and guide ring thereof. v

FIG. 3 is a front elevational view, partly in section, of the improved automatic edge guide mechanism mounted on the sewing machine.

FIG. 4 is a bottom plan view, partly broken away, taken along line 4-4 of FIG. 3.

FIG. 5 is an enlarged fragmentary elevational view, partly in section, of the guide ring, presser foot, and sensing means of FIG. 3.

FIG. 6 is a top plan view of the'sensing means, the throat plate and the feed dog taken along line, 6-,-6 of FIG. 5. I

FIG. 7 is a schematic representation of a block diagram of the edge guide mechanism including the servomotor loop and associated components.

FIG. 8 is a diagrammatic representation of a plan view of a portion of the improved edge guide mechanism showing a work piece being fed past the guide ring.

FIG. 9 is an elevational view, partly in section, of the guide ring engaging the work piece to orientate the same during nonfeeding thereof.

FIG. 10 is an elevational view, partly in section, of the work piece being advanced by the transitory motion of the feeding mechanism.

FIG. 11 is a top plan view of a diagrammatic representation of the work piece, having an outwardly curved edge, after feeding thereof, but prior to the next needle penetration.

FIG. 12 is a diagrammatic representation of a top plan view of the work piece shown in FIG. 11 after the next needle penetration and edge orientation of the margin thereof to place the work piece'in position for translation along the line of feed.

FIG. 13 is a schematic representation of the work 7 piece shown in FIG. 12 after translatory motion by the feeding mechanism along the line of feed.

FIG. 14 is a top plan view of a diagrammatic representation of the work piece, having an inner curved edge, after feeding thereof, but prior to the next needle penetration.

FIG. 15 is a diagrammatic representation of a top plan view of the work piece shown in FIG. 14 after the next needle penetration and edge orientation of the margin thereof, to place the work piece in position for translation along the line of feed.

FIG. 16 is a schematic representation of the work piece shown in FIG. 16 after translatory motion by the feeding mechanism along the line of feed.

DESCRIPTION OF THE INVENTION In the illustrated embodiment of the invention, the sewing machine shown in FIGS. 1, 2 and 3, may be of any conventional type such as a flat bed lockstitch machine driven by an electric clutch-brake transmitter (not shown) through a belt 22 which drives the various sewing mechanisms. The sewing machine 20 is mounted in the top of a leg-supported table 24 and has a frame 26 that includes a bed 28 having a standard 30 thereon, from which is cantilevered a bracket arm 32 having its opposite end terminate in a head 34 that overhangs the bed 28, as illustrated in FIG. 1. Stitch forming instrumentalities, generally designated as 36 are driven by the belt 22 at the handwheel 37, and include a needle bar 38 journaled for vertical reciprocation in bearing 40, shown in'FlG. 2, disposed in the bottom wall 42 of the head 34. The lower end of the needle bar 38 carries an eye-pointed needle 44 which is reciprocated along a vertical axis 46 by the needle bar 38 upon the operator actuating the transmitter lever 48 to successively drive the needle 44 into and out of a needle hole 50 of the bed 28, so as to concatenate the thread in a well-known manner to form the stitches of the stitch forming instrumentalities.

A drop feed mechanism is driven by the belt 22 through suitable shaft and linkage (not shown) to terminate in a feed dog 52 shown in FIGS. 3, 6, 9 and 10. The feed dog 52 is intermittently raised above the work support surface 54 to cause the work piece 56 to be advanced along the line of feed 58 in translation past the needle 44, which is out of the work during feeding, one stitch length at a time. A throat plate 60 and bed slide 62 provide access to the mechanisms within bed 28 in the area of the feed dog 52, as shown in FIGS. and 6. The throat plate 60 has a feed dog aperture 64 to permit the feed dog to rise above and fall below the work support surface 54, and the needle hole 50 so as to permit the needle 44 to be vertically reciprocated into and out of the bed 28, in forming the stitches therein. Additionally, the throat plate 60 has imbedded in the top surface thereof a sensing means 66 extending normal to the line of feed and in advance of the needle hole 50, for purposes more fully described hereinafter.

A presser mechanism 68 is shown in FIGS. 2 and 3, has a presser bar 70, the lower end of which, carries a presser foot 72. The presser bar is journaled in bushing 74, as illustrated in FIGS. 2 and 3, to place the presser bar axis 76 in parallel relationship with the needle bar axis 46. The presser mechanism 68 is biased by spring 78 towards the work support surface 54, by a spring 78 held captive about the presser bar 70 to exert a downward pressure thereon. The spring 78 pressure may be adjusted by a turn screw 80 threadably connected in the upper end of a head 34. The presser mechanism 68 may be placed in operative or inoperative position by means of manual actuation of the lever mechanism 82, one end of which, is affixed to the presser bar 70 as at 84. In the operative position, the presser foot 72 will be raised by the upward vertical movement of the feed dog 52 in its feeding of the work.

Except for the sensing means 66, the sewing machine described hereinbefore has been of substantially conventional design. Though the improved automatic edge guide mechanism of the invention may be built into a sewing machine, in this illustration it has been depicted as a retrofit attachment added to the sewing machine 20. The automatic edge guide mechanism, designated generally 86, includes three major components; the sensor means 66 which senses the edge of the work piece 56, the servo assembly 88 which combined with the sensor means and associated circuitry (not shown) defines a margin guidance means 90, diagrammatically represented in FIG. 7, and a guide ring assembly 92 connected to be operatively actuated by the servo assembly 88, which reversibly rotates the same to shift the edge of the work piece toward or away from the line of feed during non-feeding periods.

The servo assembly 88 and the guide ring assembly 92, including a flexible coupling 94 in the combination of said assemblies constitute the mechanical assembly or guide drive means 96, illustrated in FIGS. 2 and 3.

The operating principle in obtaining the automatic sewing of the work piece 56 along a predetermined margin in the'automatic edge guide mechanism 86 is intermittently to shift the edge of said work piece by rotating-the work piece in a controlled manner around the needle 44 so as to position successively a point on the edge contour one stitch length ahead of the needle at the required marginal distance from the point of needle penetration after said work piece is fedforwardly one stitch. In this manner, the work piece 56 is alternately corrected andfe d. Basically, the work piece 56 is angularly corrected or orientated with respect to the line of feed when the needle 44 is down, and translated forwardly when the needle 44 is up.

The mechanical assembly 96 has a lower bracket 98 shown in FIGS. 1, 2 and 3, which is fixedly clamped to the presser bar above the presser foot 72 by a screw 100 extending through a clamp arm 102 having a bent forward portion which wraps around the presser bar 70. The lower bracket 98 extends in a plane substantially parallel to the work support surface 54, and is formed by the connection of several plates which combine to journal the operative parts therein, and includes a lower plate 104 shown in FIGS. 2 and 3, having an annular front portion and a rearwardly extending extension arm. An annular cover member 106 encloses the top of the plate 104, and a cover 108 encloses the bottom thereof, with each of the covers connected to the plate 104 by threaded members 110. The clamp arm 102 extends rearwardly from the presser bar 70 in superposition to the extension arm of the lower plate 104. An arm 112 having a groove 114 formed in the end thereof remote from the presser bar 70 is connected upon the clamp arm 102 behind the presser bar 70.

A guide ring 116 shown in FIGS. 2 and 3 is journaled in the lower plate 104 by a ball bearing 118 held between the plate 104 and the cover 108. The guide ring 116 is disposed in a plane substantially parallel to the work support surface 54, and functions as a mechanical interface between the work piece 56 and the servo assembly 88. The guide ring has an annular row of teeth 120 shown best in FIG. 4 cut in the bottom surface thereof to provide a high friction contact with the work piece 56. The axis of rotation of the guide ring 116 is coincident with the axis 46 of the needle bar 38. Therefore, when the guide ring 116 is rotated while in contact with the work piece 56, the cloth will be rotated about the needle 44 so as to shift the edge as explained hereinafter. The guide ring 116 makes area contact with the work piece 56 so as to positively turn the same about the needle 44.

In order to actuate the guide ring 116, a gear 122 is pressed onto the upper end of the guide ring 116, and as best seen in FIGS. 3 and 4, which gear 122 is driven by a gear 124 that in turn is driven by the servo assembly 88. The gear 124 is mounted on a stub shaft 126 journaled in spaced bearings carried by the clamp arm 102 and the lower plate 104 on either side of the gear 124. The stub shaft 126 extends through an aperture 128 formed in the arm 112 to connect to the flexible coupling 94, as set forth more fully hereinafter. The

gears

122 and 124 have substantially the same diameter and form a drive ratio of l l.

The presser foot 72 is circular and fits within the inner diameter of the guide ring 116. The presser foot 72 is pin-connected to the lower end of the presser bar 70, as at 129, so as to permit the same to pivot in a limited manner wherein the front thereof may rise slightly from the horizontal plane in which the presser foot 72 normally lies. A lamp 130 is carried on a bracket 132 connected to the head 34 above the lower bracket 98 in superposition to the line of feed 58. The presser foot 72 may be made of any suitable material,

such as plastic, in which a quarter section 134 immediately above the sensing means 66 serves as a window and is made transparent plastic or glass, shown in FIGS. 2 and 4 to seat upon radial steps 136 formed in the presser foot 72. A needle hole 50a is formed at the center of the presser foot 72 in alignment with the needle axis 46 and the needle hole 50 in the throat plate 60.

The underside 138 of the presser foot 72 is at a higher differential vertical setting relative to the annular teeth 120 of the guide ring 116 so as to establish a predetermined distance, designated generally X," as shown in FIG. 5, which distance X" is several thousandths of an inch. The height differential between the presser foot 72 and the teeth 120 of the guide ring 116 enables the guide ring 116 to turn the work piece 56 during edge orientation thereof without interference from the presser foot 72 which is nonrotatable fixed to the presser bar 70. I

The lower bracket 98 is fixedly connected to the presser bar 70 and is free to move along the vertical axis 76 of the presser bar 70. As a result when the feed dog 52 raises above the throat plate 60, it will sandwich the work piece 56 between itself and the bottom surface 138 of the presser foot 72 causing the same to rise along with the presser bar 70 and the lower bracket 98 which carries the guide ring 116. When the feed dog 52 recedes below the throat plate 60, the spring 78 of the presser bar 70 urges the lower bracket 98 and the presser foot toward the support surface 54 until the guide ring 116 comes into contact with the work piece 56. Accordingly, the lower bracket 98, which is rigidly attached to the presser bar 70 is alternately lifted and dropped corresponding to the action of the feed dog 52. Of course, the motion of the feed dog 52 in rising and falling is synchronized with the vertical reciprocation of the needle 44 so that when the needle 44 is down the guide ring 116 is in position to clamp the work piece between its annular toothed face 120 and the throat plate 60. To insure proper turning of the work piece 56 the friction between said work piece and the throat plate 60 must be kept to a minimum to permit said work piece to slide on the throat plate responsive to the reversible rotatable motion of the guide ring 116. Since the guide ring 116 contacts the cloth along the annular tooth face 120 as shown in FIG. 9, said work piece is clamped substantially all around the needle 44 and wrinkling thereof is substantially prevented.

Referring to FIG. 10, there is a diagrammatic representation of the work feeding motion. When the needle 44 is up and out of the work piece 56, and the feed dog raises above the top surface of the throat plate 60, the work piece 56 is clamped between the feed dog 52 and the underside 138 of the presser foot 52. The feed dog 52 forces the presser foot up sufficiently to raise the annular toothed face of the guide ring 116 off of the work piece 56. The work piece 56 is now free to be advanced forwardly along the line of feed 58 by the translatory motion of the feed dog 52 which causes the work piece 56 to slide in the direction indicated by the arrow 139 along the undersurface 138 of the presser foot 72. Thereafter, feed dog 52 recedes below the surface of the throat plate 60 and the work piece 56 is clamped by the guide ring 116, as shown in FIG. 9, to initiate the shifting of the work piece 56 to align the edge thereof, before the next feeding cycle.

The mechanical assembly 96 includes an upper bracket having a lower plate 141 secured by threaded members 142 to the top surface 144 of the head 34, which has been machined perpendicular to the axis 76 of the presser bar 70 in order to assure proper alignment of the servo assembly 88 carried by the upper bracket 140. Two

vertical plates

146, 146 are connected, as by welding, at either side of the lower plate 141. The plates 146 are shaped in the form of an inverted L with the base connected to the lower plate 141 and the leg portion extending downwardly behind the head 34 with a bearing block 148 connected between the legs 146 at the lowest end thereof, as illustrated in FIG. 3. A top plate 150 is suitably connected across the vertical leg 146 and is substantially parallel to the lower plate 141. A servomotor 152 is mounted to the top plate 150 and is encased by a cover 154. A tachometer 156 is carried by a bracket 158 within the cover 154 and operatively connected to the servomotor 152 for purposes more fully described hereinafter. The servomotor as shown in FIG. 3 has a drive shaft 160 fixedly connected by a coupling 162 to an extension shaft 164 journaled in a bearing 166 mounted in the bearing block 148. The lower end of the shaft 164 is connected to one side of the flexible coupling 94. An extension arm 168 is connected across the vertical plates 146 behind the bearing block 148 and has a tongue 170 formed at the lower end thereof, which extends into and through the groove 114 of the extension arm 112, as shown in FIGS. 2 and 3.

The flexible coupling 94 operatively connects the servomotor 52 to the guide ring 116 through suitable shafts and gearing. In the preferred embodiment, the flexible coupling 94 is depicted as having a double universal, one universal 172 being at the top and one universal 174 being at the bottom respectively of the coupling 94, with a telescoping ball spline connection 176 therebetween. The flexible coupling 94 transmits little or no backlash, and more important, does not restrain the vertical up and down motion of the lower bracket 98. While it is highly desirable to have the axes of

shafts

126, 160 and 164 coincident to each other and also parallel to the axis 76 of the presser bar, the need for perfect alignment and true parallelism of the adjacent axes is eliminated by the use of the flexible coupling 94. Of course, any misalignment which is not otherwise compensated for, would interfere with the motion of the feed dog 52 and result in both impaired feeding and operation of the guide ring ll6.An additional support for the lower bracket 98 is provided by the interaction of the tongue 170 in the groove 114, to insure vertical stability of the lower bracket 98. A hypothetical line 58a could be drawn through the axis 76 of the presser bar 70, and the axis of the stub shaft 126 and the longitudinal line of the tongue 170, as shown in FIG. 4, which line would be substantially parallel to the line of feed 58. Accordingly, any misalignment which still occurs in the mechanical assembly 96, is compensated for by the flexible coupling 94.

The sensing means 66 is an electro-optical system which includes a sensor 178, shown in FIGS. 2,5 and 6, imbedded by cement in the throat plate 60 and protected from damage by a glass plate 180 covering the same. The sensor 178 is a p-n semiconductor bar which has an output current proportional to the amount of light striking it. The current is converted to a D.C. voltage level which is amplified and transmitted through suitable circuitry' as represented in the block diagram of FIG. 7 to give information of the edge position. The edge position information is used to control the servomotor 152. The sensor 178 is disposed in the throat plate, as shown in FIG. 6, normal to the line of feed 58 and forwardly of the needle by a distance approximately equal to one average stitch length. The lamp 130 shown in FIG. 3, is mounted in superposition to the sensor 178 and the amount of light striking it will depend on how much of the sensor is covered by the'edge of the material. The sensor can be biased at any point along its length to give a null read out, which would correspond to the desired margin, so that it is possible to have a theoretical error of zero. In the preferred embodiment, a reference or null point is defined as the point at which the output current from the sensor 178 is approximately equal to one-half of the total output current available from the sensor 178 when uncovered or receiving 'light across its complete surface. The reference margin on the work piece 56 is determined when the outer edge 210 of the work piece 56 is coincident with the reference or null point which will occur when the sensor 178 is one-half covered. In the preferredembodiment, the reference voltage is chosen to be a fixed positive voltage so that if the work piece 56 has a margin which covers less than one-half of the sensor 178, the output current will be higher than the reference voltage and the amplifier 194 will direct the servomotor l52to correct the margin by rotating the work piece 56 counterclockwise. Conversely, if more than one-half of the sensor 178 is covered by the work piece 56, the output current will be lower than the reference voltage and the amplifier 194 will direct the servomotor 152 to correct the margin by rotating the work piece 56 clockwise. This is so because the work piece 56 is rotated around the needle 44 when the needle 44 is down, then the work piece 56 is fed forward one stitch length. No correction of the work piece 56 takes place during this feed. Therefore, the edge of the work piece 56 one stitch length ahead of the needle 44, is the point that must be set in the required position. By placing the sensor 178 at a location approximating the average stitch length ahead of the needle 44, any resulting error due to changes in the stitch length are sufficiently small and within the acceptable tolerance. In operation, the sensor 178 will have a current output proportional to the amount of light striking the surface thereof. In other words, if the light intensity is constant, the current will be proportional to the sensor area not covered by the work piece 56. This current is converted into a D.C. voltage level which is fed through the sensor circuit (not shown) to the servomotor 152. The margin may be varied by changing the biasing voltage which is controlled by a selector switch 182 mounted in a control panel 184 as shown in FIG. 1. In this way, the margin range may be adjusted in suitable steps such as H] 6 ofan inch within the range of H1 6 inch to inch.

The marginal guidance means as represented by the block diagram shown in FIG. 7 includes the sensing means 66 and the servo loop 186 of the servo assembly 88. The sensing means 66 is composed of the sensor 178 and the associated process circuit represented by the block, designated generally as 188, which receives the D.C. signal from the sensor 178 and transmits it to the servo loop 186.

The servo loop 186 includes a modulator 190, preamplifier 192, power amplifier 194, DC. servomotor 152 and D.C. tachometer 156, each of which is represented by an appropriate block. The modulator 190 is an electronic switch which interrupts the signal from the process circuit 188 of the sensing means 66 to the servo loop 186. The function of the modulator. 190 is to synchronize the operation of the servomotor 152 with the position of the sewing needle 44 so that the servomotor 152 is only operative when the needle is down and in the work piece 56, during which time the feed dog 52 is below the surface of the throat plate 60. The modulator 190 is driven by a needle position sensor 196 located adjacent the handwheel 37. The needle position sensor 196 includes a light source 198 and a photo light sensor 200 which is connected to the electronic switch of the modulator 190 and render same operative during periods when light is received there by. The light source 198 continuously shines a beam of light as indicated by the arrow 202 upon the non-reflective surface of the hand wheel 37. An arcuate reflector 204 is affixed to the handwheel 37 at a location corresponding to the needle down position. The reflector 204 will bounce the beam of light 202 upon the light sensor 200, as indicated by the arrow 206, for approximately of the sewing cycle, which corresponds to the needle down position. The reflected light beam 206 activates the needle position sensor 196 which, in turn, signals the operation of the electronic switch of the modulator 190, to thus allow the signal from the sensing means 66 to pass through and operatively drive the servomotor 152. For the balance of the sewing cycle, the modulator will be off and the servomotor 152 inactive. For convenience, this part of the sewing cycle may be considered the needle up portion, and it is during the needle up portion of the sewing cycle that the fed dog 52 advances the work piece 56 in translation past the needle 44. The preamplifier 192 functions to vary the gain of the forward signal from the sensor 178 which passes through the modulator 190, and the feed back signal from the tachometer 156. The power amplifier 194 is a D.C. amplifier with a voltage gain of 10, and is used as a power stage to drive the servomotor 152. The servomotor 152 is a low inertia, high torque, printed circuit, DC. motor, and allows a relatively large stitch-to-stitch correction. The servomotor 152 response, in a saturated mode, is approximately 120 at 200 stitches per minute (SPM), 45 at 1,000 SPM, 36 at 3,000 SPM, and 10 at 5,000 SPM, stitch-to-stitch correction angle. The DC. tachometer 156 is coupled directly to the motor shaft as shown in FIG. 3. The tachometer 156 provides dynamic braking and system stability. The dynamic braking is especially important in the servo loop 186 because of the intermittent mode of operation thereof. In other words, the servomotor 152 is accelerated to drive the guide ring 116 in making the correction and thereafter decelerated to a complete stop for each stitch, while the needle 44 is in the work piece 56. It is apparent that the stitch-to-stitch correction is made in a very small increment of time. For example, at 4,800 stitches per minute, the correction must be made in approximately 5 milli-seconds. Therefore, this time constant must be proportionately small. In order to achieve this fast response, the system is designed to operate in a saturated mold of operation for as much a part of the cycle as possible. Consequently, the total gain of the system is high and the tachometer feedback was used to damp the system.

The servomotor 152 is reversibly rotated responsive to the signal transmitted within the servo loop 186 so as to rotate the correction ring 116 through

suitable gearing

122 and 124 in order for the correction ring 116 to shift the work piece 56, the edge of which has been previously sensed by the sensor 178, as is diagrammatically represented in FIG. 7. The modulator 190 may be likened to an electronic chopping switch, and is used to synchronize the operation of the servomotor 152 with that of the needle 44. In this manner, the marginal edge of the work piece 56 will be corrected by the guide ring 116 which is reversibly rotated by the servomotor 152 when the needle is down, and when the needle is up, the servomotor 152 will be inactive. The handwheel 37 is shown in FIG. 7 to be mechanically connected to be driven by the sewing machine which also includes at the other end thereof, the head 34.

When the needle 44 is down and has penetrated the work piece 56 as shown in FIG. 9, and the feed dog 52 has receded below the surface of the throat plate 60, the guide ring 116 clamps the work piece 56 between its annular toothed face 120 and the throat plate 60. The guide ring 116 is now in position to shift the edge 210 of the work piece 56 toward or away from the line of feed 58 as shown in FIG. 8, so as to move the edge 210 with respect to the sensor 178 until the signal emitted therefrom reaches the null point. The signal from the sensor 178 is transmitted to the servomotor 152 which actuates the gear 124 reversibly to drive the guide ring 116 to enable the edge 210 to be positioned upon the sensor 178 to establish the null read out, corresponding to the marginal distance of the edge 210 of the work piece 56.

FIGS. 11, 12 and 13, depict a diagrammatic representation of the stitch-by-stitch positioning of an edge 210a having a convex curvature. The sensor 178 is partially covered by the edge 210a and, as shown in FIG. 11, the axis 46 coincides with a stitch point 8,, which is in position after feeding but not yet penetrated by the needle 44. A dotted line 212 represents the marginal distance from the edge along which the line of stitches 214 is being sewn. The needle will-successively penetrate the points 8,, S S etc. However, in order for the marginal distance to be maintained, the work must be shifted after each increment of feed. Accordingly, as illustrated in FIG. 12, after the needle 44 has penetrated the point 8,, the point S which was not in marginal position in FIG. 11, is rotated in the counterclockwise direction indicated by the arrow 216 by the ring guide 116 into marginal position upon the line of feed 58, as controlled by the sensor 178. During this time the stitch is formed at the point 8,. The needle 44 reciprocated up and out of the work piece 56 which is now advanced as shown in FIG. 13 by the feed dog 52,

as indicated by the arrow 139, one stitch length in translation past the needle 44 along the line of feed 58 to place the point S upon the axis 46 of the needle. The next anticipated stitch point S is not yet in marginal position. Upon the needle 44 penetrating the work piece 56 at stitch point 8:, the cycle will be repeated to thus place the point S and subsequent .stitch'points upon the line of feed 58 in the manner described.

FIGS. 14, 15 and 16 depict the stitch-by-stitch correction of an edge 210k which has a concave curvature. In this representation, FIG. 14 shows the stitch point 8,, coincident with the axis 46 after feeding and prior to needle penetration. Simultaneously with needle penetration the ring 116 will rotate the work piece 56 clockwise as indicated by the arrow 218 responsive to the signal from the sensor 178 to place the stitch point S upon the line of feed 58, as shown in FIG. 15. Subsequent to the stitch formation, the work piece 56 will be fed as indicated by the arrow 139 in FIG. 16, one increment in translation past the needle so that the stitch point S is now coincident with the axis 46. Thereafter the cycle is repeated for stitch point S and successive stitch points.

In summary, the operation of the automatic edge guide mechanism 86 will be initiated by the operator placing the work piece 56 under the presser foot 72 and partially covering the sensor 178, whereby the work piece 56 is in position for the first stitch which will initiate the cycle and cause a needle 44 to penetrate the work piece 56. During the time the needle 44 is in the work piece 56, the sensing means 66 is active and will signal the servomotor 152 of the servo assembly 88 to cause the same to rotate clockwise or counterclockwise, as the case may be, to drive the guide ring "116 and cause the work piece 56 to pivot about the needle 44, whereby the edge 210 of the work piece 56 normal to the line of feed 58 will be shifted into marginal alignment at the location of the sensor 178 which is one stitch length forwardly of the needle. Subsequently, the needle 44 is withdrawn from the work piece 56 and the feed dog 52 will advance the work piece 56 on stitch length. Thereafter, the needle 44 again enters the work piece 56 and the cycle is repeated with the work piece 56 having its margin corrected alternately with being fed.

The control panel 184, shown in FIG. 1, has operator-actuated controls connected thereto which effect control of suitablecontrol circuits (not shown), which will act separately or in combination to enable the automatic edge guide mechanism 86 to operate. On-off toggle switch 220 controls the A.C. power to the trans mitter of the sewing machine 20. On-off toggle switch 222 controls the power to the marginal guidance means 90. On-off toggle switch 224 controls the power supply to the servomotor 152. The on-off toggle switch 226 will activate or deactivate the servo loop 186 without turning the full power off so that the servo loop 186 can be deactivated without turning the power off. The manual/automatic toggle switch 228 allows the operator to select the mode of speed control whereby the feed may be manually controlled by the operator in use of the foot or knee treadle, or by the automatic setting of the rotary switch 230 which establishes a preset maximum speed. The switch 230 acts to limit the maximum speed when the mode of operation is set at switch 228 in the automatic mode. The switch 230 will be set at a speed corresponding to the complexity of the edge contour to be sewn. Suitable additional controls and switches may be provided to insure the automatic operation of the edge guide mechanism 86 as set forth hereinbefore.

It will be understood that various changes in the details, materials, arrangements of parts and operating conditions which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention.

Having thus set forth the nature of the invention what is claimed herein is:

l. A sewing machine having a frame provided with a head and a work surface for a work piece, a needle bar journaled in the head and carrying at its lower end an eye pointed needle, a presser bar journaled in the head and carrying at its lower end a presser foot, a feed mechanism alternately operative with the needle to raise into work engaging relation .in opposition to the presser foot and feed the work piece held therebetween along a predetermined line, an automatic edge guide comprising:

a. a sensing means mounted in front of the needle to sense the edge of the work piece approaching the needle,

b. a guide support member affixed to the presser bar,

c. a guide ring rotatively mounted and alternately operative with respect to the feeding mechanism in the guide support member substantially parallel to the work surface and surrounding the needle, and

d. a guidance drive means operatively connected to the guide ring reversibly to rotate the same to shift the edge of the work piece toward or away from the line of feed responsive to the sensing means 12 signal thereto,

e. the guidance drive means including a servomotor, a drive shaft driven by the motor and a gear train driven by the shaft reversibly to rotate the guide ring,

f. the drive shaft being disposed substantially parallel to the presser bar, i

g. the guidance drive means being mounted on the head, and

h. said shaft including a universal coupling interengagingjhe presser foot whereby said shaft, is Shl ta le 1n the X,Y and Z" plane of motionto -eliminate binding or misalignment.

2. The combination claimed in claim 1 wherein:

a. the guide ring is normally disposed in parallel relationship to the presser foot and in a horizontal plane a predetermined distance below the presser foot to permit the guide ring to shift the work piece without interference from the presser foot.

3. The combination claimed in claim 1 wherein:

a. the guide ring is coaxial with the needle which upon penetrating the work piece, defines a turning center about which the work is shifted.

4. The combination claimed in claim 1 wherein:

a. the guide support member has an arm extending horizontally therefrom remote from the presser bar, and

b. an arm affixed to the head extend vertically therefrom to interconnect with the arm of the support member to permit the support member to move vertically but to prevent horizontal shifting thereof.

. The combination claimed in claim 4 wherein:

. one of the arms has a tongue formed on the end thereof,

b. the other arm has a groove formed on the end thereof, and

c. the tongue and the groove engage one another to permit relative vertical movement of the support member and to prevent horizontal shifting of said support member.

6. The combination claimed in claim 4 wherein:

a. the shaft is disposed intermediate the presser bar and the pair of interconnected arms, and

b. the presser bar, the shaft and the pair of interconnected arms are disposed in a line parallel to the line of feed.

DUI

Claims

1. A sewing machine having a frame provided with a head and a work surface for a work piece, a needle bar journaled in the head and carrying at its lower end an eye pointed needle, a presser bar journaled in the head and carrying at its lower end a presser foot, a feed mechanism alternately operative with the needle to raise into work engaging relation in opposition to the presser foot and feed the work piece held therebetween along a predetermined line, an automatic edge guide comprising: a. a sensing means mounted in front of the needle to sense the edge of the work piece approaching the needle, b. a guide support member affixed to the presser bar, c. a guide ring rotatively mounted and alternately operative with respect to the feeding mechanism in the guide support member substantially parallel to the work surface and surrounding the needle, and d. a guidance drive means operatively connected to the guide ring reversibly to rotate the same to shift the edge of the work piece toward or away from the line of feed responsive to the sensing means signal thereto, e. the guidance drive means including a servomotor, a drive shaft driven by the motor and a gear train driven by the shaft reversibly to rotate the guide ring, f. the drive shaft being disposed substantially parallel to the presser bar, g. the guidance drive means being mounted on the head, and h. said shaft including a universal coupling intermediate the ends thereof to permit the presser bar, guide support member and guide ring to be raised and lowered by the feed mechanism intermittently engaging the presser foot whereby said shaft is shiftable in the ''''X,Y and Z'''' plane of motion to eliminate binding or misalignment.

2. The combination claimed in claim 1 wherein: a. the guide ring is normally disposed in parallel relationship to the presser foot and in a horizontal plane a predetermined distance below the presser foot to permit the guide ring to shift the work piece without interference from the presser foot.

3. The combination claimed in claim 1 wherein: a. the guide ring is coaxial with the needle which upon penetrating the work piece, defines a turning center about which the work is shifted.

4. The combination claimed in claim 1 wherein: a. the guide support member has an arm extending horizontally therefrom remote from the presser bar, and b. an arm affixed to the head extend vertically therefrom to interconnect with the arm of the support member to permit the support member to move vertically but to prevent horizontal shifting thereof.

5. The combination claimed in claim 4 wherein: a. one of the arms has a tongue formed on the end thereof, b. the other arm has a groove formed on the end thereof, and c. the tongue and the groove engage one another to permit relative vertical movement of the support member and to prevent horizontal shifting of said support member.

6. The combination claimed in claim 4 wherein: a. the shaft is disposed intermediate the presser bar and the pair of interconnected arms, and b. the pResser bar, the shaft and the pair of interconnected arms are disposed in a line parallel to the line of feed.