US 3080836 A
Description (OCR text may contain errors)
March 12, 1963 J. E. CLEMENS ETAL AUTOMATIC WORK GUIDANCE MECHANISMS 9 Sheets-Sheet 1 Filed March 9, 1961 In ven fora 1757a: ECZemens RayWHczrr uff Ben E. *JEhnszone 'iZ5D7u36Z) 2c y Mark .D. 15060 iike .HbraGe W Weeks .351 t/zez rflfiormgl March 12, 1953 J. E. CLEMENS ETAL 3,080,836
AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 2 March 12, 1963 Filed March 9, 1961 in VI 1 sTzEmNq J. E. CLEMENS ETAL AUTOMATIC WORK GUIDANCE MECHANISMS 9 Sheets-Sheet 3 March 12, 1963 J. E. CLEMENS ETAL 3,080,836
AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 4 Mardl 1963 J. E. CLEMENS ETAL 3,030,836
AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 5 March 12, 1963 J. E. CLEMENS ETAL 3,080,836
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AUTOMATIC WORK GUIDANCE MECHANISMS 9 Sheets-Sheet 7 Filed March 9, 1961 .5 Z: wurmjait NHBOAP u m h FE: wmflhsuiwuu L March 1963 J. E. CLEMENS ETAL 3,030,835
AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 9 \\\\\\III///// Z United State Patent? 3,080,836 AUTOMATIC WORK GUIDANCE MECHANISMS John E. Clemens and Ray W. Hermit, Xenia, Ben B.
Johnstone, Dayton, James 1). Ray, Wilmington, Mark D. Sobottke,'Kettering, and Horace'W. Weeks, Dayton, Ohio, assign'ors to United Shoe MachincryCorporation, .Flemington, NJ, a corporation of New Jersey Filed Mar. 9, 1961, Ser. :No. 94,556 26 Claims. .(Cl; 112-457) lected course, for instance substantially parallel to prescribed curvature such as that of an edge of the material even though this edge be of changing curvature. .Although the invention as herein illustrated is embodied in a sewing machine wherein the reciprocable tool is in the form of a needle for securing a binding strip in parallel edge relation to a shoe part, it will be understood that in its various aspects the invention is :not thus limited either as to materials employed, the nature of the function performed, is. a securing or sewing operation, or to the particular machine which is shown merely by way of example, it being .rccognized that the invention has utility in a wide variety of machines which may employ different types of tools.
Hand controlled steeringof Work pieces in a machine becomes tedious and inaccurate when they are irregular in shape and non-rigid, and the path of operation of a tool thereon must, at least in part, be other than rectilinear. Also, the production capability of a machine in which such work pieces are being manually fed is likely 'to be somewhat reduced, it has been observed, when the operating path of the tool involves a sharp or reverse 'curve and engagements of the tool with the work tend to interrupt its feeding movement. Accordingly, efforts have been made to provide guidance mechanism which, unlike the more cumbersome control means developed in the machine tool industry for orthogonally moving work-carrying tables, is adapted automatically to steer sheet material by action taken directly on the work itself. One approach, for instance, is that disclosed in an application for United States Letters PatentSerial No. 827,970, filed July 17, 1959, in the names of Hans F. Schaefer, Jr.,
and Robert K. Jenner, Jr, now Patent No. 2,979,745, and
another is disclosed in an applicationSerial No. 27,214, filed May 5, 1960, in the names of William S. 'Iouchman and Loyd A. Barnes, now Patent No. 3,034,781. The
former, relating to anedge folding machine, is briefly distinguished in that its work guidance is effected by a pair of spaced members exerting torque for automatically swinging the work about only one turning center located substantially at or near its edge, whereas in the latter case, exemplified in a skiving machine, the work steering means may cause the instantaneous center of turning to be shifted along a known line. Work guidance as ali'orded by these developments and for their range of application has been found to relieve the burden on an operator While facilitating production of his machine.
In the light of the foregoing it is a general object of this invention to provide, in a machine including a tool for operating at successive localities on a work piece, improved means operative at only a single work engaging locality for automatically and intermittently guiding the work piece with respect to the tool to cause its operating path to extend along a preselected course, for example,
2 inparallelrelation to'theedge of the work. Another and considerably more-specific object of this invention is to provide a machine for automatically and progressively securing as by means of a seam, in-edge to edge relation, the-upper of a shoe and a .piece or strip such as an edge binding. ln accordance with these objects and as illustrated herein, a feature of this invention resides in the combination, ina maehine having a reeiproeable work e-n-' gaging tool and :mechanism for feeding the work inthe intervals when the tool is disengaged, of "independent means automatically effectivebetween said feeding intervals ,predetermin'edly to steerthe work by turning it about its locality of engagement with the tool, thesteerin'g means being responsive -to selected curvature such as that of the periphery of the work just ahead of the tool. While the tool may, for instance, be an actuated punch, fastener inserter, embosser or marking 'tool, or other instrument of movable type for physically operating on the work, it will be a preciated "that the'term tool" as herein used is intended also "to comprehend non-moving eleiifeirt's ar- 'r-anged'to engage the Wb'ik'tb' trea't-it, examples or such elements being a cement applyin nozzle, 2 burnishin member or the like. In the illustrated machine the esemplary "tool, as "above stated, is a reciproc'able needle,
and hence the work steering means of this invention preferably operate solely while the needle is penetrating "a work piece toe'xert forces for bodilyfpivotirig the latter only about the needle in its successive work engaging localities. Advantageously, the work steering means is adapted 'to be installed in a sewing or other machine of otherwise conventional construction, the illustrated post sewing machine incorporating a common form of orbital dog feeding mechanism for advancing the work instepby-step translation in the intervals when the needle is withdrawn from the work. In partial resemblance to'the above-mentioned Schaefe'r et a1. disclosure, the present steering means includes a servo-controlled reversible, variable speed steering wheel, the presentnovel construction, however, in a simple and unique manner, avoiding any necessity for providing a mechanism for this wheel which must differentially allow for the transl'at-ory feed speed as effected by the feed dog and its cooperative presser foot. 7
A further feature of the invention consists in the provision, in a machine having an operating tool and feed means cyclically operative to advance the work by in- 'crements, of improved automatic work steering means including only a single steering wheel and a presser member which is arranged to be moved into and out of cooperative Work engaging position inwardly of the feed means from the tool, the mounting of the steering means being such that its operation is responsive to that of the feed means and automatically effected alternately therewith. Advantageously, this construction permits a servo motor controlling velocity of the wheel to operate with zero error during straight line feeding of the 'work in translation. As herein shown the feed presser foot prefer ably is a roll carried by a usual vertical, downwardly urged, presser post, and the steering presser member is preferably a roll carried by a lever pivotally connected to the presser post and spring-urged into operative position. Thus, advantageously, the steering wheel may be continuously driven regardless of the relative position of the steering presser roll, this position being determined by that of the feed presser roll, and the controlling servo motor being continuously responsive to changes in selected governing curvature such as edge curvature of the work at a locality immediately ahead of the operating zone of the needle.
The above and other features of the invention, including means for automatically changing incremental teed 3 n or stitch length without interrupting operation of the machine, and means for sensing a selected work corner automatically to effect stopping of the machine or simply discontinued steering but continued feeding (for instance as a new work piece is being introduced to the machine),
together with other novel combinations and arrangements of parts will now be more particularly described in connection with an illustrative machine and with reference to the accompanying drawings thereof, in which:
FIG. 1 is a view in front elevation of a post type sewing machine, at rest, for securing binding strips to articles such as shoe uppers and in which this invention is embodied;
'FIG. 2 is a view in front elevation, partly in section, showing on a larger scale and in operating condition the sewing machine head and post together with automatic work guidance means including :a steering wheel and cooperative steering presser roll;
FIG. 3 is a. view in side elevation of mechanism shown in FIG. 2;
FIG. 4 is a view in front elevation showing operating instrumentalities including a needle as indicated in FIG. 2, on a further enlarged scale, portions being in section to illustrate actuating means for the steering presser roll;
FIG. 5 is a section taken on the line VV of FIG. 3 indicating the mountings of a feed presser roll and the steering presser roll;
FIG. 6 is a plan view of the work supporting post indicating the relative positions of the work steering wheel and a throat plate assembly accommodating the sewing needle, a feed dog, and control cells with reference to an adjustable null line and work piece;
FIG. 7 is a section taken on the line VII-VII of FIG. 6 extending through a needle hole;
FIG. 8 is a graph comparing the torque required to turn a given leather work piece in the machine with the torque available from the steering wheel in a cycle of operations;
FIG. 9 is a view in front elevation, with a portion broken away, of the right hand side of the machine and showing stitch length change mechanism;
FIG. 10 is a detail of an axial part in the stitch length change mechanism;
FIG. 11 is a section, on a larger scale, taken on the line XI-XI of FIG. 9;
FIG. 12 diagrammatically indicates a work piece portion having an edge of inside curvature at which stitch length, merely because of such curvature, normally is increased;
FIG. 13 shows the sa-me edge as shown in FIG. 12 but with stitch length reduced actually to provide more uniformity in stitch length appearance and an increased number of stitches at the curvature;
FIG. 14 is an end elevation, partly in section, illustrating means for automatically stopping the machine with its needle in up position, the parts being shown in position when the machine is stopped;
FIG. 15 is an end elevation corresponding with the upper portion of FIG. 14;
FIG. 16 is a section taken on the line XVI-XVI of FIG. 14;
FIG. 17 is a block diagram of the work guidance system and associated electric machine controls;
FIG. 18 is an electrical diagram of power amplification and preamplification units as connected between the guidance cell and a servo motor;
FIG. 19 is an electrical diagram complemental to that of FIG. 18 and showing motor and bias supply controls; and
FIG. 20 is an alternate form of steering presser foot as mounted for cooperation with the steering wheel of this machine.
General Organization In many respects, unless otherwise noted herein, the sewing machine illustrative of the invention is of a commercially available construction and conveniently adaptable to receive automatic work guidance means as will be described. It comprises a hollow frame 22 (FIGS. 1-3) secured on a bench 24 and having a vertically r..- ciprocable needle 26 (FIGS. 1-4). In guiding the work in the machine by the exercise of this invention and without operator attendance once the work has been presented. the operating path of the needle on the work may be caused, as will be explained, to extend in any selected course. For purposes of illustration a work piece, such as an upper U (FIGS. 1 and 6) of a shoe, is automatically guided with respect to the needle 26 to cause the stitches of a seam to extend parallel to a work piece edge thus securing an article such as a binding strip S (FIGS. 1 and 3) in parallel edge relation. The needle is disposed to be received in a needle hole 23 (FIG. 6) of a bobbin cover or throat plate 31 screwed onto the upper end of a composite machine post 32 (FIGS. 1-3 and 6) upstanding from the bench 24. As usual for operating the needle the frame 22 supports in bearings a horizontal main shaft 34 (FIGS. 3 and 9) operat-ively coupled to a needle post 36 (FIGS. 1-5) vertically reciprocable in a bore formed in an overhanging head 38 of the frame 22. The main shaft 34 and an orbitally actuated feed dog 40 (FIGS. 3, 4 and 6) are driven from a main DC. motor 42 (FIGS. 1, 9, 17 and 19) through mechanism subsequently described.
It will be understood that the feed dog 40 intermittently rises above the level of the supporting surface of the throat plate 39 to feed the work step-by-step in translation past the needle in the intervals when the latter is disengaged from the work, the direction of feed being from right to left in FIG. 3 or from bottom to top as viewed in FIG. 6. For cooperating with the feed dog a feed presser roll 44 (FIGS. 2, 4 and 5) is carried by an end of an arm 46, the other end of which is secured to a bracket 48. This bracket is fixedly mounted by means of a setscrew 50 (FIG. 5) on the lower end of a presser foot post 52 (FIGS. 3, 4 and 5 arranged for movement in a vertical bore formed in the head 38. In usual manner the feed presser roll 44 is yieldingly urged toward workengaging position when the post 52 is in its lower position. a spring 54 (FIG. 3) having its lower end bearing on a bracket 56 afiixed to the post and an upper end abutting a sleeve 58 adjustably threaded in the head 38. A hand lever 60 (FIG. 3) pivoted to the head at 62 has an end surface 64 disposed to engage a horizontally projecting portion of the bracket 56 as the lever is turned clockwise as viewed in FIG. 3 for the purpose of raising the post and the feed presser roll 44 from the work. As indicated in FIG. 3 by dotted lines the surface 64, when horizontal, latches the post 52 in its upper and inoperative position. Work-engaging pressure of the roll 44 may be modified by suitably turning the sleeve 58, some slight pressure normally being desirable for a given thickness of the work even while the dog 40 is in lowered position and disengaged from the work, though this pressure should not be enough to affect work guidance by means hereinafter explained.
A reel 66 (FIG. 1) for holding a supply of the binding strip S to be sewn to the shoe upper U (FIG. 6) is rotatably mounted in a holder 68 removably secured to the machine head. The strip extends downwardly through a guideway 70 (FIG. 1, 3 and 5) formed on the front end of a bracket 72 secured to the presser post bracket 48, the exit end of the guideway being disposed somewhat ahead of the needle hole 28 and laterally spaced to aline an edge of the strip with a peripheral edge of the upper in the locality about to be stitched, both edges then being close to, if not exactly in, tangency with a null line L (FIGS. 5 and 6) determined by automatic guidance means next to be explained.
Automatic Work Guidance System in an upright wall 86 (FIGS. 2 and 3) Within the machine post .32 and hasan upper portion of its toothed periphery projecting through a slot 88 (FIG. 6) of the post for frictional engagement with the underside of the upper U. As best shown inFIG. 6 the wheel 80 is thus arranged to engage the work at a locality spaced farther inwardly of the work from the needle operating zone than is the feed dog 49, the work engaging localities of the needle, dog, and steering wheel lying substantially in a line normal to the null line L. For operating the wheel 80 a bracket 90 (FIGS. 2 and 3) secured to the underside of the top of the bench 24 mounts a housing 92 for suitable reduction gearing (not shown) having output shafts 94, 96 which are universally coupled. Accordingly, the servo motor 84 together with its stabilizing tachometer generator 98 (FIGS. 17, 18) is mounted on the housing 92 reversibly to drive the shaft 96 and a bevel gear 100 on the upper end thereof which meshes with a bevel gear 102 formed coaxially on the steering wheel 80.
The curvature sensing means above referred to for continuously governing speed and direction of the servo controlled steering wheel 80 is, in this case, arranged to sense curvature of the edge of the upper itself at a locality "just ahead of that about to be acted upon by the needle 26. The means comprises electrical circuitry including a light sensitive device in the form of a work sensing or guidance solar cell 1% (FIGS. 6, l7 and 18) embedded in the throat plate Bil, a DC. bias supply unit generally designated 110 (FIGS. 17 and 19), a preamplifier unit generally designated 112 (FIGS. 17 and 18), and a power amplifier unit generally designated 114. Location of the cell 1% is critical to servo motor stability and important to derive accurate steering or error signals. Preferably the cell is spaced within a range of from substantially zero to five feed increments ahead of the needle hole 28, the best location usually being within about one feed increment and hence closely adjacent to the operating path of the needle 26. Also, considered transversely of the null line L, the cell 103 is disposed so that, when the operating locality of the upper is correctly oriented with respect to the needle, about one-half of the cell is covered by the \VOIli piece acting as a shutter, and the other half of the cell 1638 is exposed to light beams directed from a source above, such as a bulb 116 (FIGS. 1, 2 and 4) mounted on the bracket 48 or, if preferred, simply dependent from the head 38. By reason of change in curvature of the work piece edge at a point closely adjacent to the operating locality as the upper is fed past the needle, the cell 1138 is more or less covered by the upper U. Accordingly, a DC. voltage from the curvature detecting cell, generated when the cell is covered exactly to the null line L by the upper, is directed to one leg of a resistance circuit within the preamplifier unit 112 and nulled by application of a DC. voltage, equal in magnitude and polarity, from the bias supply 11% to a second leg of the resistance circuit, a third leg of this circuit including a variable resistor 118 (FIG. 18) having a manual control 120 (FIG. 1) for fine adjustment of the null point or line L as desired. The electrical null and consequently the null line L are established by the fact that voltages equal in magnitude and polarity are present in the two resistance circuits in the preamplifier 112 and that the electromechanical chopper unit of the preamplifier 112 alternately reads the voltage present in the two resistance circuits. The electromechanical chopper unit of the preamplifier 112 directs these voltages to .a coupling capacitor 121 (FIG. 18) of the preamplifier 112 which filters the chopper ripple signal, which is undesirable particularly at the servomotor null point, to give only a system reference voltage and therefore .no neter-ror signal. Each increment of feed is therefore likely to change the voltage present in the resistance circuit connected to the cell 168 and thereby createsa net voltage diiference as seen by the capacitor 121 constituting an error signal. The servomotor 84 is dependent upon error signal voltage phasing for direction of rotation information. This informationis supplied by virtue of the vfact that the net voltage difference producing the error signal must .be larger than the system reference voltage and that this difierence may alternately appear at the elecvtromechanical chopper contact, connected to bias supply resistance circuit, or the contact connected to the cell 108 resistance circuit, as the cell 108 is either covered more or uncovered more. This signal, which is now an .A.C. signal by virtue of the electromechanical chopper, is amplified and is passed through a contact K1C1 (FIG. 18), when closed, to a functional control box generall designated .122 (FIGS. 1, 17 and 19). The contact K101 is closed by actuation of a foot switch 124 (FIGS. 1, 1.7 and 19) to energize a relay coil K1 shown in FIG. 19 and, in fact, mounted on the chassis for the preamplifier 112. After appropriate switching in the functional control box 122 the error signal is fed tothe power amplifier unit 114 and ultimately to the servo motor 84 itself. As will be understood by those experienced in servo control art, the so-called pure error thus derived is modified in known manner for damping purposes by employing the tachometer generator '98 to add a rate of change of error signal, the addition being effected by a variable resistor and a summingresistor in the preamplifier unit 112. Also, in known manner, other components of the preamplifier unit enable the servo motor 84 to achieve maximum power by insuring the voltages in its control and reference winding are in quadrature.
As has been indicated, while the steering wheel 80 is continuously operative and hence always potentially able to exert a steering torque on the work, it desirably is actually elfective toguide or steer the work only when the needle 26 has penetrated, in this case, the upper and strip S and can thus serve as the pivot or instantaneous center of turning about which the work is bodily swung by the wheel. For thus causing the steering to be effected alternately with each increment of feeding, and synchronously with successive work engagements of the needle, mechanism next to be explained is provided for automatically causing the steering presser roll 82 to be urged into an effective torque exerting position of greater cooperative work engaging pressure and then retracted to a substantially ineffective position wherein its work engaging pressure is minimal permitting slippage of the wheel 80 and substantially no effective guidance torque. Experiments have shown that the wheel 80 will 'slip on most upper leather, for instance, when the guidance torque is reduced to about 10 inch-ounces or less (see FIG. 8). The roll 82 is carried on the front end of a lever (FIGS. 3 to 5 inclusive) pivotally secured by a fulcrum pin 132 to the bracket 48. The rear end of the lever 130 is connected by means of a tension spring 134 to the lower end of a stud 136 adjustably threaded heightwise in a tubular support 138 secured to the machine head 39. A knurled head 14% of the stud 136 may be rotated suitably to modify the clamping pressure (and consequently the torque level before slippage) exerted by the steering presser roll 82 according to the severity of curvatures involved in the operating path of the needle and with regard to the character of the material to be guided. A collar 142' (FIG. 4) pinned on the stud 136 aids in guiding it heightwise in the support 138 which is vertically slotted at .144
. as shown in FIGS. 1 and 2 to accommodate the lever 130.
feeding is emphasized because it economically enables the guidance system, after each feeding increment, bodily to turn the work to the correct degree about the work engaging needle and until the full error signal is nulled or reduced to zero; hence upon upward retraction of the needle the thread of the stitch next to be inserted following the feeding increment will lie in accurately parallel relation to the work edges. It will be understood that when the feed dog 40, acting through the work, lifts the feed presser roll 44 in the course of a feeding increment, the steering torque available from the wheel 80 is reduced substantially as shown in FIG. 8 since resultant raising of the presser foot post 52 and of the fulcrum pin 132 relieves the upward force exerted by the spring 134 and hence correspondingly reduces the work-engaging pressure of the steering presser roll 82 to allow ineffectual rotation of the wheel 80. Consequently the required servo response frequency is not equal to the incremental feeding frequency of the feed dog 40 but is only a function of the equivalent frequency as generated by the radius of curvature and the average peripheral speed of the work. Thus, the required servo response frequency may be many times less than the incremental feeding frequency. Considered further with reference to FIG. 8, when the feed dog 40 is being lowered at the end of a feeding increment, the wheel 80, by reason of the now increasing work clamping pressure exerted by the spring 134 through the steering presser roll 82, is ready and able to exert a steering torque theoretically limited only by the output of the servo motor 84.
Machine Drive Mechanism In addition to the automatic work guidance system described, the illustrative machine includes in highly advantageous combination therewith and as parts of its drive mechanism next to be considered means generally designated 148 (FIGS. 9-11 and 15) for changing stitch length, particularly in the course of traversing sharper inside curvatures such as shown in FIGS. 12 and 13, without interrupting operation of the machine, and a device generally designated 150 (FIGS. 9, 14 and 16) for autornatically stopping the machine with its operating tool, the needle 26, in up or inoperative position. First with regard to the means 148, the main shaft 34 is hollow to receive a conically ended portion 152 (FIGS. and 11) of an axially slidable operating shaft 154 (FIGS. 1, 9 and 11). The latter as indicated in FIGS. 14 and 16 extends axially through a hand wheel 156 keyed on the shaft 34, and through parts of the device 150 comprising a earn 158 rotatable on a reduced hub of the hand wheel, a pulley 161) to which the cam 158 is keyed, a cam plate 162 straddling the cam, and a guide plate 164 having opposed, parallel walls 166, 166 for radially guiding the cam plate 162 as displaced by the cam 158. The guide plate 164 is bored to receive a pair of pins 168, 168 (FIG. 16) for securing the plate 164 to the hand wheel. A pulley 170 (FIG. 9) on the drive shaft of the motor 42 is fitted with an endless belt 172 for transmitting power to the pulley 160. For changing stitch length at the will of the operator, he shifts the shaft 154 to the right as viewed in FIG. 9 by any suitable means, a knee pad 174 (FIGS. 1 and 9) being provided in this case for this purpose. Thus actuation of the pad to turn its carrying lever 176 counterclockwise as viewed in FIG. 9 about a fulcrum 178 provided by a bracket 180 secured to the bench operates linkage including an arm 182 of a lever 184, and a link 186 connecting the arm 182 to the lower end of a long vertical lever 188. The upper end of this lever 18$ is pivoted to a bracket 19% (FIGS. 1, 9 and secured on the main frame, and is connected by trunnion pins 192, 192 to a collar 194 afiixed on the shaft .154. This shifting of the shaft 154 is elfected against resistance of a return spring 1% connecting the bench and the lever 184.
Referring mainly to FIGS. 9 and 11, actuation of the pad 174 axially to shift the conical portion 152 as just described causes this portion to bear on the rounded end of a plug 193 adjustably threaded into an enlarged hub portion 266 of an eccentric 202, the plug extending radially through a bore formed in the wall of the main shaft 34. Accordingly, the hub portion 2%, which is mounted on a pivot pin 204 projecting from a flange of a collar 265 secured on the shaft 34, is urged counterclockwise as viewed in FIG. 11 by means of a spring pressed plunger 2518 hearing on the shaft 34 at a locality diametrically opposed to the plug 198. The eccentric 202 is therefore shifted to a position of greater concentricity with the shaft 34 to the limit adjustably permitted by a short stitch adjusting setscrew 210. For this purpose the screw 210 extends into one end of an arcuate slot 212 (FIG. 11) formed in the hub portion 202 for endwise engagement with a stop screw 214 threaded through the flange of the collar 266 at a locality diametrically opposite to the pivot pin 204. The displacement to lessen eccentricity of the eccentric 262, it will be understood, is effective to shorten the stitches by reason of shortening the throw of a connecting rod 216 (FIGS. 3 and 9) for rocking a customary sewing machine feed shaft 218 (FIG. 3) horizontally mounted in the bench 24. As usual a crank 229 secured on the shaft 218 causes a lever 222 (FIG. 3) to impart feeding movements in translation to the dog 40, its heightwise movements being concurrently imparted by a rotary cam 224 working in a forked arm 226 of the lever 222.
FIG. 11 depicts the screws 210, 214 in their operating positions, for instance before negotiating the curvature indicated in FIG. 13, where the stitches have been shortened and hence adjustably increased in number. Without means to change to shorter stitch length at sharper inside curvatures it is found that their length is, in fact, otherwise lengthened as shown in FIG. 12 thereby producing unsightly, nonuniform appearance in the product. Shorter stitch length at such curvature yields better construction and a binding of better appearance, for instance, when the strip S is later folded over. Re lease of the pad 174 permits the spring 196 to restore the normal stitch length without interrupting operation of the machine, the stop screw 214 then abutting a long stitch adjusting screw 228 (FIG. 11) threaded through the portion 292 and into the opposite end of the slot 212.
Coming now more especially to the device for stopping the machine in needle-up position, it is essential for decreasing the operating time of a machine cycle and permits the work always to be correctly located in the machine before commencing automatic operation. The device is adapted to terminate rotation of the main sha t 34 in a position corresponding to that in which it has raised and retracted the needle 26 from the work. A motor control unit generally designated 230 (FIGS. 1, 17 and 19) includes a variac 232 (FIG. 19) for changing AC. voltage applied to a rectifying bridge 234 which, in turn, provides a DC. voltage to the motor 42 as selected by means of a knob 236 (FIG. 1) for thus controlling variable speed of the motor. The latter is energized for operation at the preselected speed by the actuation of the foot switch 124 to energize relays K2 and K5 (FIG. 19), resultant AC. voltage being applied to a rectifier bridge 238 through a contact KSAI and directed as DC). voltage through contacts K2A1 and K2A2 to the motor. Cutting off of the motor drive voltage by means of the device 159 as now explained stops the shaft 34 in the desired position. Upon release or opening of the foot switch 124 the relays K1, K2 and K5 are deenergized, and a relatively low AC. voltage is accordingly applied to the rectifier bridge 238 through a now closed contact KSBI (FIG. 19). This gives rise to a DO. reversing voltage being applied to the motor 42 through now-closed contacts K251 and K2B2. Accordingly, when the machine has stopped and its main shaft 34 starts to reverse (i.e. turns in the clockwise direction indicated in PEG. 14), the camplate 162 is outwardly displaced radially until its projection 24% (FIG. 14) depresses a striker 242 rpivotally carried by a lever 244 itself pivotally secured on a pin 245 in a bracket 246 which is afiixed to the right-hand end of the machine frame 22. The arrangement is such that a projection 248 (FIGS. 9 and 14) on the lever 24d consequently opens a switch 250 (FIGS. 9, 14 and 19) removing all motor drive voltage immediately to stop the machine in needle-up position. Better to understand this operation of the device it is pointed out that the earn 158 is formed with a rise 2'52 extending over an arc of 60. During forward or sewing operation of the shaft 34 (counterclockwise rotation as viewed in FIG. 14), the torque required from the cam 158 reacts against an internal wall 254 of the cam plate 162 causing it to retract inwardly in the guide plate 164 with the switch operating protection 240, the latter then being ineifectual while pivoting the projection 24% clockwise (as viewed in FIG. 14) against resistance of a spring 255 which normally holds the striker against a stop 257 formed on the end of the lever 244. When fully retracted, the cam 158 is in driving or forward feeding engagement with the internal cam plate wall, but upon motor reversal as has been stated, the earn 158 acting upon an internal wall 256 of the plate 162 quickly displaces the projection 248 outwardly consequently depressing the striker to switch-opening position. it will be apparent from FIG. 14 that the switch 25%} is permitted to assume its normally closed position during machine operation by a spring 1258 connecting the lever 244 to the bracket 246, the spring serving to urge the striker 242 into position to be engaged by the projection 2% upon motor reversal.
Work Controls Adjwnctz've to Guidance System As shown in FIG. 1 the control box 1'22 (FIGS. 1, l7 and 19) in which the bias supply control 126 is mounted also includes a manual stop switch 262 and a rotary selector switch 264. The latter is advantageously empioyed to select any preferred one of four modes of operation of the machine next to be explained according to whether this switch is turned to its position 1, 2 or 3 indicated on the box 122. in switch position 1, used for normal operation, the machine drive and work guidance is controlled solely by the foot switch 124 as deseribed. The second mode is foilowed when it is desired to have operation of the machine automatically stop at the end of each work piece, i.e. at the finish the throat plate 39 immediately ahead of the guidance cell Hi8 and preferably disposed parallel to the operating path of the feed dog 4i). Referring to P16. 19, in practicing this automaticwork kick out, a switch S2 now being closed, a switch S3 being open, and a switch S4 being closed at position B, the foot switch 124 is held depressed to cause the machine to operate as previously described, the motor 42 continuing to run by virtue of energization of a relay K3 and consequent closure of a contact K3A1 which parallels the foot switch. When the seam being inserted has been guided past some selected corner, for instance the next to last one, the operator will release the foot switch 124, and a voltage is thereby applied to a transistor amplifier 268 and to a coil K4, the machine continuing to function under the automatic work guidance system. Now, by action of the cell 255, upon bein uncovered by the work at its next, i.e. last, corner, an added voltage surge is applied to the relay K4 via the transistor amplifier 268, and the relay K4 then opens a contact K4B1 (FIG. 19) to deenergize the relay K3 thereby removing the motor drive voltage to stop the machine with its needle in up position. it will be appreciated that this second mode of operation provides added freedom for an operator; he may, during the final stage of automatic guidance'on one work piece, as soon as he has released the foot switch, reach for the next piece to be processed for instance, being assured that the machine will automatically cease operation at the correct point, for example at the locality where the seam was initially started.
In a third mode of operation now to be explained and termed the kick off function, the selector switch 264 is also at position 3. This mode is used in connection with peripheral operations when it is desirable to terminate operation of the machine at any point along the operating path other than at a corner. When the point is reached a manual kick olf switch 272 (FIGS. 1 and 19) is actuated. This results in a signal being transmitted via the closed contact B of the switch S4 to a line designated D and hence to the power amplifier 114 causing the servo motor forthwith to steer the work away from the operating zone. This is to say that the resultant overriding command tothe servo motor requires the wheel 3b to rotate to turn the work rapidly clockwise (as viewed from above) about its own centroid. The machine consequently stops when it has thus caused the work to render the cell 266 exposed to light from the bulb 116.
A fourth mode of operation is advantageous in speeding up output, particularly when smaller work pieces are being processed, and is termed the kick through arrangement. For this purpose the selector switch 264 is adjusted to position 2 (FIG. 1) causing the switches S2; S3 (FlG. 19) to be closed, and a contact A of the switch S4 to be closed while its contact B is open. in this mode the main motor 42 is permitted to run continuously as the work pieces are successively guided and sewn, one directly following completed guidance of another. relays K1, K2, K3 and K5 are energized by actuating the switch 124 and the motor 42 drives by virtue of the closure of the contact KBAI. Prior to reaching the feed out corner the switch 124 is released to energize the coil K4 and the transistor amplifier 268. As the kick out cell 266 senses the end of each work piece (in the manner described for the second mode), the cell applies a surge through the transistor amplifier 268 further to energize the coil Kd and close a contact K t-A2. As a result power is now fed from an independently powered circuit including a potentiometer 274 (FIG. 19), via the contact lid-A2 and the line D, to the power amplifier 114 instead of an input from the preamplifier M2, the velocity of the wheel thus being modified to permit the feed dog it to operate forthwith to feed the work in a substantially straight line away from the operating zone. Now, when the operator presents the next work piece thereby again covering the cell 266, the contact KdAZ opens and the contact K4-B2 closes to transmit the normal guidance error signal from the preamplifier 112. To stop the drive motor 42 the switch 262 must be actuated when the series of work pieces has been processed.
FIG. 26 illustrates an alternate type of steering presser in the form of a bowed or U-shaped spring 2% which may be substituted for the steering presser roll 82 in frictionally exerting, cooperatively with the steering wheel 86, suitable steering torque on the work. The spring ass is secured at its ends to a horizontal bracket 282 fast on the head 38, lies in a vertical plate, and has a mid portion 234 movable heightwise in yieldaole work engaging position. The width of the spring portion 284 is preferably at least as great as that of the toothed perirneter of the wheel 86 and, notably, is yieldable in trans F lation parallel to the direction of feeding. If desired, of
11 course, opposed margins of the portion 284 may be rounded upwardly from the work. For automatically guiding work having certain physical characteristics or combinations thereof (hardness, roughness, resiliency, variable thickness, flexibility, etc.), it is believed the spring 80 will assist in overcoming adverse influence on steering due to work distortion or slippage. As shown in FIG. 20, to facilitate presentation and removal of the work, the portion 284 is mounted to be movable heightwise together with the feed presser roll 44 by the post 52. Thus, a yoke 286 attached to the portion 284 is connected by a coil spring 288 to one end of a lever 29%, the other end of which is pivotally secured by a screw 292 to a block 294 clamped on the post 52. Means including a vertical set screw 296, a pivotal lever 298, and an eccentric cam 30% manually adjustable by a control knob 302 are provided for obtaining differential in operating pressure between the feed presser roll 44 and the spring 28%.
Machine Operation It will be understood that the machine is provided with a supply of thread T (KG. 1) for the line of sewing to be inserted by the needle 26 as determined by the automatic work guidance mechanism above described. Also, it will be understood the usual shuttle mechanism (not shown) is mounted in the post 32 and operated from a drive belt 394 on a pulley 306 (FIG. 9) secured on the main shaft.
By use of the knob 236 the operator will first have selected the motor speed with which the seam is to be inserted. Having connected the machine and controls to their respective power sources an operator places the upper to be sewn on the machine post 32, lowers the presser foot post 52 by means of the lever 60, and, while ascertaining that the end portion of the strip S is extending suitably from the exit of the guideway 70, holds the extremity of the thread T for the first stitch as he actuates the treadle 124. Without further attenion the sewing machine then continues to operate, alternating steps of translatory work feeding and automatic steering, the latter being dictated by the curvature of the work edge, until the work piece has traversed the desired course and is automatically ejected. The resultant seam securing the upper and strip in parallel edge relation will extend parallel to the edge the curvature of which is being sensed by the cell 138. Feeding in straight line translation is effected by the dog 40 in approximately half the machine cycle, the other half being used at least in part for steer ing by means or" the wheel 80. In the steering intervals, which normally occur only when the needle has engaged the work to serve as a turning center therefor, the wheel 80 is caused by the servo motor 84 to rotate with a torque frictionally applied to the work. A servo motor could conceivably be electrically controlled so that its output would be synchronized in a cycle with the work engaging phase of the needle, but since this appears to necessitate theme of unduly expensive equipment, this invention provides for the servo motor 84 continuously to receive steering signals, but at practically no added cost effectively couples the output of the servo motor to the work via the wheel 89 only while the needle is engage This is accomplished by making use of the heightwise movement of the feed dog 40 to control alternation of feeding and steering. Thus, when the feed dog moves up to feed, it acts to lift the work off the steering wheel 8%, or (if the work be less stiff) acts through the post 52 to reduce the pressure with which the work is engaged at its steering locality by the wheel St so that the latter then rotates harmlessly and is temporarily ineffective. On descent the dog returns the work to be coupled to the wheel 80 for steering about the now engaged needle.
During the automatic guidance of the work with respect to the needle, the curvature sensing cell 1% continuously responds electrically to the degree of light incident from the source its not intercepted by the work 12 and thus produces a signal, which varies from the DC. reference voltage from the bias supply 110, which corresponds with deviation of the controlling curvature, in this case the work edge, from its correct position. Accordingly, a signal in terms of DC. voltage is derived to be converted to an AC. signal which, when amplified and damped as explained, is fed to the servo motor S4. The latter therefore reversibly and continuously drives the steering wheel 36 in the proper direction and with correct speed potentially to apply a moment to the work U to restore it to its correct or zero error position after each increment of feed in translation effected by the dog 40.
Considered analytically, operation of the machine will vary according to the requirements of particular work, it being helpful in some cases to provide the steering presser roll 82 and/ or the wheel 8% with a periphery of a rubberlike, friction-enhancing material. In the illustrative machine a short interval may occur in the cycle in which it is possible that, although the needle 26 is still descending or has just descended into the work, the wheel 86 may be exerting a low torque but be ineffective to steer the work by reason of the fact that the dog 40 is still engaging the work with sufiicient clamping pressure to cause the wheel 89 simply to slip. It should be noted, however, that the preferred timing and organization is not such that work clamping pressure of the feed means, i.e. the dog 40 and the roll 4-4, is capable of exerting torque to steer the work either about the needle or the work engaging locality of the Wheel 80. In other words, as indicated in FIG. 8, the feeding and steering portions of a cycle are normally exclusive, steering occurring only when the necdle engages the work, and feeding occurring only when the needle is disengaged or at least causes no appreciable drag. Slight exception may occur in some machines when there advantageously is a very brief overlapping of the feeding and steering functions by reason of a small work engaging pressure being allowed to be exerted during steering time by the feed presser, for instance where feeding is phase dispaced from needle motion. The feed presser is then providing a light drag or pivot to enable the needle to pierce the work just before the feed stroke is com- .plete; in this situation the needle is still out of the work when steering action commences.
In conjunction with the automatic work guidance means provided, the several control features above explained have been found particularly helpful, both individually and collectively, to the operator. Thus, by l cans of the device 156 the needle 26 never interferes with proper loading or removal of the work from the machine, the mechanism depicted in H6. 14 operating as explained, reliably to lift the needle from the work almost instantly when the treadle 124 is released to stop the machine. Also, during continuous operation of the machine on the work being automatically guided, it is found advantageous to employ the stitch-length changing mechanism at a selected portion of the operating path. As explained with reference to the FIGS. 9-11, the operator only needs to actuate the knee pad 174 as the selected portion (the sharp inside curvature of FIG. 13, for instance) approaches the operating zone of the needle, to shift the shaft 154 axially to the right (in FIG. 9) and thus shorten stitch length. This makes for a stronger seam in a critical area and produces a more uniformly stitched article.
Selection of one of the three settings 1, 2, or 3 for the selector switch 264- enables the operator to have the work automatically guided in the machine to the selected ejection or stop position. As above explained, the resultant circuitry causes kick-out, kick-through, or kickoff. In the kick-out mode, the switch 264 being in position 3, the operator simply releases the switch 124 as the work is being guided to cause the next or final corner to approach the ejection control cell 266. Upon this corner uncovering the cell 266, it causes the drive motor voltage to be cut off and the machine to stop in needle 13 up position, the work being ejected if it was the last corner traversing the cell 266. Normally, of course, the switch 124 may be released at any time simply to stop operation of the machine.
In the kick-through mode, the switch 264 being at position 2, when the foot switch 124 is released the machine continues its normal automatically guided sewing until the next (normally last) work corner advances and sufficiently uncovers the cell 266, whereupon the dog 40 feeds the work straight from the needle to permit the next piece of work to be presented thereto without interrupting operation of the machine. The kick-01f mode permits immediate feed-out of the work upon manual operation of the switch 272. It will be understood that the thread T and strip S will be severed as convenient to provide the individual, assembled work pieces.
Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:
I. In a machine having a tool for operating on a work piece, mechanism intermittently operative to feed the work piece an increment in translation past the tool, and
edge curvature controlled means adapted to initiate and exert a steering torque on the work piece and about the operating locality of the tool each time the feeding mech anism has operated to determine the operating path of the tool on the work piece.
2. 'In a machine having a work support, a relatively movable tool for opera-ting on successive portions of a. Work piece on the support, means for feeding the work intermittently in translation with respect to the tool, a work sensing circuit, and automatic guidance means continuously responsive to said circuit and frictionally operable in time relation to the work feeding means for controlling steering movement of the work piece with respect to the tool.
3. In a machine having a work support provided with an operating zone and on which a work piece is intermittently advanced in translation one step beyond said zone, a relatively movable tool cooperative therewith at the operating zone by engagement with successive portions of a work piece, automatic guidance mechanism including a member frictionally engageable with the work piece at only a single locality spaced from the tool for steering the Work piece with respect thereto, and means for causing said guidance mechanism effectively to operate when the tool is operative in said zone.
4. In a machine having a tool for operating on successive portions of a work piece, a work support on which the work piece is to be guided with respect to the tool by operation of work feeding means and work steering means, said feeding means including a member having components of movement both heightwise and in translation, curvature sensing means for controlling said work steering means, and mechanism responsive to one of the components of motion of said member for effectively operating the steering means alternately with the feeding means.
5. ins machine having a tool for operating on or near the margin of a Work piece and means for feeding the work piece step-by-step past the tool, mechanism engageable with the work piece at one locality only for steering the work with respect to the tool according to the curvature of the work edge in the operating locality of the tool, and means for effectively operating said steering mechanism alternately with said feeding means.
6; A machine comprising a tool for operating on the margin of a Work piece, means operable inwardly of the work piece from the tool for feeding the work piece stepby-step past the tool, mechanism including a steering member and cooperative presser member operative at only a single locality farther inwardly of the work piece from the feeding means for steering the work piece with work edge immediately ahead of the tool, and means for 1a effectively operating said steering mechanism when said feeding means is inoperative.
7. In a machine comprising a tool adapted to engage successive marginal portions of a work piece and having means for advancing the work piece past the tool each time the tool is retracted therefrom, work steering means including a steering member and a presser member cooperatively engageable with opposite sides of the work piece inwardly of its margin, means for controlling the steering member according to marginal curvature of the work in a locality just ahead of the tool, and mechanism responsive to operation of the work advancing means for controlling relative movement of the steering and presser members into and out of cooperative work-em gaging positions whereby the work steering means is effective bodily to turn the work about the tool only when the tool is in engagement therewith.
8. In a machine comprising a tool engageable with the margin of a work piece and having means for intermittently advancing the work piece past the tool, work steering means engageable with opposite sides of the work piece at only a single locality inwardly of its margin, said steering means being continuously responsive to the curvature of the margin in its portion immediately ahead of the tool, and mechanism for rendering said steering means effective in each interval that the work piece is not being advanced, reversibly to swing the work piece about a turning center substantially at the zone of engagement of the tool therewith.
9. In a machine having a reciprocable tool for operating on a work piece and comprising work feeding means including a first presser member for feeding the work past the tool, automatic work steering means including a second presser mem er spaced from the first, and control means operative in time relation to the operation of the tool for alternately shifting the presser members into and out of efiective engagement with the work whereby the work is alternately fed and steered.
10. In a sewing machine having a reciprocable needle and a throat plate formed with a hole for receiving the same, an orbitally actuated dog for feeding the work past the needle istep-by-step, and automatic work steering means including only one pair of work-engaging members for bodily turning the work about the needle when the latter has penetrated the work.
11. A machine as set forth in claim 10 further characterized in that electrical means is provided for con trolling the velocity of one of said members in accordance with change in curvature.
12. A machine as set forth in claim 11 and further characterized in that the electrical means includes a circuit comprising a light responsive device arranged in the throat plate ahead of the needle by a spacing in the range of substantially from zero to five feeding steps, and said one member is a wheel reversibly rotatable according to the curvature of an edge of the work.
:13. In a machine having a reciprocable tool for operat' ing on successive portions of a work piece, a work support over which the work piece is to be fed and guided with respect to the tool to cause its path of operation to extend in parallel relation to the edge of the work piece, a feed member movable heightwise of the work support for intermittent engagement with one side of the work piece to feed it in translation when the tool is retracted, a presser arranged to cooperate with said feed member by engagement with the work piece on its opposite side,
mounting means for said presser yieldingly to effect its.
work engagement during tool retraction, and work guidance mechanism comprising a continuously operative steering wheel and cooperative steering presser arranged, respectively, to engage the work piece inwardly of the feed member, the velocity of said wheel being controlled by sensing means responsive to change in curvature of said edge in the vicinity of the tool, and the steering presser having operative connection to said mounting means acsaeee whereby the guidance mechanism is effective to pivot the work piece about the tool only when it engages the Work piece.
14. A machine having a reciprocable tool for operating on successive increments of sheet material, comprising mechanism operable to advance the sheet material rectilincarly an increment between successive engagements of the tool with the material, guidance mechanism operable for exerting torque on the material at only a single locality spaced from said engagements of the tool, curvature monitoring means for controlling the potential torque to be exerted by the guidance mechanism, and means for causing said torque actually to be imparted by the guidance mechanism to the sheet material only when the latter is being engaged by the tool.
15 in a machine having a tool for operating on successive portions of a work piece, means for feeding the work piece rectilinearly an increment between the succersive operations of the tool, and guidance mechanism operative simultaneously with the tool bodily to turn the work piece about the operating zone of the tool when the latter is in engagement with the work piece, said mechanism including a servomotor continuously responsive to signals generated from a controlling pattern.
16. A machine as set forth in claim 15 and further characterized in that the guidance mechanism comprises only one member reversibly driven with variable velocity in frictional engagement with the work piece, the velocity of the member corresponding with the concurrent deviation of the curvature of said pattern from the preceding rectilinear feeding increment whereby torque exerted by the member on the work piece seeks to reduce such deviation to zero.
17. In a sewing machine having a reeiprocable needle, 2. throat plate having a needle receiving hole over which work to be sewn is to be guided, means including a member movable heightwise of the throat plate for feeding the work an increment in translation each time the needle is retracted therefrom, work steering means including a wheel and cooperative presser engageable with the work under variable pressure at a single locality spaced from the operating path of the needle and close to the work supporting surface of the throat plate, a curvature sensing circuit including a light sensitive device embedded in said plate surface immediately ahead of the needle hole for controlling the velocity of the wheel, and mechanism responsive to the heightwise motion of said feeding member for causing the wheel and the presser to engage the work with greater pressure while the needle is available to serve as a pivot therefor.
18. A sewing machine as set forth in claim 17 and further characterized in that said circuit includes a biased power supply for determining a null line along which zero steering error occurs, and means for shifting the null line transversely of the direction of feeding.
19. In a machine of the type having a work support, a tool movable toward and from an operating zone on the support to engage successive portions of a work piece thereon, and means movable relatively to the support to advance the work piece in translation past the tool while it is inoperative thereon, the combination comprising guidance mechanism for exerting variable torque on the work piece at a single locality close to the surface of said support, said mechanism comprising a servo-controlled steering wheel the work-engaging perimeter of which is disposed adjacent to said surface and a presser cooperative with said perimeter, means for actuating the presser toward the perimeter with greater pressure while the tool engages the work piece, said actuating means comprising a yieldingly pivotal lever for carrying said presser and having operative connection to said work advancing means, a curvature sensing circuit for continuously controlling the velocity of the steering wheel, said sensing circuit including a light sensitive device disposed closely adjacent to the operating zone and transversely of a null lb line, and a source of light disposed in the vicinity of said Zone and on the opposite side of the work piece from said device.
20. In a machine having a tool for operating on successive portions of sheet material of irregular curvature, mecharnsm for feeding the material in increments past the tool, work guidance mechanism including a light sensitive cell responsive to curvature of the material in a locality just ahead of the operating zone of the tool, a tubular main shaft for driving the tool, operating connections including eccentric means on the shaft and by which said feeding mechanism is driven, a collar rotatable with the main shaft and providing a pivot for said eccentric means, and a rod shiftable axially within the main shaft during operation of the machine to change the eccentricity of said eccentric means to modify the length of the feeding increments upon sharp change in said curvature approaching the cell.
21. In a sewing machine having stitch forming devices and means for feeding a work piece in translation intermittently past these devices, a partly tubular main shaft having operative connections, respectively, for driving said means and devices to insert a seam of normal stitch length, automatic guidance means responsive to edge curvature of the work piece in a locality immediately ahead of the devices for controlling steering of the work with respect thereto, said operative connections to the work feeding means including a strap cccentrically receiving the tubular portion of the main shaft, mechanism shiftable axially of the latter to modify the eccentricity of the strap, and control means operable as sharper edge curvature approaches the device for thus shifting the mechanism to change the stitch length from normal during negotiation of the sharper curvature and then back to normal without interrupting operation of the machine.
22. In a machine having a tool for operating on a flat work piece of irregular edge curvature, mechanism for feeding the work piece in translation with respect to the tool, electrical means including a light sensitive device responsive to rays directed past the work piece for steering the latter according to its curvature and in time relation to said feeding mechanism, and control means including a second light sensitive device located immediately ahead of the first-mentioned device for causing the steering means at a selected corner of the work to permit the feeding mechanism to move the work piece in a straight direction away from the tool.
23. In a machine having a tool adapted to operate along the margin of sheet material, means for feeding the material in translatory increments past the tool, mechnism for applying a steering torque at a single locality to guide the material with respect to the tool according to the curvature of said margin, and a control circuit including a light sensitive device arranged ahead of the tool and energizable upon being increasingly uncovered by a portion of the margin automatically to stop operation of the machine.
24. In a machine having a tool adapted to operate along the margin of sheet material, means for feeding the material in translatory increments past the tool, mechanism for applying a steering torque at a single locality to guide the material with respect to the tool according to the curvature of said margin, said mechanism including a curvature sensing circuit comprising a servomotor, a power amplifier connected to the motor, and a preamplifier from which sensing signals are normally transmitted to the power amplifier, and a control circuit energizable at the will of the operator to send an overriding command to the power amplifier whereby the scrvomotor abruptly causes the guidance mechanism to apply a torque for ejecting the material from the operating locality of the tool.
25. In a machine having a tool adapted to operate along the margin of sheet material, means for feeding the material in translatory increments past the tool,
mechanism for applying a steering torque at a single locality to guide the material with respect to the tool according to the curvature of said margin, said mechanism including a curvature sensing circuit comprising a servomotor, a power amplifier connected to the motor, and a preamplifier from which sensing signals are Y normally transmitted to the power amplifier, a control circuit including a light sensitive device disposed ahead of the tool and energizable upon being increasingly uncovered by a portion of the margin, and a second control circuit normally disconnected from the power amplifier and having an independent input, the arrangement being such that when said device is thus energized said second control circuit provides an input to the power amplifier in lieu of that from the preamplifier whereby said feeding means is permitted to feed the material in a substantially straight line away from the tool.
26. In a machine having a tool arranged to operate on or near the edge of a work piece, means for feeding the work piece rectilinearly an increment between successive operations of the tool, guidance mechanism including a wheel frictionally engageable with the work piece at a locality spaced from the operating path of the tool, mechanism for operating the guidance mechanism effectively only when the tool is in engagement with the work piece to serve as a center for its turning movement, and an electric curvature sensing means including a light responsive device for controlling the velocity of said wheel, and a servo motor-tachometer responsive to said device for continuously driving the wheel, said sensing means being adapted to detect change in curvature of said edge, and said device being spaced immediately ahead of the tool and close to the edge for supplying controlling power to said motor whereby the wheel velocity is continuously corrected in accordance with said curvature change.
References Cited in the file of this patent UNITED STATES PATENTS