CA1039583A - Automatic sewing machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The disclosed invention includes an automatic sewing machine having a low inertia system for translating a work holder relative to a sewing needle. The work holder is moved in a coordinate system which has been modified so that the movement of the work holder relative to the sewing needle approximates, within predefined limits, a rectilinear coordinate system. The driving power is provided by a pair of stepping motors each of whose mechanical outputs is connected by a separate cable drive to a work holder support for each coordinate system. The inertia of the work holder and the support is maintained low by separating the motors from the support.

Description

1~3gS83 This invention relates to sewing machines and in particular to a low inertia work holder control system for an automatic sewing machine.
In an automatic sewing machine, apparatus must be provided for moving a work piece relative to the sewing needle. Generally, it is the work piece that is moved. The speed at which the work piece is moved is limited by the inertia of the moving parts of the translation system. In particular, with respect to movement of the work piece, the inertia of the translation ;
system and work holder may prevent rapid acceleration and deceleration which are required to move the work piece over a distance quickly.
In prior automatic sewing machines having a work holder moving in either a linear coordinate system or a polar coordinate system, the inertia of the moving parts has prevented rapid acceleration and deceleration of the work holder. It is therefore one object of this invention to provide an automatic sewing machine with an improved work holder support and translation system which overcome the defects of known prior art devices. It is another object of this invention to provide an apparatus having a lower inertia charac~eristic and greater acceleration and deceleration characteristics than prior known devices. Further other and additional objects of the inven-tion will become apparent from the description, drawing and claims which follow hereinafter.
The invention discloses two cable systems connected to the work -holder and adapted to move the work holder in two coordinate directions. The power to move the work holder is derived from two stepping motors fixed in position with respect to the sewing needle, each of which is connected in a driving relationship to its respective cable system. The work holder is connected to an extendable arm carried on a pivoting arm. The latter pivots about a pivot point to a specified angular position controlled by the first cable system. The extendable arm moves radially over the pivoting arm and its position on that arm is controlled by the second cable system. -The invention is an automatic sewing machine for moving a movable ~395~3 element and work piece relative to a fixed location, comprising: a pivoting means for pivoting the movable element and work piece around a pivot point, an extendable arm carried by the pivoting means for translating the movable .
element and work piece radially with respect to said pivot point, first drive :
means for driving said pivoting means, second drive means for driving said extendable arm, first linkage means connecting the first drive means to the pivoting means, and second linkage means connecting said second drive means to said extendable arm for moving the movable element and work piece relative to the fixed location so that approximately a straight line is traced on the work piece whenever the movable element is pivoted about said pivot point.
Other features, objects, and advantages of.the invention will be described below in connection with the following drawings in which:
Figure 1 is a side elevation view of portions of a sewing machine :
incorporating ~he invention;
Figure 2 is a sectional top view of a portion of the sewing machine taken along line 2-2 of Figure 1 with certain parts removed; ;
Figure 3 shows one of the novel stepping motor pulleys;
Figure 4 is a pictorial drawing of the extendable portion of the arm and work holder assembly;
Figure 5 shows the extendable arm bracket for the lower clamp;
Figure 6 is a perspective view of the pivoting arm portion of the work holder assembly; ~ -Figure 7 is an exploded pictorial of the synchronizer unit;
Figure 8 is a block diagram of the electrical signal flow paths for the machine;
Figure 9 is an exploded pictorial of the homing and limit assembly;
Figure 10 is a cross sectional view of the extendable and pivoting arm assemblies taken along line 10-10 in Figure 2;
Figure 11 is a cross sectional view taken along line 11-11 in Figure 2 showing the home and limit assembly;
Figure 12 is an enlarged view of the spring loaded stripper moun- `
ted on the needle bar; and .
:.~:: -: . . - . - . .

~395~33 ~igure 13 is a block diagram of the central control logic.
Referring to Figure 1, the mechanical portion of a program con-trolled sewing machine according to the invention includes an overhanging arm 12 ~hich carries mechanical power to a sewing needle 14. The work piece to be sewn (not shown) is held generally in a work holder 16 which is moved in a hori~ontal plane by a novel power translation system. This system is driven by a pair of stepping motors 18, 20 which supply driving power to move the work holder in two coordinate directions. The power translation system acts to translate the rotary drive of the stepping motors to movement of the work holder in its two coordinate directions.
The stepping motors are driven by electrical signals from novel elec*rical circuitry. These signals are synchronized to the movement of the needle 14 into and out of the work piece by a novel electromechanical synchronization unit 22. Unit 22 is connected to and driven by a con-ven~ional hand wheel 24 of the sewing machine and supplies synchroni~ation signals to the electrical circuitry.
In this particular embodiment, the work holder is moved in a pre-determined pattern relative to the movement of the sewing machine needle.
A se~uence of instructions describing the desired pattern of movement and ~`
stitching of the work holder 16 is stored in a storage element having a plurality of randomly addressable storage locations. PreferablyJ the storage element is a programmable read only memory. In such devices the instructions stored in the various storage locations may be changed to describe a desired new pattern of movement. The storage element may also be, for example, a randomly addressable read only memory in which the stored instructions may not be changed to describe a new pattern of move-ment. Solid state memory elements of both types are available and are preferred.
Electrical control circuitry is provided which reads information 3~ from as many of the addressable locations of the storage element as , . : , .
.,, , -~039583 necessary to o~tain a complete instruction for each movement of the work holder. It also converts each instruction into a sequence of pulses to be applied to the stepping motors, and thus drives the motors at a time when, as indica~ed by the synchronizing w~it 22, the needle 14 is not engaged in the work piece. In this way, movement of the work holder is timed not to a~ersely affect the movement of the sewing needle 14.
Referring to Figure 2, the power translating system used to trans-- .-,lit power f~om stepping motors 18, 20 to the work holder 16 comprises two cable systems, one for each coordinate direction. The cable systems are arranged as follows. Pulleys 26, 28 are attached to shafts 30, 32 of stepping motors 18, 20. Cables 34, 36 are secured around pulleys 26, 28 ~espectively by screws 38, 40 respectively. In this manner, the rotational movement of the stepping motor shafts 30, 32 is converted into linear move-ment of the cables 34, 36.
; Referring now to Figure 3, each of pulleys 26, 28 has a groove 42 in which a cutout 44 is formed. The cutout extends a distance circumferen-tially on the core 42 of the pulley between lts ends so that at least part of a turn of the cable is made above the cutout 44 and part of a turn of the cable is made below it. Between these turns, the cable drops into the cutout 44 where it is secured, for example, in pulley 26 by a screw 38.
In this way, the approp-iate cable is rigidly secured to each pulley.
At one end, cable 36, which pivots the work holder about the pivot pin 68 ~see figure 10), is attached to a base plate 46 of the sewing machine by a hook and shoulder screw 48. The cable is then threaded around a free turning pulley 50 attached to the underside of a pivoting arm 52 (see also Figure 6). The cable is then threaded around a free turning pulley 53 also attached to the base plate 46, from which the cable makes a complete turn around a large pulley 54 secured to a homing and limit assembly 55.
The cable is then threaded around puIley 28 of stepping motor 20, as pre-viously described, and then around a free turning pulley 56 attached ~o the ~395~3 underside of the ~ivoting arm 52. The end of the cable is then secured to a tension assembly 58 which includes a comprcssion spring 60, one end of -the spring bearing against a support 62 secured to the base 46 and the other end of the spring bearing against a draw bar assembly 64 to which the cable 36 is secured. The draw bar assembly has a nut 66 which to-gether with the spring 60 regulates the tension on cable 36 to insure that no part of the cable becomes slack.
In operation, as stepping motor 20 rotates pulley 28 the cable 36 pulls one of the pulleys 50, 56, depending on the direction of cable mo~ement away from a center line between the needle and the pivot pin 68 and thus rotates the arm 52 about the pin 68 to one side or the : other of the clamp's center position shown in Figure 2. Pivoting arm 52 carries with it, as it pivots, an extendable arm 70 (Figures 4 and 10), to one end of which is affixed the work holder 16. Thus, as arm 52 rotates about pivot pin 68, so do arm 70 and work holder 16.
Affixed to a post 72 at the opposite end of the arm 70 from the work holder is one end of the cable 34 which controls the radial movement of the aTm 70 ~see Figures 2 and lO). From there, the cable is threaded around a free turning pulley 74~ attached to base plate 46 by means of a shoulder screw 76, and then around a free turning pulley 78 which is attached to the base plate 46 by means of a shoulder screw 80. The cable is next threaded around a free turning pulley 82 of a cable ten-sioning pulley assembly 84, also mounted on the plate 46, from which it is trained a~ound pulley 26 for 2-1/4 turns. The cable is secured to the pulley 26 by a screw 38 as previously described. Cable 34 is then threaded completely around a large pulley 86 attached to a homing and limit assembly 88. From there, the cable then extends around a free turning pulley 90 attached to the base plate 46 by a shoulder screw 92. The cable terminates at the underside of the extendable arm 70 at a connecting point 94 mounted at a point on the underside of the arm 70 which lies on a line between the : - -. ' . 1 . :
. . . , , - : i :

~3951~
pivot pin 68 ancl the scwing needle 14 when the pivoting arm 52 is in its center position. Pulley 90 has a circumferential groove (not shown~ for the cablc 34.
Cable 34 is maintained ~mder continuous tension by the cable tensioning pulley assembly 84. This assembly consists of a compression spring 96, a support 98, a draw bar 100, and a nut 102. Instead of the hoo~ of assembly 58, the reaction forcP which tensions cable 34 is trans-mitted from the draw bar to the cable through a pulley block 104 and pulley ~2. In this particular embodiment, pulley assembly 84 is advan-tageously placed, as shown, physically separated from arms 52, 70, first, because this arrangement decreases the weight of pivoting arm 52 and ex~endable arm 70, thereby reducing their inertia, and second because, as shown, assembly 84 is more accessible for maintenance and adjustment.
- In operation, when stepping motor 18 turns, the rotational motion of the motor is translated into linear cable motion and this in turn moves the extendable arm 70 carrying the work holder 16 radially with respect to the pivot pin 68.
Though, at first glance, the coordinate sys~em in which the work holder moves appears to be polar, that is, a coordinate system having a radial component delivered by moving the extendable arm 70 over the pivoting ar~ 52, and an angular component, delivered by rotating the pivoting arm 52 about pivot pin 68~ there is built into the system means for causing the work holder to move in what closely approximates a rec-tangular coordinate system with respect to the needle 14.
This means includes apparatus whereby, when the work holder is rotated about pivot pin 63, the circular line of stitching which would normally result from such movement is modified to approximate a straight line of stitching such as would be created in a rectangular coordinate system. This approximation of a straight line of stitching is accomplished automatically by shortening the effective length of the extendable arm 70 1~39S83 h- alnounts dependent on tilC amount of rotational movement imparted to the ~or~ holder by the piVOtillg arm 52. Tile amount by which the effective length of the e.Ytendable arm is shortened for a particular angular posltion of arm 52 is determined by (1) the distance from tlle connecting point 94 to both the needle 14 and the pivot pin 68, (2) the dis.ance from the axis about which pulley 90 rotates to the connecting point 94 and ~3~ the radius of the pulley 90 at the inside of the cir-ct~ferenLial gToove. Pulley 90 is spaced to one side of a line between the piYot pin 68 and needle 14J a distance equal to the radius of the pulley plus one-half the thickness of the cable.
With the structure shot~n in the drawings, connecting point 94, for a fixed position of stepping motor 18 traces a path called the in-volute of a circle (the circle being the inner circumference of pulle~- 90), and the result is to pull the connecting point 94 radially inward more and more as the angle through which the arm 52 is rotated increases from its center position. As already discussed, the amount of radially inward movement required is such as to have the needle sew along a path which approximates a straight line when only a rotational movement is imparted to the work holder by the cable 36.
This is accomplished in this particular embodiment by making the di~ance between the pivot pin 68 and a tangent point 106 between the cable 34 and the pulley 90, 3.470 inches, by making the distance between tangent point 106 and cable connection point 94, 1.623 inches, and by making the distance between the pivot pin 68 and the needle 9.000 inches.
These dimensions can be scaled up or down in larger or smaller equipment as long as the relationship between them remains the same.
As pivoting arm 52 pivots about pin 68 from its center position, the cable 34 winds or unwinds about the pulley 90, for clockwise or counterclockwise rotation, respectively. As a result, for the same angular rotation of arm 52 from the center position, the compensatory effect will . ~ ~.: - -: . . : . .

vary depending ~IpOII the direct ~oP of rotation from the center position.
In order to maintain the compensation as symmetrical as possible~ it is necessary to keep the radius of pulley 90 as small as possible, consistent itl~ proper handling o:E the cable 34. Accordingly, in the preferred embodiment of the invention, the radius for this pulley is about .328 inches.
~ n this particular embodiment, there are two homing assemblies and two limit assemblies~ olle of each being combined to operate from the same rotating shaft. As heretofore referred to these are homing and limit assemblies 55 and 88. Both homing and limit assemblies 55, 88 perform the same two functions. One is to position the work clamp at a predetermined location ~"home") and the other is to provide an indication, in this particular embodiment a contact closure, that the work holder is being moved beyond the predetermined allowed limits. Both limit assemblies also provide firm physical resistance to movement beyond the predetermined allowed limits. The homing assembly is intended to prevent cumulative errors in reference position from occurring from cycle to cycle and to always maintain registration. An additional function of the homing assembly is to insure extremely accurate start or end point positioning to enable auxiliary devices, such as slitting knives to cut buttonholes, ~ -to he actuated and to perform repeatedly with a high degree of positional accuracy.
Referring to Figure 11, only homing and limit assembly 88 for limiting travel and effecting homing of arm 70 in the radial direction will he described in detail, assembly 55 having a similar operation and construc-tion ~or the rotational coordinate direction. Pulley 86 of the homing and limit assembly 88 has a sufficiently large diameter that the maximum allowable cable travel for moving the work holder in a radial direction results in less than a complete revolution of the pulley. By thus limiting the angular rotation of a shaft 108 on which the pulley 86 is mounted to .
-. - . . . -. . :
: - . .. ~: . . .

11~395~3 less tllall a full revolution, adjustable limit switches, secured in an operative rcl~tion -to shaft 108, allol~ full range of radial movement of the ~ork holder while providing a contact closure to electrical control circuitry to indicate that the work holder is being moved beyond the ; present limits.
Referring to Figures 9 and 11, the limit assembly portion of homing and limit assembly 88 includes a sleeve 110, with bearings 112 and ll~ pressed into its ends. The sleeve is held in a support assembly 116 by means of a screw 11~. Limit switch brackets 120 and 122 fit around sleeve llO and are held in position by clamps 124, 126 against a disc 128 of the suppoTt assembly 116 with screws 130, 132 respectively. Limit switch assemblies 134, 136 are held on brackets 120, 122 respectively by means of screws 138. A trigger 140 for the homing and limit assembly, but used only for the limit function 88 is secured to the underside of pulley 86 by means of screws 142. Pulley 86 mates with and is rotatable ;
on shaft 108 above disc 128 of the support assembly 116. Trigger 140 moves in an arc between limit switch assemblies 134 and 136 as pulley 86 rotates in response to movement of cable 34.
In normal operation, the work holder does not travel beyond the ~redetermined allowed limits because the instruction sequence controlling move~ent of the work holder does not instruct the drive circuitry to ~ove the wor~ holder that far. However, if for any reason the stepping motors continue to drive the work holder beyond the allowed range of move-ment and therefore into potential contact with the sewing machine needle, possibly damaging the needle or the work holder, trigger 140 engages the con~acts 154 or 156 of limit switch assembly 134 or 136 causing them to close. Closure of normally open contacts 154 or 156 signals the electrical control circuitry to prevent further stepping of the corresponding stepping motor until the direction of travel for that motor is reversed.
As an extra safety, should the limit switches, the wiring to them, 10395~3 or related electrical circuit Eail so that the motor continues to be cIrivell f~lrther out o~ the allowed limits, trigger 140 urges contacts 154, 156 against one of the backup screws 158 whicil have a fixed position with rcspect to support assembly 116. This prevents further movement of the trigger 1~0, and therefore of pulley 86, cable 34, and stepping motor 18.
Further movement of the extendable arm 70 is thereby prevented and damage to the sewing needle 14 or the wor~ holder is avoided. Backup screws 158 are preferably adjusted to stop contacts 154, 156 one motor step after the contacts have actuated. Similar apparatus is used for limiting travel o~ the work holder in the other coordinate direction.
The homing assembly portion of the homing and limit assembly 88 positions the work holder,upon command, to a predetermined location, the location being anywhere within the working range of the two-coordinate system. Because of the nature of the coordinate system in this embodiment, it is preferable to have the home position at the center of polar travel and near that limi~ of radial travel at which the extendable arm is mos~
extended.
The apparatus for sensing the home position is located at the lower portion of the homing and limit assemblies, and includes apparatus -~
having indicating portions driven by the cable 34 via the pulley 86 and shaft 108 whose motion is thus synchronized to the movement of the cor-responding cables driving the work holder. Only the homing assembly por-tion of the homing and limit assembly 88 will be described in detail, the ho~ing assembly portion of homing and limit assembly 55 being substantially the same in operation and structure.
The homing assembly includes a notched homing disc 160 and an optical sensor 162 arranged so that the sensor detects the presence or absence of the notch. In this particular embodiment, the optical sensor 162 is a light-emitting diode and an interrupter type phototransistor mounted as one unit which is supported on a bracket 164 by screws 166.

-: :

1~395~3 Brac~et 16~ is secured to the lower section o~ support assembly 116. The homing disc 160 is secured to the lower end o~ shaft 108, and rotates in union with pulley 86 wilich is coupled to the upper end of shaft 108 by means of pin 146, lever 14~1, adjusting screw 150 and bracket 148 affixed to pulley 86. Turning the adjusting screw lS0 rotates homing disc 160 with respec~
to the cable 3~ and the work piece of that easy and precise adjustment of the home position is possible.
In operation, an output signal from the optical sensor 162 deter- ~ ;
mines the direction in which stepping motor 18 must be rotated to move edge 10 168 of homing disc 160 into alignment with the sensor. As soon as the edge reaches alignment, it causes a signal output change and the motor to stop.
If the motor overshoots proper alignment, the motor can be reversed by the electrical control circuitry and the disc brought into more precise alignment with its aligned position. A similar apparatus is used for the other co-ordinate direction.
Referring nol~ to Figure 6, pivoting arm 52 is provided with free tu m ing rollers 170, 172, attached to pivoting arm 52 by means of screws 174, and free turning rollers 176, 178 attached to levers 180, 182 res-pectively by means of screws 184. Levers 180, 182 are attached to pivoting 20 arm 52 by screws 186 about which they can freely pivot. A compression spring 188 its hetween levers 180, 182 and is held in place by lugs 190, 192 on levers 1~0, 182 respectively. This construction makes rollers 176, 178 movable and spring loaded. The extendable arm 70 rides on rollers 170, 172, 176, 178 as will be further described below.
Extendable arm 70 (Figure 4) rides on tracks formed by triangular shaped portions 194, which allow the arm to ride on rollers 170, 172, 176, 178. Affixed on the underside of extendable arm 70 is a bracket 196 (Figures 4 and 5) to which a lower clamp jaw 198 of the work holder is attached by means of two screws 200. An upper clamp member 202 is pivotally mounted about its 30 rear end around an axle 204. Upper clamp member 202 is urged downwardly _ .

11~39S~3 about the a~le by a compression spring 206 that fits around a stud por-tion 203 of thc bracket 196. A tlnmlbscre~ 21Q is used to adjust the spring force.
Assembled, the fo-~ard part of extendable arm 70, the part nearest the work holder, rides on rollers 170, 176 while the trailing pa~t of the arm 70 rides on Tollers 172, 17S. The work holder, attached to the exten-dable arm 70, pivots with pivoting arm 52 around pivot pin 68 by means of an opening in pivoting arm 5% through which pin 68 extends~ As previously des-cribed, pivotal ~vement is controlled by cable 36, driven by stepping motor 20. Extendable arm 70 riding on the rollers 170, 1729 176, 178 ln tracks 194 moves along the pivoting arm in a substantially radial direction with respect to pîvot pin 68. As previously described, cable 34, driven by stepping motor 18, controls the radial movement of the extendable arm 70.
Th~s, depending on the direction of motor rotation, one end of the cable at stud 72 pulls while the other end of the cable at connecting point 94 relaxes, or Yice versa. In this way, there is always a positive drive to control radial movement of the extendable arm.
Upper cla~p 202, as noted above~ is urged downward by spring 206.
In this way, the work piece is clamped and held in position between upper and lower clamp jaws 220, 198. At the beginning of a sewing cycle when the 2Q ~ork piece is placed in the work holder, and at the end of the sewing cycle when the wor~ piece is removed from the work holder, the clamp 202 must be raised. Referring to Figure 1, the apparatus for raising the upper clamp includes a solenoid actuated air valve 214 which, in response to a signal from the electrical circuitry at an appropriate time in a sequence of ins~ruc-tions, is energized and thereby admits air under pressure to a cylinder 216.
In response, cylinder 216 pulls on cable 218 to lift clamp 202. At the beginning of a cycle, after the operator has placed the work piece in the work holder, the clamp will, in response to a manual or pedal switch, close as solenoid valve 214 is de-energized causing cylinder 216 to extend its 3Q piston by means of an internal spring ~not shown) and relax the cable 218.

._ ..

1~)395~3 Spring 206 thercby ~Irges upper clamp 202 to pivot about axlc 204 to forcibly engage the ~ork piece bet~een lo~Yer clamp ja~Y 1~8 and upper clall~p jaw 220.
As a safety precaution, a clamp closed sensor 296 is provided to prevent automatic machine operation until the clamp has completely closed.
Closure of the upper clamp is sensed by cable tension sensing assembly 222 ~Figure 1). l~en the clamp is fully closed, thc cable relaxes and in res-ponse thereto a switch (not sho~Yn) in the assembly 222 resets by its own internal spring.
For proper operation of the apparatus, the movement of the work holder must be synchroni~ed to the stitching cycle so that the work holder is moYed only when the needle is not in the work piece. Furthermore, the sewing machine must stop at the end of a sewing cycle with the needle in the up position so that the work holder may be moved to the home position and so that the work piece may be removed from the work holder after the upper clamp is raised. Thread cutting is also done as part of this "needle-up"
sequence. These functions are performed by a commercial apparatus, Quick, Model No. 800-ST-362 (not shown), which is modified somewhat for this par-ticular application.
Referring to Figure 7, the electromechanical synchroni~ation unit 22 includes a rotating slip ring assembly 224 which is affixed to the sewing machine hand ~qheel 24 by means of an adapter 226. A stationary portion 228 of assembly 224 inciudes electrical brushes 230, 232, 234, 236 affixed to a brac~et ~not shown). Insulating portions 238, 240 and 242 provide electrical interruptions in three slip rings 244, 246 and 248 when these portions are contacted by brushes 230, 232, 236 respectively. Brush 234 is used to supply electrical current to the slip rihgs. Current from the three active slip rings is used in a conventional manner to activate a commercial "needle positioner" (Quick, ~lodel No. 800-ST-362 mentioned above). A pulley 252 and a belt 254 (Figure l) connect to a pulley ~not shown) on the sewing machine needle positioner. By means of suitable gearing in the needle positioner and .
- :: - . . . ' .~ . , .

i~3gs83 in responsc to electrical inpllts from the elcctromechanical synchroni~ation unit ?? and from thc electrical control circuitry, the ncedlc positioner ~ill cause the sewing ~naclline: ~a) to run at fast speed or slol~ speed; (b) to act~late a solenoid powered thread cutter (not shown) and a thread tension release solenoid (not shown); and (c) to stop the machine with the needle up.
This apparatus is all commercially available and it is mentioned here only for the purpose of adequately describing certain additions which follow.
The synchronizer 22 includes a photo-reflective transducer 256, its holder 25S, a mounting strap 260, a photocell commutator ring 262, a a set screw 264 retaining ring 262 at any chosen angular position on the assem~ly 224, a cover 266, and a scale 268 either imprinted on the cover or separately printed and affixed by adhesive. In operation, light emitted by transducer 256 strikes the surface of ring 262 and is reflected to an optical sensing portion of transducer 256 creating an output current. The output current remains constant except at a notched portion 270 of ring 262 at which the amount of reflected light and therefore the output current are greatlr diminished. The notched portion and the corresponding signal change initiate the beginning of a time period in which the work holder can be moved without damaging the needle, that is, the beginning of the time period immediately after the needle has been withdrawn from the work piece. The needle positioner, although commercially designed for actuation by treadle, is made fully automatic by attaching an air cylinder (not shown) to its actuating lever. The air cylinder is controlled through an electric air yalve (not sholm) by current from the electrical control circuitry.
Referring to Figure 12~ the presser foot of the sewing machine has been replaced b~ a spring loaded stripper mounted on a needle bar con-sisting of a stripper 272 and a compression spring 274. One end of the spring is affixed to the lower end of the needle bar and the other end is affixed to the top side of the stripper 272. ~le stripper holds the material down against the throat plate to allow a needle thread loop to form as the needle ~:)395~3 1~1 begins to rise and to be picked up by tlle se~ing machine's rotary hook (not sho~n).
/~s noted above, the addressable storage element which is preferred in this embod-iment is a programmable read only memory (PROM). i~ith the ; proper e~uipment, the operator of an automatic sewing machine according to this invention can change or add programs (i.e., instructions or a sequence of ;nstructions~ to a PROM. Depending on the information capacity of each storage location and the information content of each instruction, a single instruction may be stored in a single storage location. On the other hand, in the preferred embodiment of the invention, each instruction requires more than one storage location. The sequence of instructions stored describes a pattern which the automatic sewing machine work holder will follow. In this particular embodiment, the PROM has a randomly addressable eight binary digit ~bit~ word in each storage location and a total of 256 such locations.
Each instruction includes a command and work holder positioning data. In the preferred embodiment there are four commands. The first co~mand directs movement of the work holder without stitching; the second directs movement of the work holder while stitching slowly; the third directs movement of the work holder while stitching at a fast rate; and the fourth indicates the end of the sequence of instructions and directs movement of the work holder to its home position. Each of the first three commands recited above requires two groups of positioning data to form a complete instruction. Each data group includes directional and stepping information necessary for a different one of the two coordinate directions to determine the next position of the work holder. While there are many possible ways of providing this information, it is preferred to construct each data group as a signed number which indicates the number of steps and the direction in which the work holder is to be moved. Thus, this particualr embodiment of the invention utilizes an open loop system~ that is, the work holder is moved from place to place during a sewing operation without any feedback . . _ ,:

1'~)3958;3 to indicate its present position. In this particular embo~iment, the maximum allow~ble number of steps in each coordina~e direction is twelve per lnstruc-tion when stitching,an~ fifteen per instruction when the work holder is moved sYithout s~itching.
In this embodiment, each instruction, when written in binary requires twelve bits. The designation of the command portion of each instruction re-quires t~o bits and the work holder positioning data requires five bits for each coordinate direction, one for the direction (positive or negative) and four bits to designate the number of steps. Thus, each instruction of the sequence requires more than one addressable location`~in the PRO~I.
Once the PROM has been programmed, that is, once the PROM contains - a sequence of instructions in a predetermined order to describe a desired sewing pattern, the sewing machine is ready for operation. If the programs are sholt enough, two or more programs may be stored in a single storage element. In this case, switches, for example on the front panel of the sesYing machine, may be manually operated to choose which of the programs is to be used.
Referring to Figure 8, the operation of the sewing machine is con-trolled by a central control logic 276. First the operator places a work piece in the proper position in the work holder 16. Then, when a foot pedal 278 of the sewing machine is depressed half way by the operator, a first switch (not shown) is closed causing the central control logic 276 by means not shown to generate a signal which causes solenoid 214 to lower upper clamp 202 to engage and hold the work piece. After the clamp is lowered, the foot pedal.is fully depressed by the operator and, if the clamp 202 is fully closed, automatic operation of the machine begins. In normal operation, a "homing" cycle is first initiated. Thereafter, the first in-Struction is read from the storage element 280, here shown as a PROM, according to the program selection switches (not shown) on the front panel 282 by the central control logic 276. This logic responds by providing the - . .
. , .

~()39S~3 corrcct n~n~er of pulses for moving the l~ork holdcr and, after a signal from electromccllall;cal synchrollization unit 22, transmits these pulses to motor drive logics 28~ and 286. Drive logics 284, 286 drive rcspcctively power drivers 28S, 290 l~hich in turn drive stepping motors lS, 20 in the desired directio~ and througll the desired rotation.
e pulses to the drive logics 284, 286 are arranged to be ~ aperiodic to increase the machine cycle rate and to prevent unwanted oscilla-- tions and therefore unwanted feeding of the work piece againstthe needle.
The work piece thus mo~es in a true intermittent motion, the work piece being stationary when the needle is inserted into it. More particularly, the cen-tral con$rol logic 276 includes means for spacing the first three pulses of a series of pulses and the last two pulses of the series further apart than any remaining intermediate pulses. Where the number of pulses to a stepping motor is less *han three, the amount of current from the power drivers 288, 290 is reduced (by known means not shown) to further minimize oscillatiolls in the stepping motors, The next instruction is then read and carried out, ;~
followed by *he one after that, etc., until the last instruction has been imple~ented. In response to the last instruction which will be a stop command, the central control logic causes the needle positioner to halt the sewing machine, causes the thread to be cut, and then initiates a second "homing" -cycle.
The 1'homing" cycle is controlled by the central control logic whichJ in response to the signals from optical sensors 162, 294, cycles the stepping motors to return the work holder to its radial and rotational "home"
location.
Other inputs to the central logic are from the limit switch assemblies 134, 136, of both coordinate directions, clamp sensor 296 of clamp tension sensing assembly 222,and cutter circuitry 297. Cutter circuitry 297 signals the control logic after the thread has been cut. There is also included a needle/thread break sensor 298 which signals the control logic ., .

1~39583 276 of a break ;n tllc n~ecllc tllrcad. Upon reccipt of a ~rcak signal ~rom a sensor 2~S> thc control logic 276 causes tlle necdlc positioner to halt the se~ g machine cmd inlli~its any furtller movcment of the work holder by stop-ping the incrementation of an address counter 372 (F:igure 13) which sequential-ly ad~resses the storage element. Thus, the address in address counter 372 is preserved and t1le control logic 276 waits for a restart signal from the ~Iont panel before starting up again. As will be explained hereafter, once the thread or needie has been repaired and replaced, the operator may restart the machine at the beginning of the sewing pattern or restart it at the instruction follo~ing the instruction at which the break occurred.
Depending upon whether an instruction requires slow or fast stitch-ing~ the control logic 276, in response to that instruction, will signal, through driver 300, a control box 306 of a "Quick" needle positioner (not sho~n) to cause machine to stitch at the required speed. If a stop command is read, control logic 276, in response to that instruction, deactuates through driver 30~, brake clutch valve solenoid 308 in the needle positioner to stop the sewing machine, Referring to Figure 13, the control logic 276 ~Figure 8) is shown in greater de*ail. A sequencing circuitry 322 monitors over the cable labelled "CHEC~S": {a) inputs from synchronization unit 22; (b) clamp sensor 296; (c) needle/thread break sensor 298; ~d) cutter circuitry 297; (e) limit switch assemblies 134, 136, (f) front panel 282; and ~g) optical sensors 162, 294 for both coordinate directions. Signals from foot treadle 278 are read over the line labeled "STA~T". Gating logic circuits provided within the sequencing circuitry ser~e to halt machine and work holder operation if the proper operating conditions are not maintained. When the operator fully depresses the treadle~ this causes an enabling signal on line 324 to appear and initiate the first "homing" cycle when the clamp sensor indicates the work holder is closed. This homing insures that the work holder will be at a predetermined ini~ial position at the beginning of a sewing sequence.

.. " , ~ .

1~39583 lloming circuitry 326 operates together with homing and limit assem~l;es 55, 88 to preset thc work holder at the desired locations for sew-in~ in each of the tl~O coordinate directions. For convenience, the coordinate directions will be called X and Y, corresponding to a rectilinear coordinate system, although in the preferred embodiment the coordinate system is based on polar coordinates modified to approximate a rectilinear system. The homing circuitry, in response to the enabling signal over line 324 from the sequenc-ing circuitry 322, provides output signals over lines 332 and 334 to a direc-tion steering circuitry 336, based upon the inputs from optical sensor 162, 29~ over lines 328, 330. These output signals indicate the direction in which the stepping motors should be moved. Direction steering circuitry 336 gates t~e si~nals on lines 332, 334 to the motor drive logics 284, 286 to control the direction of movement of the motors 18, 20. These signals are also gated to a limit circuitry 342 over lines 338 and 340 whose operation will be described below. The homing circuitry 326 also enables a pulse modifier circll~try 344 by a signal over line 345 so it is in condition to be enabled to provide output electrical puises over lines 346 and 348 from the low speed oscillator 368. After the first homing approach, this output is preferably reduced in frequency by a rate modifier circuitry 349 to motor drive logics 284, 286, as will be explained hereinafter, by the signals over a command line 351 from homing circuitry 326.
Pulse modifier circuitry 344 is enabled to gate these pulses to the motor dri~e logic by signals from a run/sew circuitry 350 over lines 352 and 354. Signals on one of these lines control the gating of pulses to one of the motors 18, 20 while signals on ~he others control the gating of pulses ~o *he other motor. The signals on lines 352, 354 are provided by the run/sew circuitry 350 in the homing mode by a set of input signals over lines 356 and -358 from homing circuitry 326 when there exists an enabling signal over line 324 from the sequencing circuitry 322. The absence of signals over one of lines 356, 358 and thus one of lines 352, 354 causes the pulse modifier cir-:~1)3~583 cuitry to inllib;t pulsillg to tlle corrcsponding stcpI)ing motor. ~I:is occurs ~hellever tllc home position for thc correspondi]lg coordinate direction has been achicved. For propcr opera-tio7l of tile pulse modifier circuitry during the homing cycle, tllere must be enabling signals over line 3~5 and one or both of lines ~52, 35~.
In all cases, the stepying motors overshoot the home position.
IYhen this occurs the optical sensors generate a signal l~hich causes the motor involved to reverse and "zero in" on the correct home position. This is done by changing the signals over lines 332 and/or 334 according to information from the optical sensors to reverse the direction of one or both stepping motors. The homing circuitry also includes additional logic circuitry for ensuring that the final approach of each motor to its home position is always from the same direction irrespective of the initial position of the work holder prior to homing. In addition, all homing motion after the first home approach is accomplished at a reduced rate generated by rate modifier circuitry 349. I~leans in the homing circuitry 326, responsive to the optical sensor outputs, provide the signal over command line 351 for causing the stepping rate to be reduced. This mixture of stepping rates creates an optimally fast homing cycle.
In this particular embodiment there is always at least one change of direction of approach to the "home" position for each motor. If, after reversing the motor, t~e second approach direction is not the same as an approach direction predetermined in advance, the direction of motor rotation is automatically reversed again by logic in the homing circuitry which senses the direction of approach and a third and final approach is made from the predetermined approach direction. In this way, greater accuracy in position-ing the work holder is achieved.
I~hen the first homing cycle has been completed a signal is placed by the homing circuitry on line 360 from the homing circuitry 326 to the sequencing circuitry 322. In response to this signal, the enable level on ' ' '' " ,:' ' ' .' "

~395E~3 line 32~ is immediately rcmo~e~l by thc scqucnclng circuitry thereby preventing further movemellt of the wor~ llol~er. '~le scquenc;ng circuitry thell initiates a memory c~cle ~y gcnerating an enal)le signal level over a line 362. This signal level allo~s ~ords from storage element 2S0 to be addressed and read as follolYs. The output of a high speed oscillator 366 is red~lced by a counter -- heYe la~eled low speed oscillator 368 l~hose output is one-tenth the frequency o~ the high speed oscillator. The low speed oscillator 368 provides periodic pulses Yhich determine the rate at which the stepping motors will be driven.
The enable signal on line 362 enables the address counter 372 whose output on lines 374 represents the address of the word which is going to be read from the storage element. The enable signal on line 362 also enables a count to three counter 376 whose outputs determine which of three units portions of a ~ord of storage are read into. The three units comprise a storage unit 378 which receives the command portion of the instruction and the signs of the coordinate directions, upcounter 380 and upcounter 382. These two upcounters respectively receive the work holder positioning data for each coordinate direction in inverted form after it is inverted by an inverter 384 comprising several inverting gates.
In operationJ the first clock pulse output of the high speed oscillator 366, after line 362 is enabled increments address counter 372 resulting in a new four bit word being available from the storage element over ~ .
lines 390. The same clock pulse also increments the count to three counter which causes an enabling signal to appear on one of its output lines, namely line 392 corresponding to a count of one. This in turn enables the upcounter 382 to store the four bit word in inverted form. The inverted four bit word is entered into the upcounter 382 by the trailing edge of the same first clock pulse over line 393.
In the same fashion, the next clock pulse from the high speed oscillator ~corresponding to a count of two) increments counters 372 and 376 and causes the inverse of the next addressed four bit word to be read into :. : . . - . .
. ~- . : ,. . - . , ,~

~:)39583 upcollntcr 3S0 as detcr11)ined by ~n e1l~bling signal froJn count to tllrce countcr over l:inc 39~ his corresponds to a col1nt of two.
T11e tllir~ clock pulse from the high speed oscillator again in-crements counters s7~ and 376 and causes the next addressed four bit word to be read into stora~e Imit 37~ as ~etermine~ by an enabling signal fro1n the count to three co~mter over l;ne 396. This corresponds to a count of three.
~he enaoling signal on line 396 is also provided by a connection, not shown, to the sequencing circ~litry 322 in response to which the enabling signal on line 3~2 is removed. As a result, the count to three counter 376 is reset to ~ero~ and address counter 372 cannot be incremented. By this time, one com-ple*e instruction has been read from the memory and is stored, parts in each of upcounters 3S0, 3g2 and storage unit 378.
All *hat remains to utilize this instruction is to translate it - into ~ovement of the stepping motors 18, 20 and into motion of the sewing machine, if required. Where the previous instruction required a sewing opera-~ tion, this is accomplished by a signal from the synchronizing unit 22 which is ; connect~d to the sequencing circuitry over one of the lines entitled "C1~CKS"
and s~hich causes the sequencing circuitry to provide an enabling signal over - line 397 indicating that the needle is clear of the work piece. Where the pre~ious instruction did not require stitching, for example when the work holder is positioned for sewing following the first homing operation, the e~uivalent of the needle disengage signal is generated internally by logic means within the sequencing circuitry to produce an enabling signal over line 397 a short time after the new instruction is read into storage. In either instance, the ena~ling signal over line 397 is connected to the pulse modifier ciroultry 3~ which allows the stepping motors to be driven in accordance with the o~tputs of upcounters 3S0, 380, 3~2 whenever appropriate signals are present on lines 352, 354, 442, 444. The latter two lines (from limit cir-cuitry 3~2~ will always have appropriate signals on them for this purpose unlessthe work holder is outside of its permitted range of movement.

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:- ~ - .

~395~3 A~`ter t11e er1a~ 1g signal is proYided on line 397, clock signals ~rom tllc lo~ speccl oscillator increment upeountcrs 380, 382 through a count enable circuitry ~100 ov~r lines ~02, ~10~ t the same time, the same clock signals ~rom the lo1~ speed oscillator are connected to pulse modifier circuitry- 3~4 PuIse trains from the pulse modifier circuitry to drive each stepping motor are derived from these lol~ speed clock signals ~rom each coordinate direction.
The outputs of upcounters 380, 382 determine the number of output pulses there will be to step each motor in a given coordinate direction. The directions are determined by the direction indicating portions of the word stored in storage unit 378. The direction indicating portions are gated to - the stepping motor drive logic and the limit circuitry by direction steering logic 336. The number of output pulses to each motor corresponds to the data, the inverse of which was initially stored in the upcounters. The upcounters are constructed so that, when they have been incremented-a number of times equal to the number of steps specified in the instruction, a carry output appears on lines 406, 408. The carry outputs are sent to the run/sew circuitry ~
and affect the pulse modifier circuitry 344 by run/se~ circuitry 350 response ~ ;
over lines 352, 354. As noted above, signals over one or the other of lines ~ -352, 354 indicate that a proper number of input pulses from the low speed oscillator have been received for a particular coordinate direction. When both carry outputs appear (andJ of course, they need not appear in ~he same clock cycle) the sequencing circuitry 322 causes the enable signal on line 397 to be lemoved thereby indicating that the information contained in the instruction last read from the memory has been utili~ed.
As long as the wor~ holder is within the limits that are mechani- ;
cally set in the limit portion of the homing and limit assemblies, the pulse modifier circuitry operates as follows. During the homing cycle when there is the enabling signal on line 3~5, pulses from the low speed oscillator are applied to the stepping motors in the coordinate direction or directions in-. .

-~.: , : :. - . , .. :-. ~ -: , ~395~3 dicated by tlle si~n~l5 on lines 332, 334. Ihe output pulse trains are p~r;odic. During that portion of the logic operatioll wilen there is an cnabl-ing signal o~ line 397 due to a single instruction being utilized, the periodic pulses from the low speed oscillator 368 are gated according to the data stored in the upcounters 380, 382 to provide pulse tr~ins to the stepping motor drive logics over lines 346, 34~. If the number of steps in a coordin-ate direction is at least three, the pulse train for that direction is derived as follows.
After the enable signal on line 397 appears, the first clock signal from the low speed oscillator is passed through the pulse speed oscil-lato~ is passed through the pulse modifier circuitry to the drive logic. The second an~ third clock signals from the low speed oscillator are blocked and an initial delayed pulse is added by the pulse modifier circuitry approximately equidistant between what would originally have been the second and third clock signals. The clock signals from the low speed oscillator after the third clock signal pass through circuitry 344 essentially unchanged as long as there is no change in signal level over whichever one of lines 352 or 354 cor-responds to the coordinate direction concerned. After a change in signal level on one of lines 352, 354 further clock signals from the low speed oscillator are blocked from forming part of the output pulse train for that coordinate direction. Thereafter an additional terminal delayed pulse is automatically added by the pulse modifier to the otherwise terminated output pulse train.
This pulse is added a predetermined interval of time following the las~ pulse in`the train,;the time interval being greater than the time beh~een pulses from the low speed oscillator. As a result, the drive pulses to the stepping motors are aperiodic, having a somewhat lower frequency at both the beginning and end of the pulse train and a higher frequency in the middle of the pulse train. This allows an increased machine cycle rate with smaller oscillations and therefore more accurate positioning.
~hen the information from storage element 280 was entered into up-.. . .. ..
. .

1~39583 counters 3sa and 382, if thc number of stel)s specified for either coordinate dircction was onc or t~io, this information was stored in decode circuitry 398 and is immediately made available to the pulse modificr circuitry over lines .lO9. Tlle pulse modifier circuitry in response to this information from decode circuit~y 39S alters its normal operation, described above, so that, if only two stepping pulses ~re required, onl~ the initial delayed pulse is added and if only one pulse is required neither the initial nor the terminal delayed pulses are added.
~en the called for number of X and Y steps has ~een obtained, as 1~ indicated by a change in the carry signals from thè upcounters, the enable signal 397 is removed and the sequencing circuitry, after a short delay starts a new ~cmory cycle and provides an enable signal over line 362 to read the next instruction from memory. The operation of control circuitry 276 then repeats until an end of program signal is encountered. ` ~;
The limit circuitry 342 discussed briefly above operates so that, if the limit switches indicate that the work holder has reached a boundary, a signal from li~it circuitry 342 to pulse modifier circuitry 344 over one of lines 442, 444, depending upon the coordinate direction involved, acts to in-hibit further drive pulses to the corresponding stepping motor until the direction of stepping has been reversed, as indicated by the signals over lines 338 or 340 from direction steering circuitry 336. The only effect this has on the operation of the sewing machine or the electrical control circuitry is to halt movement of the work holder in the coordinate direction concerned.
The central control logic and the sewing machine continue to operate mormally except for inhibiting drive pulses to the stepping motor concerned.
Storage element 378 stores a command and direction information as described above. Each bit of the command is connected to decode circuitry 430. Each output line of decode circuitry 430 collectively labeled 432 is associated with a particular command. The decode circuitry decodes the command stored in unit 378 and provides an enabling signal level on the one of its 1~39583 output lines ~l32 associated l~ith that col~nancl. Output lines 432 are connccted to the se~ucncing circuitry 322 wl~re thcy are amplified before bcing sent on to thc "Quic~" unit 306 ovcr line ~67 -to control thc operation of the sewing machine .
The sequencing circuitry utilizes the signals over lines ~32 for *~o purposes~ First to differentiate between st;tch and no stitch commands to effect proper operation of the needle positioner and second, in response to a "stop" command, to provide end of program sequencing which includes signal-ling cutter circuitry 297 to cut the thread and return the work holder to its "home" position. To accomplish the latter operation, an enabling signal on a-line 32~ is generated in response to an "end of cuti' signal from the cutter circuitry 297 in the presence of an "end of program" signal or command over one of the lines 432. After this second homing cycle is completed, the upper clamp is raised in response to a signal from central control logic 276 to a solenoid actuated air valve 214 through driver 302 so that the work piece can be remo~ed.
The Quick unit 306 utilizes the signals over lines 467 from the ., .
sequencing circuitry 322 to stitch fast or slow and to initiate a needle up and trim in response to the stop command.
In the particular embodiment shown in Figure 13, storage element 280 is a PROI~. In many circumstances the program describing a pattern will not occupy all of the memory and in fact may not occupy even half of the memory.As a result, the PROM is split into two portions, an odd and an even portion and switches on the front panel determine whether the PROM is used in its split mode (odd or even) or in a full complement mode. In the preferred em-bodiment, each location in the PROM contains eight bits as mentioned above.
These bits may be numbered for convenience 1, 2, 3, ..., 8. The odd half of the memory is defined here as the bits of each word numbered 1, 3, 5, 7, and the even half is defiaed as the bits numbered 2, 4, 6, 8. In other embodi-30 ments of the invention there will be other acceptable divisions of the memory.

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~39S1~3 Program select circuitry 460 in ~esyonse to the ront panel switches llas an output over line ~162 wllicll indicates to the PROM whether to choose tile program store~ ;n the odd or even storage locations. When a program occupies the entire PRO~I, it is s~ritten in the PRO~i so that, by sequencing first through the instructions as if it ~Yere an "even" program and then through the instructions as though it were an "odd" program, the entire program is read.
In this case, a carry signal from address counter 372 over line 364 tells the program select circuitry s~hen to switch from "even" to "odd".
Other embodiments will occur to those skilled in the art and are within the following claims. ~ .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An automatic sewing machine for moving a movable element and work piece relative to a fixed location, comprising: a pivoting means for pivoting the movable element and work piece around a pivot point, an extendable arm carried by the pivoting means for translating the movable element and work piece radially with respect to said pivot point, first drive means for driving said pivoting means, second drive means for driving said extendable arm, first linkage means connecting the first drive means to the pivoting means, and second linkage means con-necting said second drive means to said extendable arm for moving the movable element and work piece relative to the fixed location so that approximately a straight line is traced on the work piece whenever the movable element is pivoted about said pivot point.