US3776157A

US3776157A - Flat stitch forming and cover thread laying mechanisms for sewing machines

Info

Publication number: US3776157A
Application number: US00245104A
Authority: US
Inventors: H Szostak
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1972-04-18
Filing date: 1972-04-18
Publication date: 1973-12-04
Anticipated expiration: 1990-12-04
Also published as: IT980007B; JPS4921252A; GB1372339A; JPS5511074B2; DE2318191A1; FR2186031A5

Abstract

A compact, lightweight, high-speed machine of low-silhouette frame construction for forming flat seams such as those of stitch type 605 used, for example, for attaching elastic waistbands, borders, cuffs and collarettes to knit undergarments, athletic shirts and the like. The machine utilizes two or more needles each carrying a needle thread, to form, in cooperation with a looper, parallel rows of chain or double-lock stitches. A spreader which reciprocates in a straight line path and which cooperates with a special cover thread guide, places a cover thread in proper relation with all of the needle threads on the upper surface of the work piece. The looper is carried by an oscillating and horizontally reciprocating shaft and cooperates beneath the work piece with all of the needles to supply the looper thread for the chain stitches aforesaid. A single take-up is provided for all of the needle threads and the cover thread while a separate take-up is provided for the looper thread.

Description

Siestak Dec. 4, 1973 FLAT STITCH FORMING AND COVER THREAD LAYING MECHANISMS FOR SEWING MACHINES Primary Examiner--James R. Boler Attorney.lames D. Ock

[5 7] ABSTRACT 75 Inventor: Henryk Szostak, Oak Park, 111. compact, lightweight, high-Speed machine of silhouette frame construction for forming flat seams [73] AsslgneeZ Union speclal Machine Company such as those of stitch type 605 used, for example, for

Chlcago, Ill. attaching elastic waistbands, borders, cuffs and col- [22] Filed: Apt 18, 1972 larettes to knit undergarments, athletic shirts and the like. The machine utilizes two or more needles each PP N03 245,104 carrying a needle thread, to form, in cooperation with a looper, parallel rows of chain or double-lock 52 U.S. c1. 112 162, 112/100 Stitches A Spreader which reciprocates in a Straight 51 1m. (:1 0051 1/20 line P and'which cooperates with Special cover [58] Field 61 Search 112/262, 162, 163, thread guide, places a cover thread in P p relation 112/1 66 00 255 with all of the needle threads on the upper surface of v the work piece. The looper is carried by an oscillating [56] References Cited and horizontally reciprocating shaft and cooperates UNITED STATES PATENTS beneath the work piece with all of the needles to supply the looper thread for the chain stitches aforesaid. Moffatt A Single p is provided for of the needle 1,088,339 2/1914 Goodwin 112/100 X h d d h th d k 2,636,462 4 1953 Peterson 6118].. 112 162 t 6 cover Separate ta 1,855,254 4 1932 Moffatt 112 100 Provlded the thread- 18 Claims, 16 Drawing Figures ,1 I I W n a4 1%, Y/ K 3 -WE 44 66 H l I l [5b 1 I I 1111 {LL46 2o 36 1 I l 1' l 22 i 32 33 l I I5 l l "I PATENTED BEE 4 I973 SHEET 10F 6 PMENIED um 4 I915 SHEET 2 OF 6 PATENIEDBU: 4 I975 SHEET 3 BF 6 FLAT STITCH FORMING AND COVER THREAD LAYING MECHANISMS FOR SEWING MACHINES BRIEF DESCRIPTION OF THE INVENTION Considered first from'a broad standpoint the present invention provides as an end result a sewing machine for forming flat seams by the use of a plurality of needles, a looper supplying a looper thread for interlocking with needle-carried threads beneath a work piece and a spreader for forming loops in a cover thread to lay the cover thread beneath the needle-carried threads-on the upper surface of the work piece. The machine differs in a broad sense from those conventional flat-bed machines which form similar multi-needle stitches in that it embodies the desirable characteristics of lowsilhouette frame structure and quiet, smootho peration and the cover thread and a separate take-up, for the.

looper thread. The spreader having this particular movement and the cover thread guiding arrangement cooperating therewith for laying a cover thread are believed to be novel whether they are combined with the particular needle actuating, or looper or take-up mechanisms disclosed herein or are combined with othe mechanisms for the same general purposes.

BACKGROUND OF THE INVENTION U.S. Pat. No. 1,707,068 granted Mar. 26, l929-to Rubel discloses a flat bed sewing machine which has three needles, a looper, a spreader and a cover thread guide all arranged to form a flat seam of the type formed of the machine of the present invention/In this Rubel patent both the spreader and the cover thread guide are mounted on vertical axes for-oscillatory motion relative to one another in horizontal planes above the work piece.

U.S. Pat. No. 2,107,918 granted Feb. 8, 1938 to Thompson et al discloses a multi-needle flat bed sewing, machine in which a spreader which oscillates about a.

vertical axis cooperates with a fixed cover thread guide and a cover thread eyelet which moves'vertically with theneedles for laying a cover thread. This particular patent discloses the cover thread handling and looper mechanisms as used in a currently manufactured flat bed machine but for a more extensive disclosure of the operation of the spreader, cover thread guide and 'eyelet reference is made to an earlier U.S. Pat. No. l,405,855 granted Feb. 7, 1922 to Moffatt wherein similar mechanism is used. In theseThompson, and Moffatt disclosures the cover thread guide is fixed close to the plane of oscillation of the spreader and it is provided with a curved slot through which the cover. thread extends after it has passed downwardly through.

an eyelet which moves up and down with theneedles. The combined motions of the spreader and the eyelet cause the cover thread to slide back and forth between.

stable positions at opposite ends of the curved slot, thus to position the cover thread ahead of one needle and behind the other. The present invention adapts a cover thread guide and vertically movable eyelet arrangement similar to that shown in these patents for cooperation with a spreader which reciprocates in a horizontal straight line path.

U.S. Pat. Nos. 2,636,462 granted Apr. 28, 1953 to Peterson et al., 2,704,042 granted Mar. 15, 1955 to Wallenberg et al., and 3,101,686 granted Aug. 27, 1963 to Hayes, as well as U.S. application Ser. No. 35,450 filed May .7, 1970, now U.S. Pat. No. 3,688,71], by Szostak et al., are illustrative of the development of the over-edge sewing machines having low-silhouette, compact frame structures and which run quietly and smoothly at very high operating speeds. As will be pointed out hereinbelow the machine of the present invention embodies these general features of such over-edge machines in a flat seam sewing machine. The overedge machines disclosed in the patents and the copending application just referred to employ a looper, an overedge looper and an underedge looper to cooperate with a plurality of needles to form the overedge stitches. The looper disclosed in the present application is the same as that disclosed in said application Ser. No. 35,450, while the overedge and underedge loopers, disclosed in said copending application and said patents, along with trimmers and other equipment peculiar to overedge machines are omitted from the machine of the present invention. From the standpoint of background however, it should be noted that the overedge loopers in said patents and said copending application are mounted on horizontal shafts having both oscillating and reciprocating motions.

U.S. Pat. No. 659,482 granted Oct. 9, 1900 to Klemm discloses a single needle overedge sewing machine in which a looper is carried by a bar which reciprocates without oscillatory motion in a horizontal plane above the work piece.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front view of a machine embodying the present invention, the view being partly in elevation and partly in section;

FIG. 2 is a vertical sectional view taken along the line 2--2 in FIG. 1;

FIG. 3 is an elevational view taken from the left-hand side of FIG. 1;

FIG. 4Jis a fragmentary plan view with parts in section;

FIG. 5 is a fragmentary elevational view, taken from the right-hand side of FIG. 1 and showing certain parts in section;

FIG. 6 is a fragmentary elevational view, taken as is F IG. 3, and showing certain parts in section;

FIG. 7 is a fragmentary vertical sectional view showing the looper thread control means;

FIG. 8 is a detail elevational view, with parts in section, showing the needle carrying and driving means;

FIG. 9. is an enlarged rear view of the presser foot;

FIG. 10 is an enlarged left-hand side view of the FIG. 13 is a perspective view of stitch type 605 as produced by a machine embodying the present invention;

FIG. 14 is a fragmentary top plan view illustrating the operation of the cover thread laying mechanism;

FIG. is a view similar to FIG. 14 but showing the parts in a different position; and

FIG. 16 is a perspective view of the needle and cover thread eyelets and the common take-up member which operates on the needle and cover threads.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The embodiment of the invention illustrated herein is a sewing machine for forming flat seams which has the characteristics of smooth and quiet operation at very high speeds and a low-silhouette frame structure heretofore possessed by certain overedge stitching machines. The mechanism and the frame structure are similar in many respects to that shown in co-pending U.S. application Ser. No. 35,450 filed May 7, 1970 by Szostak et al, which in turn is similar in many respects to U.S. Pat. No. 3,101,686 granted Aug. 27, 1963 to Hayes. However, the present embodiment differs substantially from said application and patent in that it is a multiple-needle machine for forming flat seams and in particular is adapted to form seams embodying a stitch type 605 in work pieces wherein the greater depth of throat afforded by earlier types of flat bed machines may not be required. Thus, for instances, the present embodiment will serve admirably for attaching elastic waistbands to knitted undergarments, attaching borders to the neck and armholes of knitted athletic shirts, and attaching cuffs and collarettes to knitted undergarments.

As shown in the present drawings the embodiment of this invention is contained within a low-silhouette frame structure which houses most of the operatingmechanism of the machine. Housing 10, as best shown in FIGS. 1, 2 and 4, has a main section 11 with a bottom plate 12 secured thereto for retaining a quantity of lubricant in the base portion of the frame to insure proper lubrication of most of the relatively moving parts of the machine which have some frictional engagement. A frame section 13, which is shown as a separate element of the frame structure, assists in providing an open space within the frame of the machine for receiving various operating parts. The frame section 13a (FIG. 1), carries a spring-retaining housing 13b which, in a well known manner, carries a spring for urging a presser foot 130 downwardly to retain work pieces against a work supporting surface or throat plate 1 la that extends horizontally within a plane about midway of the overall height of the-machine. The top of the frame is provided with a closure section 14 which is preferably removably attached to the portion 13 of the frame so as to normally enclose the main housing portion of the frame but which permits access when necessary, to the interior of the housing.

Suitably journalled within the frame 11 in a manner more fully disclosed in the above-mentioned Hayes patent is a main drive shaft 15 which as viewed in FIG. 1, extends outwardly beyond the righthand side of the housing. The righthand or outward end of shaft 15 has secured thereto a conventional pulley 15a and a hand wheel 15b by which the main drive shaft 15 may be rotated. As is usual, a suitable belt connection is provided from an electric motor and clutch unit to pulley 15a for normally rotating the main drive shaft 15 at a comparatively high speed when the clutch is closed under mechanical or automatic control.

The machine embodying the present invention is provided with a relatively light-weight needle carrier member 16 (see FIG. 5) having

bearing members

16a and 16b which surround a guide member 17. As is the case in said application Ser. No. 35,450, the guide 17 is held in a fixed position extending vertically in order to provide a vertical path for reciprocation of needles carried by the needle carrier 16. Also, as shown in said application Ser. No. 35,450, adequate provision is made for lubrication between the bearing

members

16a and 16b and the vertical guide 17.

Reciprocation of the needle carrier 16 in a vertical direction is accomplished by an arm 18 secured to a shaft 19. The outward end of arm 18, as more fully described in said application Ser. No. 35,450, carries a pin 180 (see FIG. 8) on which is journalled a roller element 18b which cooperates with a U-shaped surface 16e of the needle carrier 16. As will be apparent, rocking of thearm 18 about the shaft 19 will cause vertical movement of needle carrier 16 as a result of the rolling contact between the roller 18b and surface 16c of the needle carrier. Rocking movement is imparted to the shaft 19 on which arm 18 is secured by connections typical of a machine of this character. Thus (referring to FIG. 2) a pitman 20 having an enlarged portion 20a at its lower end is connected by suitable anti-friction bearings with a crank portion 15a of the main drive shaft 15. At its upper end the pitman 20 carries a pin 200 by which the pitman is pivotally connected with an arm 21 secured to the shaft 19 whereby rotation of the main drive shaft 15 produces oscillation of the needlecarrier actuating shaft 19.

Referring now to FIG. 5, the lower portion of the needle carrier 16 is provided with a needle retaining portion 160 adapted to receive the upper ends of a plurality of needles, indicated generally at N in said FIG. 5, and which will be described in more detail hereinbelow.

Referring now to FIG. 1 it will be observed that there are three needles N1, N2 and N3 mounted in the needle retaining portion 16c of the needle carrier 16. It will be understood that three such needles will be provided' when it is desired to form a flat seam which includes three parallel rows of chain stitches. However, it will be further understood that only two needles may be used in those instances wherein it is desired to produce two rows of parallel stitching.

Still referring to FIG. 1, it will be observed that the needlesN, separately identified as N1, N2 and N3, are supplied respectively with threads TNl, TN2 and TN3 from a suitable source (not shown) and through guiding and take-up means to be described hereinbelow.

As shown in FIG. 1 a looper 22 is positioned to work beneath the throat plate or work supporting portion 11a of the frame of the machine. The looper 22 is operated, by means similar to or identical with that shown in said application Ser. No. 35,450, for reciprocation horizontally towards the right and left, as viewed in FIG. 1, and for limited rocking or avoiding movement about'the axis of a hollow looper bar 23. Brief refer;

ence to FIG. 3 at this juncture will reveal the location 7 of the looper 22 and bar 23 relative to the needles as viewed from the lefthand end of the machine. Referring back to FIG. 1, the looper bar 23 is arranged for longi tudinal reciproctory movement and also for oscillatory movement thus to produce the looper motions deand cooperates with the lower end of va pitman- 28, the

upper end of which cooperateswith a spherical portion 29 of a crank 30 formed on the main drive shaft 15.

Thus, rotation of shaft 15 is transmitted, through the 1 linkage just described} to the looper bar 23 to reciprocate the same towards the right and left in a smooth and noiseless fashion. The looper bar 23 extends through means including a cam guide sleeve 31 which is con-: centric with and secured to a looper barsleeve 32"immediately surrounding the looper bar 23. The inner'or looper bar sleeve 32 is held against lengthwise move-: ment and is mounted in

bearings

33 and 34 for oscillation about the axis of the bar 23. Referring to FIGS. 1 and 2 it will be observed that the outer or cam guide sleeve 31 and the inner looper bar sleeve 32are slotted, as indicated at 35, to receive a cam block 36 pinned to the looper bar 23. Thus the cam block 36 may slide back and fourth in the slots incident to reciprocation of the looper bar 23 along its axisjrelatively tothe

sleeves

31 and 32. The

sleeves

31 and 32 are secured by a set-screw 31a to a link 37 and a looper avoid connecting rod 38 the upper end of which is carried by a crank section (not shown) on the main drive shaft 15.

The rocking motion thus imparted to cam guide sleeve, 31 about the axis of looper bar23 is imparted to bar 23 viewed in FIG. 1 imparted to looper-.22 by lengthwise reciprocation of looper bar 23 is quite extensive inasmuch as the looper 22 is designed for cooperation with three needles in the forming of typical chain stitches by interlocking a looper thread TL with the needle threads TNl', TN2 and TN3. The oscillatory motion imparted rected from a suitable source (not shown) to a bracket 40 and through an eyelet 42 from which it extends downwardly to a looper thread take-up mechanism 44' and thence upwardly through an eyelet 46 on looper 22 to the active part of the looper. The looper take-up mechanism 44 is the same as that shown in said application Ser. No. 35,450. Thus in FIG. 7 it will be observed that the looper take-up mechanism 44 includes a cam 48 fixed upon the main drive shaft 15, a support plate 50 and a castoff plate 52 between whichthe looper thread TL is passed. Actuation of the looper't'ake up mechanism 44 is properly timed with respect to' the movements of the looper 22 beneath the throat plate 1 1a, so as to tighten the looper thread around the needl'e threads in customary manner. v

The lefthand end portion of the drive shaft- 15 as viewed in FIG. 1 also carries suitable eccentrics for reciprocating feed bars 54 and 56 (also see FIG. 3) which in turn carry

conventional feed dogs

58 and 60 which operate through appropriate slots 62 in the throat plate Ila (alsosee FIG. 12).

The various parts of the machine as so far described in detail are either identical with or very similar'to corresponding parts in said application Ser. No. 35,450. It will be appreciated that several components of the machinedisclosed in said application are omitted from the present machine, such omitted parts being those that are intended to cooperate to perform the overedge stitching operation disclosed in said application. How ever the parts now to be described differ in structure and functionfrom anything disclosed in said application Ser. No. 35,450, and are specifically provided for the'purpose of cooperating with the parts already described in the formation of flat seams, for example, seams embodying a stitch type 605.

In the present machine, as viewed first in FIG. 1, a spreader 64 is fixed to the lefthand end of a spreader shaft 66 journalled in a bearing 68 for axial horizontal reciprocation devoid of any oscillatory movement about the axis of shaft 66. The shaft 66 is reciprocated by a Y-shaped link 70 which, in turn, is driven by a bell crank lever 72 pivoted on a cross shaft 74 and connected by a spherical end piece .76 with a pitman 78 the lower end of which is driven by a crank portion (not shown) on the main drive shaft 15. The Y-shaped link 70(see FIG. 4) is connected at end one to a pin 80 secured to the spreader shaft 66 by a set screw 82. At its other end the link 70 is connected to the fork 84.01 bell crank 72 by a pin 86' (see FIG. 1). By connecting the link 70 as just described between the bell crank.72 and spreader shaft 66 it is assured that the shaft 66 will be reciprocated longitudinally while being held against any' rotational movement abouts its own axis. In this connection also see FIG. 4 wherein the disposition of the link 70 with respectto the shaft 66 is shown in plan.

. just ahead of the needles and above the work supporting surface (not shown in'FIG. 3) of throat plate 11a. Referring back to FIG. 1 the lefthand end of the laterally'extending portion of spreader. 64 is bifurcated to form a thread receiving slot 88. The position of the spreader64 shown in FIG. 1 is'that assumed at the end of lefthandreciprocation of the spreader shaft 66 and in this position it will be notedthat the thread engaging slot 88 is well to the left of the vertical paths of the needles N. The position thus shown' in FIG. 1 corresponds with that shown in the detailed view in FIG. 14. The po= sition assumed by the spreader 64 at the righthand end of its excursion is-shown in the detailed FIG. 15. As will be apparent from FIG. 14 the I lefthand end of the spreader 64 is not only bifurcated to form the slot 88 but also the upper arm of the bifurcated end is cut off at an angle as indicated at 90 in said FIG. 14 so as to retain the cover thread TC during the leftward stroke of the spreader 64.-

The cover thread TC, FIG. 1, extends from a suitable source, not shown, through an eyelet 92 in bracket 40, an eyelet 94 in bracket 96 and downwardly through an eyelet 98 in a bracket 100 mounted on the needle carrier 16. From eyelet 98 the cover thread TC extends downwardly to a cover thread guide 102 and through a guide slot 104 formed in guide 102. The cover thread guide 102 is adjustably secured by screws 106 working in slots 108, to a bracket 110 on the machine. The cover thread guide 102 includes a downwardly extending leg 112 which positions the downwardly inclined portion of guide 102 (see FIG. 3) in which slot 104 is formed just above the plane in which the spreader 64 reciprocates. The operation of the spreader 64 and cover thread guide 102 in cooperation with the cover thread TC will be described after the following descrip-v tion of the take-up-mechanism which operates not only upon the thread TC but also upon all of the needle threads N.

As mentioned above the source of supply of the several threads used in this machine has not been shown.

Ordinarily such source may comprise an appropriate number of spools on a spool stand. Also, there has not been shown herein the thread tensioning mechanism for applying individually adjustable tension to each of the threads. Such a mechanism is shown in said application Ser. No. 35,450 and it or any other suitable mechanism may be employed with the present machine. Referring now to FIG. 4 the threads TL, TC and TN], TN2 and TN3 coming from suitable tensioning mechanism enter the machine from the upper left hand portion .of FIG. 4. The looper thread TL goes directly to eyelet 42 in bracket 40 and from there to the looper thread take-up mechanism as has been described above. The needle threads TNl, TN2 and TN3, and the cover thread TC, however, enter a common take-up device indicated generally at 114 in FIG. 4 and from there extend through a bracket 116 having four eyelets (not shown) to the bracket 40.

The course of cover thread TC from bracket 40 to the cover thread guide 102 has been described above.

The needle threads TN 1, TN2 and TN3 pass through suitable eyelets, not numbered, in bracket 40 and from there extend through suitable eyelets, not numbered, in bracket 96. From bracket 96 the needle threads extend, see FIG. 1, through a three-eyelet bracket 118 on the upper part of needle carrier 16 and through three eyelets, not numbered, in bracket 100 on the lower part of needle carrier 16, to the eyes, respectively of the three needles N1, N2 and N3.

The common take-up mechanism 114 referred to i above in connection with FIG. 4 includes a take-up member 120 secured to a clamp collar 122 adjustably mounted on the needle actuator rock shaft 19 for oscillating motion therewith. Referring now to FIGS. 6 and 16 the takeup member 120 cooperates with a bracket 124 having laterally spaced portions 126 and 128 (see FIG. 16) which straddle the take-up member 120 and which respectively, are provided with

upstanding portions

130 and 132 each having four eyelets (not numbered) for the threads. The bracket 124 is adjustably secured to the upper surface of the machine frame by a screw and slot connection 134, 136 (see FIG. 6) and also is provided with the bracket 116 having four eyelets (not numbered) for the threads to guide them to bracket 40 described above.

In all of the figures of the drawing except FIGS. 15 and 16 the parts are. shown in the positions assumed when needles N are in their uppermost position withdrawn from a work piece and ready to start donwardly toward the work piece. In FIG. 15 the parts. are shown in the positions assumed when the needles N are in their lowermost position, extending downwardly through the work piece and ready tostart upward motion. In FIG. 16 it may be assumed that the needles have started moving downwardly.

Referring now to FIG. 16 the needle threads TNl, TN2 and TN3 and the cover thread TC enter the takeup mechanism 114 where they are threaded individually through the eyelets in upstanding portion 132 of bracket 124. From those eyelets all of the threads extend into contact with the forward surface of take-up member and then individually through the eyelets in upstanding portion and bracket 116. As will be apparent from FIG. 16, with reference particularly to FIGS. 3 and 6 forward or clockwise rocking of the takeup member 120 will exert a pull on all of the needle threads and the cover thread within the span between the

upstanding portions

130 and 132 of bracket 124. Such rocking occurs during the downward stroke of the needles and the pull exerted on the threads by member 120 is effective to withdraw lengths of the threads from the supply and tensioning means and also is effective, acting against the tensioning means, to draw backwardly on the needle and cover threads. The pull-off and take-up actions required for forming the stitches are thus performed, the unique feature here being that a common take-up and pull-off mechanism is provided to act upon all of the needle threads as well as on the cover thread.

Since the illustrated embodiment of the present invention employs three needles N1, N2 and N3 the presser foot and the throat plate shown herein are adapted for operation with three needles, although, as noted above, there may be instances wherein the user may require only two needles. The presser foot indicated generally at 130 in FIG. 1 is shown in FIGS. 9, 10 and I1 and it includes a presser foot bottom 140 which is adapted to be yieldingly pressed downwardly on a work piece, when required, by the arm 142 (FIG. 3) which, in turn, is pressed by the spring contained within spring housing 13b (FIG. 3). The presser foot bottom 140 is provided with an opening 144 of suitable size to accommodate the three needles N 1, N2 and N3. The throat plate 11a, FIG. 12, in addition to the slots 62 through which the

feed dogs

58 and 60 work; is provided with an opening, generally indicated at 146, which is shaped to accommodate the three needles N1, N2 and N3.

7 As will have been observed in connection with FIG. 1 the needles are soset in the needle holder 16 that the points thereof lie at different levels, the pointof needle N1 being at a lowermost level, the point of needle N2 being at an intermediate level and the point of needle N3 being at an uppermost level, all with respect to the plane in which a work piece is supported on throat plate 110. Still referring to FIG. 1 it will be noted that the cover thread TC, as it extends from slot 104 of cover thread guide 102 tr the thread-receiving slot 88 at the bifurcated end of spreader 64, extends in front of the two left-hand needles N1 and N2 and at a level above the points of these two needles, while it extends at a level beneath the point of the right-hand needle 9 N3. Bearing in mind that the needles N1, N2 and N3 are in the uppermost position in the path of vertical reciprocation as shown in FIG. 1, attention is now directed to FIG. 14 wherein the parts are in that same position. In this FIG. 14 several previously formed stitches are shown, the fabric in which they are formed being omitted, and in the position of parts illustrated the

feed dogs

58 and 60 are in the middle of their feeding stroke whereby it may be assumed that the previously formed stitches are ready to continue moving towards the rear, that is, upwardly as viewed in FIG. 14, and that the needles N1, N2 and N3 are ready to start to move downwardly. The portion of the cover thread TC just discussed in connection with FIG. 1, extends in front of needles N1 and N2 and extends behind the axis along which needle N3 will descend as this portion of the stitching cycle proceeds. Therefore, as the needles move downwardly and

feed dogs

58 and 60 end their stroke, the needles N1 and N2 will penetrate the work piece behind said portion of the cover thread TC and the needle N3 will penetrate in front of said portion. At the time of penetration the previously formed stitches will have moved rearwardly into the position shown in FIG. 15 and upon completion of the downward stroke of the needles the take-up mechanism, described above, will have functioned to pull backwardly on cover thread TC, and the spreader 64 will have moved to the right releasing the cover thread TC, the position ofall of the parts at this moment being as shown in FIG. 15. Also, in this position the bracket 100 and eyelet 98 will have moved downwardly with the needles so as to lie very close to the upper surface of the cover thread guide 102.

In the portion of the stitch-forming cycle just de scribed the particular shape of the slot 104 in cover thread guide 102 and the relation between said slot and the eyelet 98 in bracket 100, which moves with the needles, and the straightline path of movement of spreader 64, have played an important part in achieving desired disposition of the cover thread TC beneath the needle threads on the upper surface ofa work piece. Thisbest may be understood by describing the succeeding halfcycle as if it were leading up to the position of parts shown in FIG. 14. Thus, starting with FIG. 15, the needles will begin to move upwardly, the take-up mechanism 114, due to counterclockwise rocking of member 120 (FIG. 16), will start to let off the needle and cover threads and the spreader 64 will start to move toward the left as viewed in FIG. 15. The advancing spreader 64 will engage the cover thread TC beneath the cover thread guide 102 and as let-off continues will form a loop in the cover thread by pulling thread downwardly through eyelet 98 and the slot 104, eventually to position the cover thread TC as it is shown in FIG. 14. In the meantime eyelet 98, in bracket 100, is moving upwardly with the needles, thus progressively lengthening the use of the illustrated embodiment of the invention.

the span of thread TC extending downwardly from eyelet 98 to slot 104 in cover thread guide 102. Still referring to FIG. 15 it will be observed that the slot 104 is elongated and has a dog-leg with a high point 148 about midway of the length of the slot. Instead of a dog-leg shape as shown the slot 104 could be curved to provide a high point equivalent to the high point 148. The purpose of the particular shape of slot 104 is to assure that the cover thread TC will move into a stable position-at thread at any given moment. Thus, when the needles N1, N2 and N3 are down, as in FIG. 15, and the eyelet 98 is very close to the cover thread guide 102, the length of cover thread TC extending upwardly from the last stitch formed by needle N3 through the slot 104 and to the eyelet 98 will tend to lie at a forwardly inclined angle widely divergent from the vertical. Instead however, the changingrelationship of parts will slide the thread TC forwardly along slot 104 so as to reach a stable position at the lower end thereof as viewed in FIG. 15. This forward pulling of the cover thread TC will have been effected by the increasing horizontal component of force exerted thereon as the needles and eyelet 98 were moving downwardly toward the position shown in FIG. 15. Accordingly, as the needles and eyelet 98 start to rise and the spreader 64 moves forwardly to engage the cover thread TC beneath cover thread guide 102 the horizontal component of force diminishes and the vertical component increases with the result that the thread TC will be pulled to the opposite end of slot 104 to assume the position shown in FIG.

To assist in understanding ofthe movement of the cover thread TC, just described, reference is made to FIG. 3 wherein the solid line positions of parts are those assumed when the needles N are up. The path of cover thread TC from eyelet 98 to cover thread guide 102 is relatively long and not much inclined from the vertical. However, in the broken line position of certain parts in FIG; 3 the bracket 100 and eyelet 98 are shown in

positions

100A and 98A and the path of thread TC is shown in a position TCA which would be assumed when the needles are down in the position indicated at NA. From a comparison of these two paths for the cover thread TC the reason for movement of the thread from one end to the other of slot 104 will be clear/Also, it will be apparent that when the cover thread is in position TCA, in FIG. 3, it lies directly in the pathof travel of spreader 64 so that the slot 88 thereof will engage the cover thread to carry the same into the loop illustrated in FIG. 14 during upward movement of the needles.

Referring back to FIG. 14 it now will be understood that because'the cover thread TC has moved to the rearward,-or upper, end of slot 104 during the rise of the needles the straight-line movement of spreader 64 has formed a loop in the cover thread TC wherein the length of thread extending from slot 104 to the thread engaging surface 90 of the spreader lies at an angle starting from behind needle N3 and extending in front of needles N1 and N2. This is the position at which the above description of operation started and the machine I is now ready for repetition of the complete cycle.

In FIG. 13, several stitches are illustrated in a perspective view. These are stitches of the type formed by It will be understood that instead of using three needles to form the illustrated stitch, one may use two needles or more than three needles, if desired, which would one end or the other of slot 104 depending upon the resultant direction of the combined forces acting on the form stitches somewhat similar to those illustrated in FIG.13.

vVarious modifications and variations in details of the illustrated embodiment of the present invention may be resorted to by those skilled in the art without departing fromthe scope of the claims.

What is claimed is:

1. In a sewing machine, stitch forming devices for forming a flat seam comprising a plurality of needles reciprocable in a substantially vertical plane and each carrying a needle thread, a throat plate having a work supporting surface lying in a substantially horizontal plane and having an opening for passage of said plurality of needles through said throat plate, a looper carrying a looper thread and disposed beneath said throat plate for cooperation with said needles to form a plurality of parallel rows of stitches, and a spreader operating solely in a straight line reciprocatory motion wholly above said throat plate for laying a cover thread in position for engagement beneath all of said needle threads as said parallel rows of stitches are formed.

2. A sewing machine in accordance with claim 1 in which said straight line motion of said spreader is in a substantially horizontal path.

3. A sewing machine in accordance with claim 2 in which said spreader is carried by a shaft having a substantially horizontal straight line motion.

4. A sewing machine in accordance with claim 2 in which said spreader is carried by a shaft having a substantially horizontal axis and in which said shaft has only an axial reciprocatory motion.

5. A sewing machine in accordance with claim 2 in which said looper has a motion in a path which is substantially parallel with the path of said spreader.

6. In a sewing machine, stitch forming devices for forming a flat seam comprising a plurality of needles reciprocable in a vertical plane and each carrying a needle thread, a throat plate having a work supporting surface lying in a horizontal plane and having an opening for passage of said plurality of needles through said throat plate, a looper carrying a looper thread and disposed beneath said throat plate for cooperation with said needles to form a plurality of parallel rows of stitches, a spreader operating solely in a straight line reciprocating motion wholly above said throat plate for forming a loop in a cover thread for penetration by certain of said plurality of needles, and cover thread guide means cooperating with said spreader to direct one strand of each loop in said cover thread between two adjacent needles.

7. A sewing machine in accordance with claim 6 in which said straight line motion of said spreader is in a substantially horizontal path.

8. A sewing machine in accordance with claim 7 in which said spreader is carried by a shaft having a substantially horizontal straight line motion.

9. A sewing machine in accordance with claim 7 in which said spreader is carried by a shaft having a substantially horizontal axis and in which said shaft has only an axial reciprocatory motion.

10. A sewing machine in accordance with claim 7 in which said looper has a motion in a path which is substantially parallel with the path of said spreader.

11. A sewing machine in accordance with claim 7 in which said cover thread guide means includes a guide plate fixed to said machine in a position closely overlying said spreader, and an eyelet mounted above said guide plate for movement with said needles vertically toward and from' said guide plate, and said guide plate having a curved elongated slot formed therein for passage of said cover thread from said eyelet and through said slot into the path of said spreader, the combined motions of said spreader and said eyelet relative to said guide plate causing said cover thread to slide between stable positions at opposite ends of said slot thus to direct said one strand of each loop in said cover thread between said adjacent needles.

12. A sewing machine in accordance with claim 11 in which said straight line motion of said spreader is in a substantially horizontal path.

13. A sewing machine in accordance with claim l2 in which said spreader is carried by a shaft havinga substantially horizontal straight line movement.

14. A sewing machine in accordance with claim 12 in which said spreader is carried by a shaft having a substantially horizontal axis and in which said shaft has only an axial reciprocatory motion.

15. A sewing machine in accordance with claim 12 in which said looper has a motion in a path which is substantially parallel with the path of said spreader.

16. A sewing machine in accordance with claim 1 in which there is provided a common take-up means for all of said needle threads and said cover thread.

17. A sewing machine in accordance with claim 6 in which there is provided a common take-up means for all of said needle threads and said cover thread.

18. A sewing machine in accordance with claim 11 in which there is provided a common take-up means for 'all of said needle threads and said cover thread.

' 1 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,77 57 Dated December M, 1973 Inventor(s) Henryk SCak It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page "Attorney James D. Ock" Q should be "James D.v Bock-- Col. 8, line 4 "donwar'dly" should be -downwardly Col. 8, l ne 63 "tr" should be -t ov I Claim 6, line 11 "reciprocating" should be --reciprocatory-- Name of Assignee should be changed fromd Union Special Machine Company" to --Union Special Corporation-- Signed and sealed this 23rd day of April 1971;.-

(SEAL) Attest:

EDWARD I' 'I.1*LETOHER,JR. C. MARSHALL DANN Attesting Officer Commissionerof." Patents

Claims

11. A sewing machine in accordance with claim 7 in which said cover thread guide means includes a guide plate fixed to said machine in a position closely overlying said spreader, and an eyelet mounted above said guide plate for movement with said needles vertically toward and from said guide plate, and said guide plate having a curved elongated slot formed therein for passage of said cover thread from said eyelet and through said slot into the path of said spreader, the combined motions of said spreader and said eyelet relative to said guide plate causing said cover thread to slide between stable positions at opposite ends of said slot thus to direct said one strand of each loop in said cover thread between said adjacent needles.

13. A sewinG machine in accordance with claim 12 in which said spreader is carried by a shaft having a substantially horizontal straight line movement.

18. A sewing machine in accordance with claim 11 in which there is provided a common take-up means for all of said needle threads and said cover thread.