US2740366A

US2740366A - Loopers for sewing machines

Info

Publication number: US2740366A
Application number: US377167A
Authority: US
Inventors: David B Scott
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1953-08-28
Filing date: 1953-08-28
Publication date: 1956-04-03
Anticipated expiration: 1973-04-03

Description

April 1956 'D. B. SCOTT 2,740,366

LOOPERS FOR sswmc MACHINES Filed Aug. 28. 1953 2 Sheets-Sheet 1 ig. I.

3 u xx m on 20 F; 24 23 m v k IO zzvmvrozz. David B. Scott BY ATTORNEY April 3, 1956 D. B. SCOTT 2,740,366

' LOOPERS FOR sswmc MACHINES Filed Aug. 28, 1953 2 Sheets-Sheet 2 INVENTOR. DCIVid B. Scoh WITNESS BY WK A QA W4 ATTORNEY Loornns non SEWING MACHINES David B. Scott, Plainfield, N. 5., assignor Manufacturing (fompany, tion of New Jersey Application August 28, 1953, Serial No. 377,167

3 Claims. (Cl. 112-400) to The inger Elizabeth, N. .I., a corpora- This invention relates to a thread-carrying looper for a two-thread chain-stitch sewing machine.

'An object of this invention is the provision on a 3 threaded looper of looper-thread guarding surfaces which are formed and arranged to obviate objectionable interference between the looper-thread and the needle-thread during stitch formation.

Other objects and advantages will be apparent from the following description and accompanying drawings of a preferred embodiment in which:

Fig. 1 is a fragmentary front elevational view, partly in section, of a two-thread chain-stitch sewing machine .-.having portions broken away to illustrate more clearly the thread-carrying looper and the looper actuating mechanism,

Fig. 2 is a front elevational view of the looper, Fig. 3 is an enlarged rear elevational view of the blade portion of the looper,

the position of parts and proper thread concatenation during loop seizure by the looper on the upstroke of the needle,

Fig. 7 is a cross-sectional view taken substantially along line 7-7 of Fig. 6,

Fig. 8 is a perspective view similar to Fig. 6 but illustrating an improper concatenation of thread as obtained frequently with a looper of usual construction, and

Fig. 9 is a cross-sectional view of the usual looper taken substantially along line 99 of Fig. '8.

Referring to the drawings, Fig. 1 illustrates a portion of a sewing machine having a frame including a bed 10 formed with a work-supporting cloth plate 11 which car- 'ries the usual throat-plate 12. Overhanging theibed is a gooseneck terminating in a sewing head 13 in which is journaled an endwise reciprocatory needle-bar 14, which carries a needle 15, and a presser-bar 16 to which is fitted a presser-foot 17. Rotatably journaled beneath the work-supporting cloth plate is a bed-shaft 18 which serves to impart a so-called four-motion path of movement to a thread-carrying looper 19 which thereby cooperates with the reciprocatory needle in the formation of two-thread chain stitches. The looper 19 is fixed to a carrier member 20 which is journaled for oscillation on a transverse stud 21 carried by a rock-shaft 22 which in turn is journaled in the bed 10 parallel to the axis of the bed-shaft.

Oscillation of the looper carrier about the transverse stud 21 provides two of the four looper motions, a needle-loop seizing movement, as illustrated in Figs. 6 and 8, and a loop-shedding movement, as shown in Fig. 5. Loop-seizing and -shedding movements are derived from a crank 23 on the bed-shaft 18 and are transmitted to United ates Patent of course; important.

ice

description of the looper-actuating mechanism, reference may be had to the U. S. March 28, 1944.

Theconstruction of my improved looper is best'illustrated in Figs. 2, 3 and 4. The looper is providedwith a base portion 30 from which dependsua stud 31'which is slabbed as at 32 so that the looper may be securedand properly located in the carrier 20 as by means'of a set patent of Clayton, No. 2,345,327,

screw. A looper blade 33 extends over the base portion and is joined thereto by a heel portion 34- which is formed with a thread-guiding eyelet 35 through which a looper thread is directed. The front face of the. looperblade, as viewed in Fig. 2, is formed with a thread-guiding slot 36 which extends from the eyelet 35 to an eye 37. At

'the rear face of the looper, which is best illustrated in Fig. 3, a shallow'and substantially vertical notch 38 is formed in the looper blade leading'directly to the eye 37. .T he rear face of the looper'is formed with a threadguarding recess-39 which extends lengthwise of the looper blade from a point adjacent the eye 37 toward the heel of the looper. As best shown inFig. 4, the thread-guarding recess 39 is formed at a point nearer the bottom. surface 40 of the looper thanis the threadeguiding slot 36 in the front face. The recess 39, moreover, is preferably formed over most of its length with substantially parallel sidewall portions 4141.

In the successful formation of two-thread chain stitches, proper interrelated movements of looper and needle are, However, it is of equal importance, particularly athigh rates of.sewing speed or when sewing conditions change rapidly as instarting or when a crossseam or obstruction is encountered, that proper concatenation of looper andneedle threads be maintained at the various critical points in. the stitching cycle. Interference between the needle and looper threads is a ;primary source of improper thread concatenation, for

.mal control and, therefore, do not concatenate properly at succeeding critical points 'in the stitching cycle, thus resulting in frequent thread breakage and loose or skipped stitches.

Figs. 5, 6 and 7 depict the relationship of looper and needle at two critical points during a cycle of stitch formation and illustrate the manner in which my improved looper serves to insure proper or desired concatenation of threads at each of these points. Figs. 8 and 9 illustrate the usual form of looper and show how thread interference occurs therewith. In these views, a needle thread is indicated as n while a looper thread is designated l. The arrow marked F indicates the direction in which the work is being fed while the arrow N shows the direction of needle reciprocation in each view. In Fig. 5, the arrow L indicates the direction of needleavoiding movement of the looper, while the arrow L shows the direction of loop-shedding movement thereof. In Figs. 6 and 8 the looper is partaking only of loopseizing movement the direction of which is indicated by arrow L In Fig. 5, the needle is shown descending through the work and the throat-plate rearwardly of the looper. The

combined effect of the feed of the work and the needleavoiding movement of the looper in the opposite directions results in the formation of a thread triangle for entrance by the needle. The thread triangle consists of one limb of looper thread extending from the work to the looper eye 37, a second limb of looper thread extending along the looper in the thread guiding slot 36, and the needle-thread loop of the previous stitch which is being shed by the looper. Of these parts of the thread triangle, the limb of looper thread from the eye 37 to the work is perhaps most critical. If this limb of thread is not properly controlled so that it does not extend in a substantially direct path between the work and the looper eye, as shown in Fig. 5, proper stitch formation will not occur. In particular, abnormal slack in the looper thread from the eye of the Work may cause the thread triangle to collapse and the needle in failing to penetrate the collapsed thread triangle will skip that stitch and thus produce a defective seam which may be unraveled easily.

In Figs. 8 and 9, a looper of usual construction is illustrated having a rear face 42 which is smooth and not provided with the thread-guarding recess 39 as in the looper of the present invention. In these figures, the looper occupies a position immediately after seizure of the needle-thread loop. As shown in the drawings, the limb of looper thread from the eye of the looper to the work must pass through the needle loop at this point. While this limb of looper thread is passing through, the needle loop is being drawn up by-the ascending needle so that the needle-thread loop is, in effect, being turned in a counterclockwise direction about the looper blade as viewed in Fig. 9. With a looper of ordinary construction, the looper thread is frequently caught up by the tightening needle-thread loop and carried with the needle thread in a counterclockwise direction about the looper, thus creating an abnormal bight in the looper thread which in the succeeding position of Fig. 5 results in a slack limb of looper thread from the eye of the looper to the work.

Referring to Figs. 6 and 7, my improved looper is illustrated together with the proper concatenation of thread which is dictated thereby. Should the looper thread be caught up by the tightening needle-thread loop, the looper thread will be carried into the thread-guarding recess 39 on the rear face of the looper blade, rather than being carried abnormally under and about the looper blade. As the needle-loop shifts toward the heel of the looper, the undistended limb of looper thread from the looper eye to the work will, therefore, assume a direct and proper path without objectionable slack.

The thread-guarding recess 39 is illustrated in Figs. 2, 3 and 4 in its preferred form. It is located beneath the level of the guide slot 36 and the looper eye 35 so as to be in position to receive and protect the looper thread should it be caught up by the needle-thread loop. The side walls of the recess 39 are preferably made substantially parallel to each other and are disposed substantially perpendicular to the rear face of the looper blade. By this construction, no projecting shelf or ledge is presented which might be struck by the needle point.

Having thus set forth the nature of the invention, what I claim herein is:

l. A thread-carrying chain-stitch looper having a blade provided with a free extremity, said blade formed with a transverse thread-accommodating eye adapted to receive a thread from one side of said blade and deliver said thread to the opposite side thereof, said blade being formed with a thread-guarding slot arranged substantially lengthwise of said blade, said slot being disposed to extend away from said free extremity from a point spaced not more than the width of said thread-guarding slot from the delivery end of said thread-eye.

2. A thread-carrying chain-stitch looper having a blade formed with a free extremity and a looper supporting heel extremity a transverse thread-eye formed in said free extremity, said blade being formed at one side with a thread-guiding slot adjoining said thread eye and adapted to deliver a limb of thread from a supply to said thread-eye, said blade being formed at the opposite side with a thread-guarding slot terminating at a point not more than the width of said thread guarding slot from said thread-eye and adapted to accommodate a limb of thread extending from said thread-eye, each of said slots extending from adjacent to said thread-eye toward the heel extremity of said blade.

3. A thread-carrying looper for a chain-stitch sewing machine having a reciprocatory work-penetrating needle and means actuated by said sewing machine for shifting said looper in timed relation with said needle reciprocation, said looper comprising an elongated blade having a pointed free extremity formed with a transverse threadeye adapted to receive a looper-thread at one side of said blade and deliver said thread at the opposite side thereof, said looper-blade being formed adjacent the thread delivery side thereof with a looper thread guarding slot extending lengthwise of said looper-blade from a point not more than the width of said thread guarding slot from said thread eye and in a direction away from the free extremity of said blade, said thread-guarding .slot having parallel side-Wall portions disposed substantially perpendicular to the path of reciprocation ofsaid needle.

References Cited in the file of this patent UNITED STATES PATENTS 1,115,086 Moffatt Oct. 27, 1914 FOREIGN PATENTS 6,037 Great Britain 1912