US2178543A

US2178543A - Lock stitch sewing machine

Info

Publication number: US2178543A
Application number: US92540A
Authority: US
Inventors: Charles F Rubel; Clarence C Smith
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1936-07-25
Filing date: 1936-07-25
Publication date: 1939-11-07
Anticipated expiration: 1956-11-07
Also published as: FR821859A; US2178544A; GB502792A; GB510009A; DE881750C; DE876030C

Description

Nov. 7; 1939. -c. F. RUBEL ET AL. 2,178,543

LOCK STITCH SEWING MACHINE Filed July 25, 193? 4 Sheets-Sheet 1 W I TNESSES:

NW. 7, 1939. c. F. RUBEL ET AL 2,178,543

LOCK STITCH SEWING MACHINE Filed July 25, 1936 4Sheets-5heet 2 l llll INVENTORSI Charles :Ffiuize .& CZarznw C. ,Smzfib,

RNEYS.

Nov. 7, 1939. c. F. RUBEL ETl' AL 2,178,543

'LOCK STITCH SEWING MACHINE Filed July 25, 1936 4 Sheds-Sheet 3 FIG; 112: 17 4:5 55 J7 56 55 65 2 5776 05 51 :97

. 11.0 v"; f 8 x WITNESSES- INVENTORS:

Nov. 7, 1939. c F RUBEL ET AL 2,178,543

LOCK STITCH SEWING MACHINE Filed July 25, 1936 Sheets-Sheet 4 WITNESSES: 1 NV ENTOR:

. TORNEYS. 7 f

TES

PATE'l oFr-ic LOCK STITCH SEWING MA 3' Charles F. Rubel and Clarence C. Smith, Chicago,

Ill, asslgnors to Union Special Machine Company, Chicago, 111., a corporation of Illinois Application July 25, 1936, SerlalNo. 92,540

47 Claims.

I chines of the rotary hook type for producing lock stitch seams.

The maximum speed at which lock stitch sewing machines can be safely operated depends almost wholly upon three factors, to wit: the amount of strain induced in the needle thread when loops are drawn therefrom by the rotating component or rotary hook ofthe complemental stitch-forming means; the aggregate weight of the non-rotating component of said means and a thread supply within it, which component may constitute a holder for a separate bobbin case, said aggregate weight determining in direct proportion to its magnitude, the degree of friction between the bearing surfaces of said holder and the rotary hook; and the areas of the aforesaid bearing surfaces. In lock stitch sewing machines asordinarily constructed, the bobbin carrier orclose working fit. The bearing surfaces oi the rib and the groove are thus necessarily of considerable diameter, and since the consequent linear velocity, at high speeds, approaches and in some cases exceeds three thousand feet per minute, excessive heat is generated between them. Such heating causes rapid wear between the hook and the bobbin case holder, and in turn entails frequent renewals at a considerable outlay both from the standpoint of cost of the replacement parts and the time consumed in installing them. As the raceway of the rotary hook wears away, malformed or drunken stitches are produced by reason of vibration or wobbllng of the bobbin case holder within the hook, and the needle thread is often ruptured as a consequence of being pinched between the rib and the rear side of the race- ,way as the clearance in this region enlarges. Still another drawback common to ordinary lock stitch sewing machines is that a retaining latch means is embodied in the construction of the bobbin case, which not only adds to the weight of the case, but, due to the space required for its accommodation, proportionately reduces the tread capacity of said case. 7

Our invention is directed toward overcoming the above mentioned drawbacks, l. e., making feasible the operation of lock stitch sewing machines at much higher speeds than possible heretofore and securing a correspondingly increased output from them, and moreover toward obviating frequent replacements of worn parts of the complemental stitch-forming means as was necessary heretofore. This desideratum we realize in practice as more fully explained later, by making the internal groove of the rotary hook considerably wider than the circumferential rib on the bobbin carrier or bobbin case holder so that the latter may have limited axialplay relative to the hook and by providing a separate extraneous element in the form of a retractable keeper with spot projections for engaging the front of the bobbin 10 case holder and the bobbin case and operative in lieu of the usual latch means, to retain the bobbin case within the holder and at the same time determine the operative position of the holder within the rotary hook such that the front face of the rib is at all times prevented from contacting the front side of the groove, and the rear face or shoulder of said rib from normally contacting with the inner side or corresponding shoulder of the groove; by allocating the spot projections on the keeper so as to be traversed by the outer limb of the needle thread loop when said loop-is under the least tension and moving relatively slow across the exposed front faces of the bobbin case and holder, whereby the axial play between the rib of the latter and the hook groove is momentarily reduced and substantially taken up if need be and said holder temporarily restrained to insure against pinching and/or cutting of the needle thread between the rib and the inner side of'the 80 groove by providing for adjustment of the keeper plate to enable taking up, from time to time, of v wear between the inner shoulder of the rotary hook and the thrust resisting shoulder of the bobbin case holder; by resorting to theuse of thin as light metal in the construction of the bobbin case and the bobbin: and by making the bobbin case holder of open construction as far as possible consistent with the necessary strength, so as, on the one hand, to decrease its weight and facilitate 40 passage of cooling air through and about it, and on the other hand, to reduce the surface thereof which is traversed by the needle thread as it passes around the back of the'bobbin within said holder.

A rotary hook organization so constructed does 5 not require either air blast cooling or lubrication and is thus also advantageous in that it is immune agalnstbecomlng clogged or covered by adhering and heat-retaining lint. The. possibility of lint accumulation on the stationary or nonrotating components of the hook structure is further minimized by reason of the reduced surfaces.

of these parts.

In the attached drawings, Fig. I is a fragmentary view. partly in elevatlon and partb in longitudinal section, of a lock stitch sewing machine conveniently embodying our invention.

Fig. II is a cross section taken as indicated by s thearrows lIIIinFlg.I.

Fig. III is a fragmentary plan view of the forward end of the horizontal work support of the machine, with a portion of said support broken out, and with the underlying parts shown in sec- 10 tion taken as indicated by arrows lI[III in Fig. IV is a fragmentary detail section drawn to a larger scale and taken as indicated by the arrows IV-IV in Fig. III.

5 Fig. V is a fragmentary detail sectional view,

likewise on a larger scale, and taken as indicated by the arrows V-V in Fig. IV. Fig. VI shows the top plan view of the bobbin case holder associated with the rotary hook of go the machine.

Figs. VII and VIII respectively are front and rear perspective views of the holder for the bobbin case.

' Fig. 1:: is a perspective view of the bobbin case;

"and

Fig. x is a detail view partly in elevation and partly in section taken as indicated by the arrows x--x in Fig. V, showing how pinching and ,rupturing of the needle thread loops is precluded through our invention.

The illustrated lock stitch sewing machine (Figs. I-II.I)"has a horizontal bed plate or work support I overhung by an arm 2 with a terminal head 3 which aflords guidance to a vertical re- 35 ciprocating bar 4 carrying a needle 5 at its lower end. Enrouteto the needle I, the needle thread N (Fig; 1) passes from a suitable source of supply (not shown) through a fixed, guide 8, then through a tension device I, then under a fixed guide finger 8 at one; side of the head 3 and finally through the eye of the ve'rtically oscillatins finger I of a take-up mechanism (not illustrated) within said head, which mechanism is preferably like that featured in a co-pendins 45 patent application Serial No. 753,671 filed by Carl 0. Nelson on November 19, 1934, and in which the rotating component revolves twice for each reciprocation of the needles. Also guided in the head 3 is a presser bar II to the bottom end of go which is afiixeda presser foot ll of customary construction. Under the work support Mn line with the presser foot Ii, is a feeddog l2 whereof the tooth portions project upward through the slots of a removable plate I! set into the top sur- 55 face of said work support, see Figs. I and II.

The feed dog II'is secured with capacity for verticaladiustmenttoone'endofafeedbar llbya screw I, see Fig. II, the other end of said bar having a pivotal connection at I! with a rocker 50 II on an oscillating shaft It journaled in spaced 70 ble means indicated at I! in Fig. II, the swing of the rocker and hence the feed movement of the feed dog, may be varied at will. Up and h down or lift movements are imparted to the feed flog bar II by virtue of connection of the curved 75 underslung-arm I4 thereofQthrofigh a drop link neath the work support I is a complemental stitch-forming means which is comprehensively designated by the numeral 35 and with which the present invention is more especially concerned. As shown, this complements] stitchforming means 35 comprises a rotating component or rotary hook 38 which is afilxed to the left-hand end of a small diameter shaft 31, by a number of screws 38 passing through its axial boss or hub 39. As shown in Fig. III, the shaft 37 extends parallel with the rotary shaft 25 aforementioned, and is journaled immediately adiacent said hook, in an elongate bearing bushing 40 fixed in the lug 21. The annular space 4| (Figs. I and HI) within the bearing bushing 40 receives oil through a vertical duct 42 in the work support I; and disposed crosswise of said duct, is a wad 43 of cotton or the like capable of storing a considerable reserve supply of the lubricant. From Figs. I, III, and V, it will be observed that the rotary hook it has a pointed beak 44 for seizing the thread N of the needle I in the well known manner as said needle rises after having penetrated the fabric F (Fig. V). The rotary hook is also formed with the usual loop shedding tail 4', as well as with a loop deflector 46. Within' the rotating component 36 of the complemental stitch-forming means 35 is a non-rotating component which in this instance constitutes a holder for a bobbin case, see Figs. VI, VII and VIII. The bobbin case holder 41 has a circumferential rib 49 extending medially around its body, said rib being interrupted as at at the top to clear the needle thread loop L, see Fig. V. As theresult of this interruption the rib starts with a shoulder .52 which constitutes the needle loop detaining horn and terminates with a tapered shoulder 53 over which the thread loop is released, this end of the rib being cut away or narrowed at one side as shown at 54 in Fig. VI. As shown in Fig. IV the rib-49 of the bobbin case holder 4! beers upon a circumferential surface 55 of the rotary hook 36 formed Jointly by an annular shoulder 58 within said hook and a flanged segment 51 which is secured to the exterior of the latter by screws 58 and which provides the loop shedding tail 4!. It is to be especially noted from Fig. IV that according to our invention, the groove or raceway 55 is made considerably wider than the interengaging rib 49. At the front, the bobbin case holder 4l has the usual segmental face flange 59 (Figs. VI and VII) which extends part way around it, and which is thickened at the top as at 80. Avertical frontal notch II in the thickened top portion 60 of the face flange is loosely engages the lateral projection ll of a detaining finger Bl secured by screws 05 to the underside of the work support -I see Figs. I--IV. At one side of the notch 6| the thickened portion 60 of the bobbin case holder 41 is well rounded according to our invention as 'at ll leftward of the notch I for a purpose later on explained. Immediately behind the top of the face flange 59, the body of the bobbin case holder 41 is provided with the usual central needle clearing aperture 41, and crosswise of its back with the usual single diametral vertical web Cl which supports a forwardly-projecting axial stud 4!. As ordinarily, the portion of the body ll of the holder 41 forward of the rib 49 is in the form of a circumferential segment corr ponding in angular extent with the face flange in said rib, and at the ends of said face flange.

Instead of being annular as ordinarily, according to our invention, the rounded rear portion of the holder body 59 is reduced to the form of a circumferential segment semi-circular in extent andwhich provides a guard surface of correspondingly smaller, but nevertheless ample area for directing the needle thread over the back of the bobbin (hereinafter more specifically referred to) within the holder ll, said guard surface extending from the point or region at which the loop first makes contact with the-holder body to the point of loop release and being connected at its-ends 13 by the vertical diametral web 58 at the back of said holder. Obviously, a bobbin case holder lightened in its construction as just explained presents less surface on which lint could collect is equally advannotch 15 at its top to engage a projection 16- within said-bobbin case holder whereby it is held against rotation as the bobbin thread B is withdrawn during the formation of a seam. The

exposed outer face of the end wall of the bobbin case '14 is smooth and well-rounded to facilitate movement of'the needle thread N across it, and projecting inward from said wall is a tubular axial stud ill which telescopically flts over the axial stud 89 of the bobbin case holder 61 as shown in Fig. IV, and which thus serves as a mounting axis for the bobbin or spool 18.

The bobbin case 'M'is provided with a delivery aperture US-for the bobbin thread Bfand with a spring tension finger 86 which yieldingly resists withdrawal of the bobbin thread from the spool 718. The notch l5 and the two

openings

85 and 8% in the front wall of the bobbin case It serve to decrease the weight of the latter and set apart three. relatively narrow spoke-like web portions 83, M and 85 to form a supporting spider, from which the stud ll projects inwardly. The vertical web portion 85, it will be noted, is longer than the others and tapers upwardly for the purposes of a finwr grasp so that the bobbin can be easily removed from the front of the holder d'i.

. 'By virtue of the open formation of the bobbin case front, its'surface area is considerably reduced and the'likelihood of lint collection thereon mid to a corresponding extent.

e bobbin case it and the spool it which it encloses. are retained within the bobbin case holder 6'! by akeeper member in the form of a circular plate 811 whereof the axial shank 88 is.

required to the bobbin holder ll for removal of the bobbin case it and replenishment of the bobbin thread, the arm 89 carrying the keeper plate 8'! is swung downward about its pivot 90 to the position shown in-dot and dash lines in Fig.1,

which is substantially such movement being yieldingly resisted by a leaf spring 93, which, by engagement with the flat 94 of said arm, holds the latter depressed. In this connection, it will be noted that when the arm 99 is retracted, the bobbin case holder 41 is retained against falling out from within the hook component by encounter of the rib 49 with the front wall of the groove 55. Normally by cooperation with another flat 95 of the arm 89, the spring 93 operates to yieldin'gly hold said arm in its active elevated position against an adjustable stop screw 96 threadedly engaged within the fulcrum clevis of the bracket piece 9|. For a purpose presently explained, the keeper plate 81 is axially adjustable in the arm 89 toward and away from the rotary loop taker 35 by means of a regulating screw 91, and is fixable in adjusted positions by a set screw 98. As shown in Figs. I and IV and V, the keeper plate Bl has two substantially diametrically-aligned circumferentially-arranged spot projections 99 and M0 on its inner face between which and the out er faces of the bobbin case holder and the bobbin case, the outer limb of the needle loop is adapted to pass. The spot projection 99 corresponds in position with the radial web portion 83 of the bobbin case it and lying substantially in the plane a-a radial to the axis of the rotary hook .and passing through the end of the loop detaining horn of the latter, see Fig. V; while the projection I00 lies opposite the right hand portion of the face flange 59 of the bobbin case holder $1: In practice, the keeper plate Si is so adjusted as'to determine clearances between its spot projections 99 and Hill and the exposed outer face of the bobbin case M and the outer face of the face flange 59 respectively just wide enough to permit f ee passage of the needle thread N4 The keeper 8'8 thus acts to prevent, at all times,

contact between the rib on the bobbin case holder and t outer side of the groove in the rotary hook, and to determine a normal position for the bobbin case holder with the inner face or shoulder of said rib out of contact with the inner face or shoulder of the groove. Due to movement of theneedle thread across the faceof the bobbin case M and the face flange of the bobbin case holder 4! as just explained, said case and holder if need be are momentarily moved axially inward at these times to reduce and substantially take up the axial play so that'the rear face or shoulder of the rib 39 on said holder is brought closer to or into light bearing contact with the opposing shoulder 58 of the internal groove or raceway 55 in the rotary hook 36 and the holder in this way temporarily restrained. The bobbin case It and the holder 41! are thus effectively sustained against vibration and the needle thread prevented from being pinched between the rib 49 and the shoulder 56 of the raceway 55 at the loop-detaining horn 52 in the manner clearly shown in Fig. X since in practice the permissible amount of end play is made substantially less than the thickness of the needle thread. The adjustability of the keeper plate 8'!- is also advantageous in that it permits taking up of wear between the rib 49 and the shoulder 55, and moreover in that it enables adaptation of the sewing machine for use of threads of different gauges. By virtue of the lightness of the bobbin case holder 41, the bobbin case It and spool I8, and the relatively small contacting areas of the rib 49 and the shoulder 56, friction is reduced to a minimum so that lubrication may be entirely dispensed with and lint accumulation avoided. It

therefore follows that our improved sewing machine can be continuously operated at very high speeds without excessive heatingsuch as would cause rapid wear. As heretobefore stated, the

. I open construction of the parts allows free circuincreased-in fact, these parts can be used until the interengaging rib and groove have completely worn away. Providing that adjustments of the keeper plate 81 are made when necessary at protracted intervals to limit the working clearance and thereby preclude vibration of said holder in the hook. I I

From Fig. V, it is to be especially noted that the spot projection 98 of the keeper plate 81 is passed by the needle thread loop L when the latter is substantially fully drawn out and while the thread is moving at relatively slow rate across the face of the bobbin case 14; and that the other spot projection Hill is encountered by the needle thread after the needle loop has been fully drawn out as indicated in dot and dash lines and when the take-up 9 is pulling slowly on the thread. As a consequence of ,the specific allocation of the spot projections 99 and I00, practically no restraint is imposed upon the needle loop L to prevent or retard'its free move= ment around the bobbin case I! and the holder 41. The shaping of the face flange of the holder 41 at 88 leftward oi the notch 6| (Rigs. V and VII) obviates the usual abrupt shoulder for lodgment of the bobbin thread 13 on its way up to the point of stitch formation, and further eases the movement of the needle loops over the holder.

It is to be understood that the rotary hook it revolves twice for each reciprocation of the needle N as is the case in the Nelson application hereinbefore referred to.

Having thus described our invention, we claim:

1. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating hollow bobbin case holder retained within and by the rotary hook with capacity for limited axial play; opposing circumferential shoulders respectively on said hook and said holder; a bobbin case fitting within the holder; and separate means for maintaining the bobbin case in the holder with the circumferential shoulder of said holder normally out of contact with the circumferential shoulder of 55 said hook. I

2. In a lock stitch sewing machine, an axially hollow rotary hook; an axially-free non-rotating hollow bobbin case holder within the rotary hook; opposing circumferential shoulders respectively on said hook and said holder; means rotating with said rotary hook for keeping the bobbin case holder assembled with the rotary book; a bobbin case fitting within the holder; and separate means for maintaining the bobbin case in the holder with the circumferential shoulder of the latter normally out of contact with the circumferential shoulder of said hook.

3. In a lock stitch sewing machine, an axially hollow rotary hook with an internal circumferential groove, a non-rotating hollow bobbin case holder retained by andmounted within the rotary hook having an external circumferential rib narrower than the groove aforesaid; a bobbin case fitting within the holder; and separate means n for maintaining the bobbin case in the holder arvaua with'the circumferential rib of the latter at all times out of contact with the outer side of the groove in the rotary hook and normally out of contact with the inner side of said groove.

4. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating hollow bobbin case holder retained within and by the rotary hook with capacity for limited axial play; opposing circumferential shoulders respectively on said hook and said holder; a bobbin case iittingwithin the holder; and separate means coacting with the exposed face of the bobbin case to maintain the latter in the holder with the circumferential shoulder of the latter normally out of contact with the circumferential shoulder of the hook.

5. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating axially-free hollow bobbin case holder within the rotary hook; opposing circumferential shoulders respectively on said hook. and said holder; a bobbin case fitting within the holder; and a keeper with spot projections at spaced circumferential intervals for coacting with the needle thread loop and with the exposed faces of thebobbin case and the bobbin case holder respectively, to retain said case in the holder with the circumferential shoulder of the latter normally out of contact with the circumferential shoulder of thehook.

6. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating axially-free hollow bobbin case holder within the rotary hook; opposing circumferential shoulders respectively on said hook and said holder; a bobbin case fitting within the holder; and keeper means having spot projections between which andthe exposedfaces of the bobbin case and the holder the needle thread passes, whereby said bobbin case is retained in the holder with the circumferential shoulder of theJatter normally out of contact with the circumferential shoulder of the hook, said spot projections being circumferentially arranged and so allocated as to be cleared'at times when the movement of the needlethread across the face of the bobbin case is relatively slow.

7. In a' lock stitch sewing machine, an axially hollow rotary hook; and a non-rotating bobbin case holder supported within the rotary hook, said holder having an external circumferential rib engaging an internal circumferential groove of the hook, and an open body with a rounded cylindric segment rearward of the rib which segment provides a guard surface for directing the needle thread loop around the back of the holder, the length of the segment being limited to the distance between the point of initial contact to the point of release of the loop.

8. In a lock stitch sewing machine, an axially hollow rotary. hook; and a non-rotating bobbin case holder supported within the rotary hook,

said holder having an external circumferential "rib engaging an internal circumferential groove of the hook, and an open body with a rounded substantially semi-circular segment rearward of its rib which segment provides a guard surface for directing the needle thread loop around the back ofthe holder, and a vertical diametral web connecting the ends of the guard surface at the back of said holder.

9. In a lock stitch sewing machine, an axially Hollow rotary hook with a circumferential bearing shoulder, and an axially free non-rotating hollow bobbin case holder with an external circumferential bearing shoulderfor, engaging the shoulder of the rotary book,

said holder having an open body with a rounded cylindric segment rearward of its shoulder, which segment provides a guard surface for directing the needle thread loop around the back of the holder, the length of the segment being limited to the distance between the point of initial contact and the point of release of the loop.

10. In a lock stitch sewing machine, an axially hollow rotary hook with an internal circumferential bearing shoulder; and a non-rotating hollow bobbin caseholder with an external circumferential bearing shoulder for engaging the shoulder of the rotary hook, said holder having an 7 open body with a rounded substantially semi-circular segment rearward of its shoulder providing a guard surface for directing'the needle thread loop around the back of the holder, and a vertical diametral web connecting the ends of the guard surface at the back of said holder.

11. In a lock stitch sewing machine, an axially hollow rotary hook with an internal circumferential bearing shoulder; and anon-rotatinghollow bobbin holder with a segmental face flange at the front, and a cylindric body with a medial circumferentialexternal shoulder with an interruption at its top for thread clearance adapted to engage the shoulder of the rotary hook, said body having a sector forward of its shoulder which is circumferentially open except for relatively narrow connecting webs respectively at the top in the region of the interruption in the shoulder and at the ends of the face flange, and a.

rounded segment rearward of its shoulder which provides a guard surface for directing the needle thread loop around the back of the holder, the length of the latter segment being limited to the distance between the point of contact and the point of release of the loop.

12. In a lock stitch sewing machine, an axially hollow rotary hook with an internal circumfer- 'ential bearing shoulder; a latchless bobbin case of cup-shaped configuration with a front face of open spider formation; and an axially free hollow holder for the bobbin case having an open cylindric body with a segmental flange at the front, and a medial external circumferential shoulder with an interruption at the top for clearing the needle thread loop, adapted to bear against the internal shoulder of the hook, said body having a sector forward of the shoulder which is circumferentially open except for'relatively narrow connecting webs respectively at the top in the region of the interruption in the shoulder and at opposite ends of the faceflange, and a rounded segment rearward of said shoulder which providesa guard surface for directing the needle thread loop around the back of the holder, the length of the latter segment being limited to a distance between the point of contact and the point of release of the loop; and extraneous means for retaining the bobbin case within the holder.

13. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating hollow bobbin case holder retained within and by the rotary hook with capacity for limited axial play; opposing circumferential shoulders respectively on said hook and said holder; a bobbin case fitting within the holder; and, a separate retractable keeper means for maintaining the bobbin case in the holder with thecircumferential shoulder of the latter normally out .of contact with the circumferential shoulder. of the hook.

14. III a lock stitch sewing machine, an axially hollow. rotary hook; at non-rotating hollow bobbin case holder retained within and by the rotary hook with capacity for limited axial play;

opposing circumferential shoulders respectively on said hook and said holder; a bobbin case fitting within the holder; and separate pivotally supported retractable means to retain the bobbin case in the holder with the circumferential shoulder of said holder normally out of contact with the circumferential shoulder of the rotary hook.

15. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating axially? free hollow bobbin case holder within the rotary hook; opposing circumferential shoulders respectively on said hook and said holder; a bobbin case fitting withinthe holder; a keeper plate with spot projections at circumferential intervals between which and the exposed ends of the holder and the bobbin case the needle thread passes, whereby said bobbin case is retained in the holder with the circumferential shoulder of the latter normally out of contact with the circumferential shoulder of the rotary hook; and means for supporting the keeper'plate with capacity for adjustment in the direction of the hook arms.

16. In a lock stitch sewing machine, an axially hollow rotary hook; a non-rotating axially-free hollow bobbin case holder within the rotary hook; opposing circumferential shoulders respectively on said hook and said holder; 9.

bobbin case fitting within the holder; a keeper plate with spot projections at circumferentialintervals between which and the exposed endsof the bobbin case and the holder, the needle thread passes, whereby said bobbin case is retained in the holder with the circumferential shoulder of the latter normally out of contact with the circumferential shoulder of the rotary hook; and an arm supporting said plate with capacity for being swung to a retracted position for access to the bobbin case.

17. In a lock stitch sewing machine, an axially hollow rotary hook of open construction; an axbobbin case within said holder.

18. In a lock stitch sewing machine, an axially hollow rotary hook; an axially-free non-rotating bobbin case holder with a circumferential rib medially of its body for engaging an internal circumferential shoulder in the hook, said holder having a face flange with a rotation restraining notch at the top and a rounded projecting surface at the front at one side of the notch for controlling the bobbin thread; and a bobbin case within the holder.

19. In a lock stitch sewing machine, an axially hollow rotary hook with a circumferential internal groove; a non-rotating bobbin case holder; a bobbin case retained byand, mounted within the holder, said holder having a circumferential rib narrower than the groove of the hook; a latchless bobbin case fitting within the holder, said case being of cup shaped cross section and having an exposed end of open spider construccase for maintaining the latter within the holder with the rib of said holder at all times out of bearing contact with the outer side of the groove oi the hook, and normally out of contact with the inner side of said groove.

20. In a lockstitch sewing machine, an axially hollow rotary hook" with an internal groove, a

non-rotating bobbin case holder; a bobbin case within the holder, said holder having a circumferential rib narrower than the groove oi the hook; a latchless bobbin case fitting within the holder, said case being of cup shaped cross section and having an exposed end of open spoked construction; and a keeper with a spot projection corresponding in position to one of the spokes oi the bobbin case between which and said spokes the needle thread passes, whereby the case is retained within the holder with the rib of said holder at all times out of contact with the outer side of the groove of the hook, and normally out contact with the inner side of said groove.

21. A bobbin holder for use in tionewith as the rotary hook of a lock stitch sewing machine,

having a circumferential rib, a rearwardly-extending thread guiding surface operative to cast one limb of the needle loop over the back of the bobbin holder and extending circumferentially only from the point of initial contact of the needle loop to the point'of release of said loop, and a frontal segmental thread guarding flange connected at spaced points to the rib by circumierentially-narrow connecting webs.

22. A bobbin holder for use in association with the rotary hook for a lock stitch sewing machine, having a circumferential rib, a concentric segmental thread guiding surface operative to cast one limb of the needle loop over the back of the bobbin holder and extending circumfsrentially only from the point of initial contact of the needle loop to the point of .alease of said loop, and a frontal segmental thread guarding I e connected at its ends and at an intermediate point to thebsrib by circumferentially-narrow connecting we 28. In loop-taking mechanism for sewing Inachines, a rotary loop-seizing component; a nonrotating component disposed, with capacity for axial play, within the rotary component; a retractable member engaging the non-rotating componentandlimitingitsaxialplaysothatthe two components are normally out of axial contact; and additional means for holding the nonrotating component assembled with the rotating component upon retraction of said member;

24. In loop-taking m for sewing machines, a rotary loop-seizing component; a nonrotating component disposed, with capacity for axial play, within the rotary component; a member en aging the non-rotating component and limiting its axial play so that the two components are normally out of axial contact; a support for the member; and means whereby the member maybeadiustedonitssupporttovaryitslimiting eiiect upon the non-rotating t.

2B. In loop-taking mechanism for sewing ma chines, a rotary loop-seizing component; a nonrotating t disposed with capacity for axial play. within the rotary component; a member engaging the non-rotating component and limitingitsaxialplaysothatthetwoccmponsnts are normally out 0! axial contact: a retractable support for the member; medns whereby the member may be adiustedon its support to vary its limiting time upon the non-rotating component; and additional means for holding the non-rotating component assembled with the rotating component upon retraction of said mT iI-I 26. In a lock stitch sewing machine, stitchforming means including a rotating and a nonrotating component one having a circumferential groove and the other having a narrower interengaging rib permitting axial play-between said components; and means for determining a normal position for said components such that the opposite sides of the rib on the one-are out of contact with the contiguous sides of the groove in the other, and which upon passage of the needle thread between" it and component wherewith it normally contacts causes shifting of such component so that the rib bears lightly against one side of the groove.

27. In a lock stitch sewing machine, stitchiorming means; including a rotating component with a circumferential shoulder; a non-rotating component having an opposing circumferental shoulder and means on the rotating component for retaining the non-rotating component with capacity for limited axial play: and an element for-determining a normal position tor the non-rotating component such that its shoulder is out of bearing contact with the shoulder of the rotating component.

28. In a lock stitch sewing machine, stitchforming means including a rotating needle loop seizing component with a circumferential shoulder; a non-rotating component about which the needle loop is passed, having an opposing circumferential shoulder; means on the rotating component for retaining the non rotating component with capacity for limited axial play; and an element with a spot projection, between which and the non-rotating component the outer limb of the needle loop is adapted to pass, said clement determining a normal position for said non-rotating component such that its shoulder is clear of the shoulder of the rotating component by an interval corresponding substantially to the thickness of the needle thread.

29. In a lock stitch sewing machine, stitchforming mechanism including a rotating component with a circumferential shoulder; a nonrotating component with a circumferential rib which is interrupted to provide a needle loop detaining horn; and a member for limiting outward axialplay of the non-rotating component so that its rib is normally out of contact with the circumf'erential shoulder of the rotating component, said member having a spot projection between which and the non-rotating component one limb of the needle loop is adapted to pass, said projection lying substantially in a planewhich is radial to the axis oh the rotating component and which extends through the end of the loop detaining horn.

30. In a lock stitch sewing machine, stitchforming mechanism including a rotating com-- ponent witha circumferential shoulder; a nonrotating component with a circumferential rib which is interrupted to provide a needle loop detaining horn; and a, member for limiting outward axial play of the non-rotatingjcomponent so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having a plurality of spaced spot projections between which and the non-rotating component one limb of. the needle loop is adapted topass,oneotsaidspctproiectionslyingsubstantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

31. In a lock stitch sewing machine, stitchforming mechanism including a rotating component with a circumferential shoulder; a nonrotating component with a circumferential rib which is interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having two spaced spot projections between which and the non-rotating component one limb of the needle loop is adapted to pass, one of said spot projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

32. In a lock stitch .sewing machine, stitchforming mechanism including a rotating component with a circumferential shoulder; a nonrotating component with a circumferential rib which is interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having a spot projection eccentric to the axis of the rotating component and located in a plane above said axis at the downwardly moving side of said ro-v tating component as considered with regard to its normal rotation, between which projection .and the non-rotating component one limb of the needle loop is adapted to pass.

33. In a lock stitch sewing machine, stitchforming mechanism including a rotating component with an internal circumferential'groove; a non-rotating component with an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that the rib of the latter is normally out of contact with both sides of the groove in the rotating component, said member having a spot projection between which and the non-rotating component one limb of the needle loop is adapted to pass, said' projection lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

34. In a lock stitch sewing machine, stitchforming mechanism including a rotating component with an internal circumferential groove; a non-rotating component with an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that the rib'of the latter is normally out of contact with both sides of the groove in the rotating component, said member having a plurality of spaced spot projections between which and the non-rotating component, one limb of the needle loop is adapted to pass, one of said spot projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop' detaining horn.

35. In a lock stitch sewing machine, stitchformlng mechanism including a rotating com- 'ponent with an internal circumferential groove:

a non-rotating component with an external circumferential rib engaging the-groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that the rib of the latter is normally out of contact with both sides of the groove in the rotating component, said member having two spaced spot projections between which and the non-rotating component, one limb oi the needle loop is adapted to pass, one of said spot projections lying substantially in a plane which is radial to the axis of the rotating component, and which extends through the end of the loop detaining horn.

36. In a lock stitch sewing machine, stitchforming mechanism including a rotating component with an internal groove; a non-rotaating component "with an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that the rib of the latter is normally out of contact with both sides of the groove in the ro tating component, said member having a spot projection eccentric to the axis of the rotating component and located in a plane above said axis at the downwardly moving side of said rotating component as considered with regard to its normal rotation,'between which projection and the non-rotating component, one limb of the needle loop is adapted to pass.

37. In a lock stitch sewing machine, stitchforming mechanism including a rotary hook with an internal circumferential groove; a non-rotating bobbin case holder with an external circumferential rib engaging the groove of the rotary hook, said rib being narrower than the groove and being interruptedto provide a needle loop detaining horn; a bobbin case within the holder; and a keeper for limiting outward axial play of the bobbin case holder so that the rib of the latter is normally out of contact with both sides of the groove in the rotary hook, said keeper having a spot projection between which and the front of the bobbin case, one limb of the needle loop is adapted to pass, said projection lying substantially in a plane which is radial to the hook axis and which extends through the end of the loop detaining horn.-

38. In a lock stitch sewing machine, astitchforming mechanism including a rotary hook withan internal circumferential groove; a non-rotating bobbin case holder with an external circumferential rib engaging the groove of the rotary hook, said rib being narrower than the groove and being interrupted to provide a needle.

loop detaining born; a bobbin case within the holder; and a keeper for limiting outward axial keeper having a plurality of spaced spot projections between which and the front of the bobbin case, one limb of the needle loop is adapted to pass, and one of said spot projections lying substantially in a plane which is radial to the axis of the rotary hook and which extends through the end of the loop detaining horn.

39. In a lock stitch sewing machine, ltikh.

forming mechanism including a rotary hook with aninternal circumferential groove; a non-rotating bobbin case holder with an external circumferential rib engaging the groove of the rotary hook, said rib being narrower than the groove and being interrupted to provide a needle loop detaining born; a bobbin case within the holder; and a keeper for limiting outward axial playof the bobbin case holder so that the rib of the latter is normally'out of contant with both sides of the groove in the rotary hook, said keeper having two spaced spot projections between which and the front of the bobbin case, one limb of the needle loop' is adapted to pass, one of said spot projectionslying substantially in a plane which is radial to the axis of the rotary hook" and which extends through the end of the loop detaining horn.

40. In a lock stitch sewing machine, stitchforming mechanism including a rotary hook with an internal circumferential groove; a nonrotating bobbin case holder with an external circumferential rib engaging the groove of the ro-' tary hook, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; a bobbin case within the holder; and a keeper for limiting outward axial play of the bobbin case holder so that the rib of the latter is normally out of contact with both sides of the groove in the rotary hook, said keeper having a spot projection eccentric to the axis of the rotary hook and located in a plane above said axis at the downwardly moving side of the said hook as considered with regard to'its normal rotation, between which projection and the bobbin case one limb of the needle 1001i is adapted to pass.

41. In a lock stitch sewing machine, a reciprocating needle; means including a rotating component which is adapted to revolve twice for each reciprocation of the needle, and which has a circumferential shoulder, and a non-rotating component with a circumferential rib which is interrupted to. provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having a spot projection between which and the nonrotating component, one limb of the needle'loop is adapted to pass, said projection lying substantially in a plane which is radial to the. axis of the rotating component and which extends through the end of the loop detaining horn. V

42. In a lock stitch sewing machine, a reciprocating needle; complemental stitch-forming means including a rotating component which is adapted to revolve twice for each reciprocation of the needle and which has an internal circumferential groove, and a non-rotating'component with an external circumferential rib enga in the groove of the rotating component, said rib being narrower than the groove and being interruptedto provide a needle loop detaining horn;

and a member for limiting outward axial play of the non-rotating component so that the rib of the latter is normally out of contact with-both sides of the groove in the rotating component,

complemental stitch-forming said member having a spot projection between which and the non-rotating component one limb of the needle loop is adapted to pass, said projection lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

43. In a lock stitch sewing machine, a'reciprocating needle; 'ccmplemental stitch-forming means including a rotary hook which is adapted to revolve twice for each reciprocation of the needle and which has'an internal circumferential groove; a non-rotating bobbin case holder with an external circumferential rib engaging the groove of the rotary hook, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn, and a bobbin case within the holder; and a keeper for limiting outward axial play of the bobbin case holder so that the rib of the latter is normally out of contact with both sides of the groove in the rotary hook, said keeper having a spot pro- 'iection between which and the front of the bob his case one limb of the needle loop is adapted to pass, said projection lying substantially in a plane which is radial to the hook axis and which extends through the end of the loop detaining horn.

44. In a lock stitch sewing machine, stitchforming mechanism including a rotating component and a non-rotating component retained within the rotating component with capacity for limited axial play; opposing circumferential shoulders respectively on said components; and separate means for controlling the non-rotating component to keep the shoulder thereof normally out of contact with the shoulderof the rotating" component.

45. m a lock stitch sewing machine,'stitchforming mechanism including a pair of relatively rotating components, one retained within the other with capacity for limited axial movement; opposing circumferential shoulders on said components; and separate means for controlling'one I of said components to keep the shoulder thereof normally out of contact with the shoulder of the other component. 4

46. In a lock stitch sewing machine, a needle; and complemental stitch-forming means including a pair of relatively rotating components, one within the other, said components having opposing circumferential shoulders,' and the inner component having a rounded cylindric segment rearward of the plane of its shoulder providing a deflecting surface for directing the needle thread loop around the back of sald inner com ponent.

47. In a lock stitch sewing machine, stitchforming mechanism including a rotating component and a non-rotating component interengaged for maintenance in assembly and having capacity for limited relative axial play normally; and control means insuring by coaction with the needle thread during each stitch-forming cycle, the reduction and substantial taking up of the axial play between said components.

cnsnms F.,RUBEL. cmnmvcn c. sun-n.