US3194197A - Chain sitch device for lock stitch sewing machines - Google Patents

Description

July 13, 19 5 a J. KETTERER ETAL 3,194,197

CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES Filed Aug. 7, 1963 4 Sheets-Sheet 1 mvewrons Stanley .1 Ire/feral,

Mic/Mel F. Ivan/m,

W/7/Iam B. Sim/l, 001/ By Joseph J. Home WITNESS Fi 43.

v Mad-0% g ATTORNEY July 13, 1965 s. J. KETTERER ETAL 3,194,197

CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES Filed Aug. 7, 1963 4 Sheets-Sheet 2 uv VENTORS. Stanley J Kalle/er, MIcfiae/E Ivan/m WIYI/bm B. Sim/l, andJosep/z J Dal/1e} WI TN E53 BY 4 5 f C 5 ATT RNEY July 13, 1965 s. J. KETTERER ETAL 3,194,197

CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES 4 Sheets-Sheet 3 Filed Aug. '7, 1963 Fig. I0

IN VE N TORS Fig.9

4/. m n N w m 30 T m N WW8 0% k y m KMU J W/ lP-B 00 mm I M WITNESS d/MW 9 y 1965 s. J. KETTERER ETAL 3, 4, 7

CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES Filed Aug. '7, 1965 4 Sheets-Sheet 4 mvmrans. Stanley J Ke/ferer Mic/Joell? mum/121 50. Sim/f,

BY and Joseph J Dolney. WITNESS AT TORNEY United States Patent 3,.l94,l 7 CHAIN STITCH DEVI CE 1 9B; LGCK STITCH SEWENG MACHINE Stanley J. Ketterer, Morris Plains, Michael F. Ivanho, Rockaway, Joseph .I. Dolney, Denville, and William 1%. Strait, East Paterson, Nah, assignors to The Singer Company, Elizabeth, N..I., a corporation of New .lersey Filed Aug. 7, 1963, Ser. No. Eitltlflfitl 9 Ciairns. (6i. 112-162) This invention relates to sewing machines, and more particularly to devices for converting a lock stitch sewing machine into a chain stitch sewing machine.

It is an object of this invention to provide devices attachable to a lock stitch sewing machine for converting the machine to chain stitch formation.

A further object of this invention is to provide a simple and effective chain stitch conversion device for a lock stitch sewing machine operative to efiect a positive control over manipulation of the sewing thread during concatenation into chain stitches.

Another object of this invention is to provide a readily interchangeable conversion device assoicated with the needle thread take-up mechanism of the sewing machine for converting the needle thread take-up action from one tailored for lock stitch formation to one particularly suitable for chain stitch formation.

Still another object of this invention is to provide chain stitch conversion devices of the above character which operate advantageously in combination with stitch-bystitch bobbin thread pull-off devices of a lock stitch sewing machine.

The accompanying drawings illustrate a preferred embodiment of this invention in which:

FIG. 1 represents a head end elevational view of a sewing machine having chain stitch conversion devices in accordance with this invention applied thereto and with the bracket arm end cover plate and the bed broken away to expose the mechanism therein.

FIG. 2 represents a side elevational view of a portion of the bracket arm of the sewing machine of FIG. 1.

FIG. 3 is a perspective view of a portion of the stitch forming instrumentalities with the chain stitch conversion devices of FIG. 1, showing the disposition of parts and thread as the needle penetrates the work.

FIG. 3A is a cross-sectional view of the stitch forming instrumentalities taken substantially along line 3A-3A of FIG. 3.

FIG. 4 is a perspective view of the stitch forming instrumentalities similar to that of FIG. 3 but showing the disposition of parts and thread as the needle emerges from the work after loop seizure.

FIG. 4A is a cross-sectional view of the stitch forming instrumentalities taken substantially along line 4A-4A of FIG. 4.

FIG. 5 is a perspective view of the stitch forming instrumentalities similar to that of FIG. 3 but showing the disposition of parts and thread as the needle reaches substantially the top of its stroke.

FIG. 5A is a cross-sectional view of the stitch forming iustrumentalities taken substantially along line SA-SA of FIG. 5.

FIGS. 6 and 7 illustrate a modified form of the chain stitch fittings of this invention in which:

FIG. 6 is a front elevational view of a throat plate suitable for use with a sewing machine illustrated in FIG. 1 but including a modified form of chain stitch thread loop supporting finger carried on the throat plate, and

FIG. 7 is an enlarged vertical cross-sectional view through the axis of the sewing machine needle similar to that illustrated in FIG. 1 but showing the modified form of chain stitch loop supporting finger of FIG. 6.

FIGS. 8, 9 and 10 illustrate another modified form of the chain stitch fittings of this invention in which:

for use with the loop taker of the sewing machine illustrated in FIG. 1 and having a modified form of the chain stitch conversion fittings of this invention applied thereto,

FIG. 9 is a bottom plan view of a throat plate for the sewing machine of FIG. 1 with a chain stitch thread loop supporting finger complemental to the fittings on the bobbin case illustrated in FIG. 8 applied thereto, and

FIG. 10 is a perspective view of the complemental chain stitch conversion fittings of FIGS. 8 and 9 detached from the bobbin case and throat plate, respectively.

FIGS. 11, 12 and 13 illustrate two ways in which the action of the needle thread take-up mechanism of a lock stitch sewing machine may be modified in a manner favorable to chain stitch formation and in which:

FIG. 11 is a perspective view of the stitch forming instrurnentalities of the sewing machine of FIG. 1 illustrating the manner in which the thread is influenced by an auxiliary chain stitch thread guide associated with the needle thread take-up mechanism,

FIG. 12 is a perspective view of a portion of the stitch forming instrumentalities illustrated in FIGS. 1, 3, 4 and 5 with a modified form of chain stitching insert for the bobbin case and illustrating the manner in which the thread is influenced thereby, and

FIG. 13 is a cross-sectional view taken substantially along line 10-10 of either FIG. 11 or FIG. 12 illustrating the manner in which the chain stitches are set.

This invention provides for the conversion to single thread chain stitch sewing of a conventional lock stitch sewing machine. FIG. 1 illustrates a head end elevational view of a household lock stitch sewing machine built in accordance with the co-pending US. application of S. I. Ketterer, Serial No. 133,896, filed August 25, 1961, to which this invention may be applied.

The. sewing machine frame includes a bed 11 from which rises a standard 12 supporting a bracket arm 13 overhanging the bed. A main shaft 14 journaled lengthwise in the bracket arm drives all of the moving parts of the sewing machine and may be actuated by an electric motor (not shown), by foot treadle or the like.

A counterbalanced crank 15 on the main shaft 14 is operatively connected by means of a drive link 16 to a needle bar 17 endwise slidable in a bearing 18 in the bracket arm and carrying at its lower extremity an eye pointed needle 19. The crank 15 also actuates a needle thread take-up lever 24) of which the motion is constrained by an anchor link 21. The usual path of a needle thread during the formation of lock stitches passes from a supply (not shown) to a thread tensioning device 22, through an eyelet 23 in the take up lever 20, and then through a thread guide 24 and to the needle eye. This needle thread control arrangement is typical of that which is required for lock stitch formation. The use of the chain stitch conversion devices of this invention will operate success,- fully with such lock stitch type needle thread controls however, this invention includes means as will be de scribed later for modifying the lock stitch needle thread control to obtain a condition more suitable for chain stitch formation.

Iournaled in the bed on a loop taker shaft 30 is a loop taker indicated generally at 31. The loop taker illustrated in the drawings is a vertical axis rotary hook adapted to partake of two revolutions for each reciprocation of the needle. The loop taker is formed with a cup shaped body portion 32 formed with an inwardly extending loop seizing beak 33 adapted to engage and manipulate loops of thread from the needle 19 which, as: illustrated adapted to accommodate one flange of a thread carrying bobbin (not shown) which is used when lock stitches are to be formed. The bobbin case also includes a pivoted arm 39 formed with a spherical protuberance 39' adapted to engage and center a bobbin in the bobbin case.

The needle and loop taker thus far described are capable of producing lock stitches in a conventional manner. The loop seizing beak 33 of the loop taker will engage and carry loops of needle thread completely about the bobbin case and thus if a threaded bobbin is in place in the bobbin case, the needle and bobbin threads will be concatinated into true lock stitches (Federal type #301) following each needle penetration. The loop taker may be driven at two revolutions for each needle reciprocation by means of a shaft 40 in the standard 12 driven by bevel gears 41 from the main shaft and connected in turn by bevel gears 42 to a bed shaft 43 which drives the loop taker shaft 3% by a set of bevel gears 4-4.

Illustrated in FIG. 1 is a work feeding mechanism of the four-motion or drop feed variety. A work engaging feed dog operating through slots 51 in a throat plate 52 on the bed is secured by screws 53 to a feed bar 54 beneath the bed. Feed advance and return movements are imparted to the feed bar from an oscillating feed advance rock shaft 55 connected to the feed bar by means of a rock arm 56. The feed advance rock shaft 55 is oscillated by means of conventional connections 57 in the standard from a feed cam 58 on the main shaft 14. The connections 57 may include conventional regulating means 59 for varying the stitch length. Rising and falling motion is imparted to the feed bar from an oscillating feed lift rock shaft 60 in the bed. The feed lift rock shaft 60 is provided with a rock arm 61 connected by means of a link 62 to the feed bar 54. The feed lift rock shaft is oscillated by means of conventional connections 63 in the standard from a feed lift eccentric 64 on the main shaft 14. It will be appreciated that, as is conventional in the art, the work feeding mechanism is timed relatively to the needle reciprocation so that the feed dog is lifted and advanced while the needle is raised out of any work on the throat plate, and the feed dog is lowered beneath the throat'plate and returned while the needle descends.

Carried and actuated by the work feed mechanism of the sewing machine is a stitch-by-stitch bobbin thread pull-off device which is described in detail in the copending US. application of S. J. Ketterer, Serial No. 280,281, filed May 14, 1963. The pull-off member 65 includes a bifurcated portion 66 which embraces the pivotal connection between the feed advance rock arm 55 and the feed bar 54. The pull-off member is also constrained between the feed dog 50 and the feed bar 54 so as to partake of the rising and falling movements of the feed bar. A depending arm 67 on the pull-off member 65 is connected by means of a link 68 to a rock arm 69 fast on the feed lift rock shaft 60 so as to impart to the pull-off member 65 advance and return movements parallel to but in different direction from that of the feed bar 54. In general, on the downstroke of the feed dog at the completion of each feed motion, the pullolf member, in addition to being dropped with the feed bar, will be imparted a rearward motion relatively to the feed bar. Beneath the feed dog, the pull-off member 65 is formed with an aperture 70 which accommodates endwise reciprocation of the needle. A rib 71 at the forward extremity of the pull-off member 65 and across the aperture 70 thereof thus overlies any needle thread loop which may be seized and manipulated by the loop taker beak 33.

The fittings necessary to convert the conventional lock stitch sewing machine illustrated in FIG. 1 into a readiness for chain stitching comprise generally a member carried relatively to the machine frame and a co-operatiug member carried relatively to the loop taker bobbin case. Three forms of such chain stitch conversion fittings are illustrated in the drawings; one form being illustrated in FIGS. 1, 3, 4 and 5, a second form in FIGS. 6 and 7, and a third form in FIGS. 8, 9 and 10.

Referring to FIGS. 1, 3, 4 and 5, and the supplemental FIGS 3A, 4A and 5A, a member 89 illustrated in the entirety in FIG. 4 is freely pivoted beneath the sewing machine throat plate 52. The member includes a boss 81 apertured as at 82 to accommodate a fulcrum rivet 83 by which the member 7 9 is pivoted to the throat plate. An arm 84 extends from the base 81 across throat plate in front of a needle aperture 85 therein and substantially at right angles to the feed dog slots 51 in the throat plate. The arm 34 in front of the needle aperture is formed with a downturned chain stitch thread loop supporting finger 85 extending substantially parallel to the path of reciprocation of the needle. The finger 86 is formed with a vertically elongate aperture 37 extending substantially parallel to the line of work feed. The extremity of the arm 84 opposite the boss 81 is formed with a downturned lip 88 disposed in alignment with one of the feed dog slots 51 in the throat plate. The thread loop supporting finger 86 is thus carried for swinging movement in an arc of which the chord extends substan-tially along the line of work feed of the work feeding mechanism.

Co-operating with the thread loop supporting finger 86 is a thread directing member 94) which is carried the bobbin case 34. Referring to FIGS. 1 and 3, the thread directing member 90 comprises a generally flat plate 91 shaped to be accommodated in the annular seat .38 of the bobbin case in place of the top flanges of a thread carrying bobbin. The plate 91 is formed with a central aperture 92 adapted to accommodate the protuberance 39 of the hinged arm 39 which holds the plate 91 down on the bobbin case. The plate 91 is formed with spaced radial notches 93, 94 defining a central projection which may be offset upwardly as illustrated in FIG. 3 and is formed with a tapered free extremity 96. The projection 95 is flanked at each side by arms 97 and 98 defined by the notches 93 and 94- and each of the arms 97 and 98 preferably extends outwardly beyond the annular seat 38 of the bobbin case so as to prevent rotation of the member 98 relatively to the bobbin case. The free extremity 96 of the projection 95 is arranged in alignment with the aperture 87 of the thread loop supporting finger 86 so that as the member 80 swings clockwise as viewed in FIG. 3, the aperture 87 will embrace the free extremity 96 of the projection 95 and as the member 30 swings clockwise as viewed in FIG. 3, the thread supporting finger 86 will move to a position completely beyond and out of embracing re lationship with the projection 95.

The operation of the sewing machine with the chain stitch fittings 80 and 90 of FIGS. 1, 3, 4 and 5 may be explained with reference to FIGS. 3, 4 and 5 taken together with FIGURES 3A, 4A and 5A. In these figures, the thread is illustrated as it will occur in the various phases of a chain stitch forming cycle when the needle thread is directed to the take up as described above in the conventional fashion for sewing lock stitches; that is, from the tension device 22 to the take up eyelet 23, the guide 24 and thence to the needle.

FIGS. 3 and 3A illustrate the position of the parts and thread as the needle penetrates the work. The feed dog 50 is at the completion of its feed advance stroke and is beginning to be lowered, the pull-off member 6.5

is substantially at the forward most and highest position and is beginning to be lowered with the feed dog and beginning to be shifted toward the left as viewed in FIG. 3A. The web 71 of the pull-oft" member 65 however, bears against and constrains the thread loop supporting finger 36 in a position in which the aperture 87 embraces the extremity 96 of the projection 95. The previous loop of needle thread seized and manipulated by the beak 33 of the loop taker will therefore be trapped by the interengaged elements 86, 96 so that the previous thread loop will draw snugly about the thread loop supporting finger 86 and will not slip downwardly and olf the finger. The needle 19 will therefore penetrate the previous thread loop detained about the finger 86 and thus form a chain by carrying a new loop of needle thread through the previous loop.

FIGS. 4 and 4A illustrate the position of the parts and of the thread as the needle rises out of the work following loop seizure by the beak 33 of the loop taker 31. The feed dog 50 will be lowered and partaking of its return stroke. The pull-oft member 65 will similarly be in its lowest position and also will have moved to the left as viewed in FIG. 4A freeing the thread loop supporting finger 86 of constraint and allowing it to move in response to tension in the previous thread loop away from the free extremity 96 of the projection 95. The Web 71 of the pull-01f member 65 in moving downwardly will strip the previous thread loop downwardly and off the thread loop supporting finger. The web 71 of the pull-off member 65 acts in chain stitching with the conversion devices of this invention, as a thread stripping element for forcing the thread loop from the thread loop supporter finger 86.

FIGS. 5 and 5A illustrate the position of the parts and of the thread as the needle approaches the top of its stroke. The feed dog 5% on being moved to the right to begin a new feed advance stroke will engage the lip 88 on the member 80 turning the member 89 about its pivotal connection with the throat plate and bringing the aperture 87 in the thread loop supporting finger 86 into embracing relation with the extremity 96 of the projection 95 of the thread directing member 90. As the newly seized thread loop is cast from the loop taker beak 33, therefore, the interengaged elements 86, 96 trap the loop and prevent it from dropping from the thread loop supporting finger 86. The projection 95 then directs the trapped loop onto the loop supporting finger 86. The action of the loop taker beak 33 in manipulating the newly seized thread loop will draw some but not all of the slack from the thread loop previously released from the thread loop supporting finger 86. In substantially the position of parts illustrated in FIGS. 5 and 5A, the needle thread take up 20 will next draw up the thread pulling the new thread loop snugly onto the thread supporting finger 86 and drawing the previous thread loop tightly against the underside of the work. As the needle moves from the raised position of FIGS. 5 and 5A to the lowered position of FIGS. 3 and 3A, the feed dog will move to the left on its feed advance stroke, but the web 71 of the pull-oil? member will remain adjacent to the thread loop supporting finger 86 constraining the finger in a position embracing the projection 95 so as to prevent inadvertent slippage of the thread loop from the finger 86.

The conversion from readiness to sew lock stitches to readiness to sew chain stitches using the fittings above described requires that an operator exchange a conven-- ftional bobbin in the bobbin case for a member 90 therein and that she exchange a conventional throat plate for a throat plate having a member 89 pivoted therebeneath.

The modified form of fittings illustrated in FIGS. 6 and 7 utilizes precisely the same thread directing member 90 as is used in the embodiment of FIGS. 1, 3, 4 and 5. In the embodiment of FIGS. 6 and 7, however, a thread loop supporting member 189 is loosely pivoted to the throat plate 52 by a fulcrum rivet 131 together with a leaf spring 182 formed with downturned ears 183 embracing the thread loop supporting member. The thread loop supporting member 189 is formed with a loop supporting finger 136 apertured at 187 as in the previously described version. However, the leaf spring 182 which bears against the underside of the throat plate biases the loop supporting finger 186 downwardly so that despite variations in dimensions of throat plate thickness, loop taker elevation and the like, the loop supporting finger 186 will extend downwardly sufiiciently to engage the needle thread loops, while if the combination of dimensions of a particular sewing machine should be such that the finger 186 engages the bobbin case, the spring 182 provides for yielding without damage to the parts. The thread loop supporting member 180 is formed with a downwardly offset projection 183 in alignment with the feed dog 50 in place of the lip 88 of the previously described version and with an attenuated free extremity 189 for the purpose of preventing thread loops from catching thereon.

FIGS. 8, 9 and 10 illustrates a modified form of the chain stitch fittings of this invention in which the fittings are adapted to be used with a slightly different type of lock stitch forming mechanism than that illustrated in the other figures. In FIGS. 8, 9 and 10, the fittings are adapted for use with a sewing machine as described in detail in the US. patent of R. E. Johnson, No. 2,966,130, December 27, 1960, which employs a bobbin case 234 adapted to be journaled in the sewing machine loop taker and constrained against rotation therewith. The bobbin case 23 is formed with a cavity 235 adapted to accommodate a thread carrying bobbin (not shown) and since the bobbin cavity occupies a relatively small space on the bobbin case a considerable shelf 236 is provided thereon.

The fittings illustrated in FIGS. 8, 9 and 10 include a member 286 freely pivoted beneath the throat plate 52 and for this purpose including a boss 281 apertured at 282 to accommodate a fulcrum pin 283 on the throat plate on which the member 23% is constrained by a spring clip 284. An arm 285 extends from the boss 281 and is formed with a downturned thread loop supporting finger 286 in which a vertically elongate aperture 287 is formed. The arm 285 is also formed with a downturned lip 238 disposed in alignment with one of the feed dog slots 51 in the throat plate. As illustrated in FIG. 9, the throat plate 52 may also be formed immediately forwardly of the needle aperture with a depending projection 289 which serves to spread the loop of thread on the thread loop supporting finger 236 for penetration thereof by the needle.

As illustrated in FIG. 8, a sheet metal bracket 290 is fixedly secured as by welding to the shelf 236 on the bobbin case 234. At one side the bracket 290 is formed with an upstanding fin 291 formed with a projection 292 which tco-operates with and is embraced by the aperture 237 in the thread loop supporting finger 286 of the member 28-3 :and the throat plate. At the other side, the bracket 299 is formed with an upstanding fin 293 tapered as at 294 to deflect thread loops over the fin 291 and onto the thread loop supporting finger 236 of the member 289.

The modified form of fittings illustrated in FIGS. 8, 9 :and 10 operate in the same fashion to form chain stitches as do the fittings of FIGS. 1, 3, 4 and 5. In the conversion of a sewing machine from lock stitching to chain stitching however, only the throat plate need he changed. The bobbin case 23 3 with the bracket 2% attached will serve in the absence of a to sew lock stitches.

When fitted to sew chain stitches, a sewing machine equipped with the fittings illustrated in FIGS. 8, 9 and 10 may also be operated with a thread carryingbobbin in place in the cavity 235 of the bobbin case. A bobbin thread when incorporated in a chain stitch seam will not bedrawn tightly into the stitches .as it is in a lock stitch seam, but will lie on the underside of the Work in loose eoncantenation with the chain stitch loops. The bobbin member 28% on the throat plate arcane? when in place will lock the chain stitch seam and prevent raveling. The bobbin thread may be cut and withdrawn from the seam readily however, leaving a plain single thread chain stitch seam which may be unraveled easily and quickly.

The modifications illustrated in FIGS. 11, 12 and 13 are concerned with means for imparting tension control on the thread while sewing chain stitches to provide for setting of the chain stitches at a more advantageous time during each cycle of chain stitch formation.

In the modification illustrated in FIG. 11, the chain stitch conversion fittings 89 on the throat plate and he on the bobbin case are identical to those illustrated in FIGS. 1, 3, 4 and 5. In the operation of these fittings as described With reference to FIGS. 3, 4 and 5, the setting of each stitch occurs at the top of the needle stroke and after the parts and threads have assumed the position illustrated in FIGS. 5 and SA since in FIGS. 3, 4 and 5, the path of the needle thread to the needle remains as in lock stitch formation. As a result, stitch setting occurs after each new thread loop is snubbed about the thread loop supporting finger 86. With reference to FIGS. 5 and 5A it will thus be apparent that to set the chain stitch using lock stitch type needle thread control, the thread tightened by the take up lever 20 must reeve about the thread loop supporting finger 86 and then back through the preceding stitch. A relatively high thread tension is thus required and the presence of loose thread loops in the system until such a late point in the stitching cycle gives rise to the possibility that the loops may catch or tangle inadvertently.

As illustrated in FIG. 11, an auxiliary thread guide 300 is secured on the bracket arm 13 of the sewing machine by fastening screw 301 so as to admit of limited adjustment alongside the path of movement of the needle thread take up lever 29. The thread from the take up eyelet 23 to the needle is then passed through the auxiliary thread guide 300 before passing through the thread guide 24. As a result, the thread capacity of the take up mechanism is reduced; that is, the difference between the maximum and minimum quantity of thread manipulated by the take up lever 20 is reduced. When the loop taker beak 33 engages and draws out the needle thread as illustrated in FIG. 11, the auxiliary thread guide 300 takes sufficient thread from the take up thread capacity so that the descending take up lever 29 cannot supply sufficient thread to satisfy the loop taker beak 33. This insufficiency, which may be regulated nicely by adjusting the position of the auxiliary thread guide 300, thus must be supplied from the previously held thread loop. In the version as illustrated in FIG. 11, the chain stitch is thus set by the loop taker during expansion of each new thread loop thereby as illustrated quasi-diagrammatically in FIG. 13. The modification illustrated in FIG. 11 thus sets each stitch almost 180 of arm shaft rotation ahead of the stitch setting point of the version illustrated in FIGS. 3, 4 and 5. As a result, the thread path at stitch setting is more direct and the thread tensions may thus be considerably lower. Also the absence of loose thread loops during a greater part of the stitching cycle reduces the possibility of inadvertent catching or entangling.

The modification illustrated in FIG. 12 utilizes the lock stitch type needle thread take up threading as described in connection with the operation of the version illustrated in FIGS. 3, 4 and 5; that is, the auxiliary thread guide 300 is not used with the version illustrated in FIG. 2. A similar result is obtained however, by virtue of an upturned thread camming surface 310 formed on the plate 391 of a thread directing member 390. In all other re spects, the thread directing member 390 is identical with the member 90 illustrated in FIGS. 1, 3, 4, 5 and 11, including a pair of notches 393-3fi4 defining a central projection 195 of which the extremity 3% co-operates with the thread loop supporting member 80. The notches 393 and 394 as before also define arms 397 and 393 for constraining the member 390 in place in the bobbin case 34- In the modification illustrated in FIG. 12, as the loop taker beak 33 expands each needle thread loop, the thread camming surface 310 enlarges that loop to such an extent as to exceed the quantity of thread being provided by the needle thread take up lever 20 and the necessary thread to make up for this insufficiency is taken from the loose previously held thread loop so that the chain stitches are set by the loop taker during expansion of each newly seized loop of needle thread.

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

1. In a sewing machine having lock stitch forming instrumentalities including a frame having a work support formed with a needle aperture, a thread carrying eyepointed needle supported above the work support for endwise reciprocation through said needle aperture, a circularly moving loop taker disposed below said work support, means for driving said needle and loop taker in timed relation for the seizure of a loop of thread from the eye of the needle by said loop taker during each stroke of the needle downwardly through said needle aperture and the release of said seized loop by the loop taker during each succeeding upward stroke of the needle, a needle thread take-up mechanism effective alternately to draw tight and to slacken said needle thread, a bobbin supporting case journaled in said loop taker, stop means sustained on said frame for constraining said bobbin supporting case from circular movement with said loop taker and, a linear work feeding mechanism effective to advance work fabric on said work support in one direction from said needle aperture between each needle penetration thereof, means for sewing chain stitches using thread carried by said needle comprising a thread loop engaging finger carried beneath said work support and having a free extremity extending in a direction away from said work support substantially parallel to said path of endwise needle reciprocation and arranged at that side of said path of needle reciprocation which is opposite the direction of advancement of work fabric by said work feeding mechanism, means shiftably supporting said thread loop engag ing finger relatively to said frame for movement substantially along the line of work feed of said work feeding mechanism, said thread loop engaging finger being formed with an opening extending substantially parallel to the line of Work feed of said Work feeding mechanism, thread directing means carried by said bobbin supporting case and formed with a projection adapted to be embraced by said opening in said thread loop engaging finger, means operated by said work feeding mechanism for shifting said thread loop engaging finger into embracing relationship with said projection during each release of said thread loop by said loop taker, a thread stripping element disposed between said thread loop engaging finger and the path of endwise reciprocation of said needle, and means for reciprocating said stripping element in timed relation with said endwise reciprocation of said needle and toward the free end of said thread loop engaging finger as said needle penetrates said needle aperture.

2. A device as set forth in claim 1 in which said thread directing means carried by said bobbin case and formed with a projection comprises a bracket rigidly secured to said bobbin case.

3. In a sewing machine having lock stitch forming instrumentalities including a frame having a work support, a removable throat plate carried on said work support and formed with a needle aperture, a bobbin supporting case journaled in said loop taker, stop means sustained on said frame for constraining said bobbin supporting case from circular movement with said loop taker and, a linear work feeding mechanism effective to advance work fabric on said work support in one direction from said needle aperture between each needle penetration thereof, means for sewing chain stitches using thread carried by said needle comprising a thread loop engaging finger carried beneath said work support and having a free extremity extending i 9 in a direction away from said work support substantially parallel to said path of endwise needle reciprocation and arranged at that side of said path of needle reciprocation which is opposite the direction of advancement of work fabric by said Work feeding mechanism, means pivotally supporting said thread loop engaging finger relatively to said sewing machine frame for movement in an arc of which the chord extends substantially along the line of Work feed of said work feeding mechanism, said thread loop engaging finger being formed with an opening extending substantially parallel to the line of work feed of said work feeding mechanism, thread directing means carried by said bobbin supporting case and formed with a projection adapted to be embraced by said opening in said thread loop engaging finger, means operated by said Work feeding mechanism for turning said thread loop engaging finger about said pivotal supporting means into embracing relationship with said projection during each release of said thread loop by said loop taker, a thread stripping element disposed between said thread loop engaging finger and the path of endwise reciprocation of said needle, and means for reciprocating said stripping element in timed relation with said endwise reciprocation of said needle and toward the free end of said thread loop engaging finger as said needle penetrates said needle aperture.

4. A device as set forth in claim 2 in which said thread loop engaging finger is pivotally supported on said removable throat plate.

5. A device as set forth in claim 2 in which said thread loop engaging finger is loosely pivoted relatively to said sewing machine frame and a spring means is interposed between said sewing machine frame and said thread loop engaging finger biasing said thread loop engaging finger away from said sewing machine frame.

6. In a sewing machine having lock stitch forming instrumentalities including, a frame having a work support formed with a needle aperture, a thread-carrying eyepointed needle supported above said work support for endwise reciprocation through said needle aperture, 21 circularly moving loop-taker disposed below said work support on an axis substantially parallel to the path of endwise reciprocation of said needle, and a bobbin supporting case journaled in said loop taker, stop means sustained on said frame for constraining said bobbin supporting case from circular movement with said loop taker, said bobbin supporting case being formed with a bobbin accommodating cavity, and a linear work feeding mechanism effective to advance work fabrics on said work support from said needle aperture in a direction radially outwardly from said loop taker axis, means for sewing chain stitches using thread carried by said needle comprising a thread loop engaging finger carried beneath said work support and having a free extremity extending in a direction away from said work support substantially parallel to said path of endwise needle reciprocation and arranged at that side of said path of needle reciprocation which is opposite the direction of advancement of work fabrics by said work feeding mechanism, means shiftably supporting said thread loop engaging finger relatively to said frame for movement substantially along the line of Work feed of said work feeding mechanism, said thread loop engaging finger being formed with an opening extending substantially parallel to the line of Work feed of said work feeding mechanism, a plate insertable in said bobbin accommodating cavity of said bobbin supporting case, means for constraining said plate in a predetermined angular position on said bobbin supporting case, said plate being formed with a projection positioned by said constraining means so as to be embraced by said opening in said thread loop engaging finger, means operated by said work feeding mechanism for shifting said thread loop engaging finger into embracing relationship with said projection during each release of said thread loop by said loop taker, a thread stripping element disposed between said thread loop engaging finger and the path of endwise reciproca- 16 tion of said needle and means for reciprocating said stripping element in timed relation with said endwise reciprocation of said needle and toward the free end of said thread loop engaging finger as said needle penetrates said needle aperture.

7. In a sewing machine having lock stitch forming instrumentalities including, a frame having a work support formed with a needle aperture, a thread-carrying eyepointed needle supported above said work support for endwise reciprocation through said needle aperture, a circularly moving loop taker disposed below said work support on an axis substantially parallel to the path of endwise reciprocation of said needle, and a bobbin supporting case journaled in said loop taker, stop means sustainedon said frame for constraining said bobbin supporting case from circular movement with said loop taker, said bobbin supporting case being formed with a bobbin accommodating cavity, and a linear work feeding mechanism effective to advance work fabrics on said work support from said needle aperture in a direction radially outwardly from said loop taker axis, a bobbin thread pull-01f device including an arm disposed on that side of the path of endwise needle reciprocation which is opposite the direction of advancement of work fabric by said work feeding mechanism and means for imparting reciprocating movement of substantially constant amplitude to said bobbin thread pull-off arm, means for sewing chain stitches using thread carried by said needle comprising, a thread loop engaging finger carried beneathsaidwork support and having a freejextremity extending in a direction away from said work support substantially parallel to said path, of endwise needle reciprocation and arranged at that side of the path of reciprocation of said bobbin thread pull-01f arm which is opposite the direction of advancement of work fabrics by said work feeding mechanism, means shiftably supporting said thread loop engaging finger relatively to said frame for movement substantially along the line of work feed of said work feeding mechanism, said thread loop engaging finger being formed with an opening extending substantially parallel to the line of work feed of said work feeding mechanism, a thread directing mem ber carried by said bobbin supporting case and formed with a projection adapted to be embraced by said opening in said thread loop engaging finger, means operated by said work feeding mechanism for shifting said thread loop engaging finger into embracing relationship with said projection during each release of said thread loop by said loop taker, and said arm of said thread pull-off device providing a stripping element for urging thread loops from said thread loop engaging finger as said needle penetrates said needle aperture.

8. In a sewing machine for sewing lock stitches in a work fabric and including an endwise reciprocatory work penetrating thread carrying needle, a loop taker, including a bobbin supporting case, means for imparting cooperating movements to said needle and loop taker for seizure by said loop taker during Work penetration of said needle and manipulation by saidloop taker of said seized needle thread loops about i said bobbin accommodating case, and a needle thread take-up mechanism including a thread engaging element movable relatively to thread guides carried on said sewing machine to slacken said needle thread during said seizure and manipulation by said loop taker to provide sufiicient thread for manipulation by said loop taker and to tighten said needle thread after manipulation by said loop taker to set said thread loop manipulated by said loop taker into the work fabric prior to the succeeding work penetration of said needle, the combination of chain stitch conversion fittings comprising thread loop engaging means positioned adjacent to the path of reciprocation of said needle for detaining each needle thread loop manipulated by said loop taker from being set into the work fabric until after said detained loop is entered by said needle on the succeeding Work penetration thereof, thread loop stripping of needle thread loops formed means operated in timed relation with said means for im parting cooperating movements to said needle and loop taker for removing said needle thread loops from said thread loop engaging means after entry thereof of said needle, and an auxiliary thread guide means provided on said sewing machine for cooperation with said needle thread take-up mechanism so as to reduce the quantity of the needle thread slackened by said take-up mechanism by an amount at least equal to the length of said thread loop removed by said thread loop stripping means from said thread loop engaging means whereby the thread necessary for said manipulation by said loop taker must be obtained by setting said thread loop removed from said thread loop engaging means into the work fabric.

9. In a sewing machine for sewing lock stitches in a Work fabric and including an endwise reciprocatory work penetrating thread carrying needle, a loop taker, including a bobbin supporting case, means for imparting cooperating movements to said needle and loop taker for seizure by said loop taker of needle thread loops formed during work penetration of said needle and manipulation by said loop taker of said seized needle thread loops about said bobbin accommodating case, and a needle thread take-up mechanism including a thread engaging element movable relatively to thread guides carried on said sewing machine to slacken said needle thread during said seizure and manipulation by said loop taker to provide sufiicient thread for manipulation by said loop taker and to tighten said needle thread after manipulation by said loop taker to set said thread loop manipulated by said loop taker into the work fabric prior to the succeeding work penetration of said needle, the combination of chain stitch conversion fittings comprising thread loop engaging means positioned adjacent to the path of reciprocation of said needle for dework penetration thereof, thread loop stripping means op- 5 erated in timed relation With said means for imparting cooperating movements to said needle and loop taker for removing said needle thread loops from said thread loop engaging means after entry thereof of said needle, and

means carried on said bobbin supporting case Within said 1 loop taker and formed with a thread camming surface for forming a bight in said thread loop manipulated by said loop taker sufficiently large as to reduce the availability to the loop taker of the quantity of the needle thread slackened by said take-up mechanism by an amount at 15 least equal to the length of said thread loop removed by said thread loop stripping means from said thread loop engaging means whereby the thread necessary for said manipulation by said loop taker must be obtained by setting said thread loop removed from said thread loop 20 engaging means into the work fabric.

References Cited by the Examiner UNITED STATES PATENTS 5 727,053 5/03 Anthony 112168 1,111,167 9/14 Molyneux 112246 X 2,999,472 9/61 Yamano 112-168 FOREIGN PATENTS 30 58,545 9/91 Germany.

809,217 2/59 Great Britain.

JORDAN FRANKLIN, Primary Examiner.

Claims (1)

1. IN A SEWING MACHINE HAVING LOCK STITCH FORMING INSTRUMENTALITIES INCLUDING A FRAME HAVING A WORK SUPPORT FORMED WITH A NEEDLE APERTURE, A THREAD CARRYING EYEPOINTED NEEDLE SUPPORTED ABOVE THE WORK SUPPORT FOR ENDWISE RECIPROCATION THROUGH SAID NEEDLE APERTURE, A CIRCULARLY MOVING LOOP TAKER DISPOSED BELOW SAID WORK SUPPORT, MEANS FOR DRIVING SAID NEEDLE AND LOOP TAKER IN TIMED RELATION FOR THE SEIZURE OF A LOOP OF THREAD FROM THE EYE OF THE NEEDLE BY SAID LOOP TAKER DURING EACH STROKE OF THE NEEDLE DOWNWARDLY THROUGH SAID NEEDLE APERTURE AND THE RELEASE OF SAID SEIZED LOOP BY THE LOOP TAKER DURING EACH SUCCEEDING UPWARD STROKE OF THE NEEDLE, A NEEDLE THREAD TAKE-UP MECHANISM EFFECTIVE ALTERNATELY TO DRAW TIGHT AND TO SLACKEN SAID NEEDLE THREAD, A BOBBIN SUPPORTING CASE JOURNALED IN SAID LOOP TAKER, STOP MEANS SUSTAINED ON SAID FRAME FOR CONSTRAINING SAID BOBBIN SUPPORTING CASE FROM CIRCULAR MOVEMENT WITH SAID LOOP TAKER AND, LINEAR WORK FEEDING MECHANISM EFFECTIVE TO ADVANCE WORK FABRIC ON SAID WORK SUPPORT IN ONE DIRECTION FROM SAID NEEDLE APERTURE BETWEEN EACH NEEDLE PENETRATION THEREOF, MEANS FOR SEWING CHAIN STITCHES USING THREAD CARRIED BY SAID NEEDLE COMPRISING A THREAD LOOP ENGAGING FINGER CARRIED BENEATH SAID WORK SUPPORT AND HAVING A FREE EXTREMITY EXTENDING IN A DIRECTION AWAY FROM SAID WORK SUPPORT SUBSTANTIALLY PARALLEL TO SAID PATH OF ENDWISE NEEDLE RECIPROCATION AND ARRANGED AT THAT SIDE OF SAID PATH OF NEEDLE RECIPROCATION WHICH IS OPPOSITE THE DIRECTION OF ADVANCEMENT OF WORK FABRIC BY SAID WORK FEEDING MECHANISM, MEANS SHIFTABLY SUPPORTING SAID THREAD LOOP ENGAGING FINGER RELATIVELY TO SAID FRAME FOR MOVEMENT SUBSTANTIALLY ALONG THE LINE OF WORK FEED OF SAID WORK FEEDING MECHANISM, SAID THREAD LOOP ENGAGING FINGER BEING FORMED WITH AN OPENING EXTENDING SUBSTANTIALLY PARALLEL TO THE LINE

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