US2434608A - Sewing machine - Google Patents

Description

1948- N. v. CHRISTENSEN 2,434,603

SEWING MACHINE Filed Dec. 8,' 1943. V 6 Sheets-Sheet l INVENTOR.

NORMA/V ucwk/s re/vss/v ATZOMEY Jan. 33, 1948. N. v. CHRISTENSEN SEWING MACHINE Filed Dec. 8, 1943 6 Sheets-Sheet 2 TENJE/Y b mi Jan. 13, 1948. N. v. CHRISTENSEN 2,434,603v

SEWING MACHINE Filed Dec. a, 1943 6 Sheets-Sheet 3 Hillilllillli v I mmvrox NORMAN 1 CHRISTENSEN I BY d T TOZFAE'Y 4 N. v. CHRISTENSEN 3 SEWING MACHINE Filed Dec. a, 1943 6 Sheets-Sheet s INVENTOR. I NORMA/y KC'HR/STE/VSE/Y N. V. CHRISTENSEN Jan. 13, 1948.

SEWING MACHINE -Fi1ed Dec. 8, 1943 6 Sheets-Sheet 6 g WW IN VEN TOR.

NORMA/V 1 CH1? ISTE/YSE/Y Patented Jan. 13, 1948 NlTED STATES PATENT OFFICE SEWING MACHINE Norman V. Christensen, Chicago, 111., assignor to Union Special Machine Company, Chicago,-Ill., a corporation of Illinois Application December 8, 1943, Serial No. 513,336

17 Claims. I

This invention relates to an improved sewing machine construction and. more particularly to the devices for handling and controlling the thread supplied to the needle of such a machine.

In the operation of a sewing machine, and particularly a two-thread, chain-stitch machine, the needle-thread requirement varies substantially with the thickness of the work being stitched. Thus, as a fold or overlap in the work is encountered in the course of forming a seam, additional thread is required for each stitch formed in the portion of the work which is of extra thickness. Each such stitch requires an added length of needle thread equal to twice the extra thickness of the work. Ordinarily the amount of needle thread to be used in the formation of a stitch during a given cycle of the machine must be made available toward the end of the preceding cycle of operation. The movement of the needle and other devices engaging the thread are such, during one operation, as to cause the normally re quired amount of thread to be drawn from the source of supply for the next stitch forming operation. Or, if the cycle is considered as beginning at the point at which the needle is just leaving the work, the thread required for a particular stitch may be said to be made available at the beginning of the same stitch forming operation. However, unless special provision is made, there will be no allowance for a sudden increase in the amount of thread required in the formation of such a stitch. A sudden increase in the thread requirement Will occur whenever a seam or fold in the Work is initially brought, by the operation of the work feeding mechanism, into the plane of action of the needles. This normally occurs, except in needle feed machines, while the needle is above the work and usually on the upstroke of the needle. If a machine happens to be working on four plys of material and a seam or fold is thus suddenly brought into the plane of the needles, thereby increasing the thickness of the work to eight plys, a substantial increase in the needle thread required on the next downstroke of the needles will be encoun tered. This is especially true in connection with operations upon heavy fabrics, such as denim and the like.

Various schemes have been suggested heretofore for insuring the provision of extra needle thread as the thickness of the work increases and some of these have involved control of the thread by work engaging means responsive to variations in the thickness of the work. But

none of these prior schemes have been fully satisfactory. They have made the extra thread availableeither toolate or too soon to insure a proper continuous seaming operation. When the extra thread is made available too late, the thread is subjected to excessive strain during the first stitch forming cycle in which the thread requirement is increased, with the result that the thread frequently breaks'at such times. On the other hand, if the extra thread is provided too early, excessive slack is produced, at least for a stitch or two, and this may either become entangled with, and interfere with the proper operation of, the stitch forming devices or it may prevent the iormationof tight stitches. Furthermore, if the extra thread is provided a number of stitches in advance of its actual requirement, it may be consumed before it is really needed and the same difliculty, in the way of thread breakage, may be encountered as if no extra thread were provided atalL- A It has been a primary object of the present invention to provide thread controlling devices which will serve to supply extra thread to the needle or needles, of a machine of the character hereinabove specified, in the particular stitch forming cycle in which it is needed. In accomplishing this purpose, the operations of the various instrumentalities of the machine are so 00- related that the work is fed as the needles are carried out of and moved away from the work, and simultaneously the take-up means for the needle thread will first operate to set the stitch, which has just been formed, and then operate to draw from thesource of supply the amount of thread required for thenext stitch forming operation. The arrangement is such, furtherm0re,-that if the feeding of the work, at this point in the operation, has served to bring an extra thickness of work into the plane of operation of the needles-an additional amount of thread will be drawn from the source of supply to take care of such extra thickness of the work. On the other hand, if the feeding of the work has served to carry a thinner portion of the work into the plane of the needles, the thread controlling devices will serve to correspondingly decrease the amount of threaddrawn from the source of supply during this cycle'of the machine.

A further objectof the invention has been to provide simple,="reliable and inexpensive mechanism'for achieving the foregoing purpose.

Toward the ends indicated above,an' important feature of theinventionis'theprovisionof a work engaging member. whichiis responsive to the thickness 7 of the 'work; substantially in the vertical plane containing the needle or needles and extending transversely to the line of feed. This work engaging member is so connected with a needle thread controller as to cause the latter to bring about an increase or decrease in the amount of thread available for the next stitch as the member responds to an increase or decrease in the thickness of the work,

In the preferred embodiment of the invention a tandem presser foot construction is employed and the forward presser foot member is mounted for both rocking and bodily movement. The pivot for the rocking movements is substantially in a vertical plane containing the axis of the needle bar and transverse to the line of feed. The arrangement is such, moreover, that the rocking movements of the forward presser foot member cause little or no change in the position of the pivot. Operation of the thread controller is made responsive to movements of the pivot which represent, in eiIect, bodily movements of the presser foot member. These movements occur only as a fold or other increased thickness of the work reaches the point of stitch formation. Preferably, the connections between the forward presser foot member and the thread controller are direct and are independent of the presser bar through which a yielding force'is transmitted to the presser foot member.

A special feature which may be embodied in the invention is the provision of spring means, or the like, for balancing or offsetting the weight of the connections to the thread controller which are supported by the pivot of the presser foot member. In this way, interference with the normal operation of the tandem presser foot structure is avoided.

Other objects, features and advantages of the invention will appear from a detailed description of an illustrative form of the same which will now be given in conjunction with the accompanying drawings, in which:

Fig. I is a side elevation of a machine embodying the invention, certain part-s being broken away for clearness of illustration.

Fig. II is a view, partly in plan and partly in horizontal section, of a portion of the machine, several cover plates being removed.

Fig. III is a vertical section through the needle head and adjacent portions of the machine, taken along the line IIIIII of Fig. II.

Fig. IV is a detail view in side elevation of needle head of the machine.

Fig. V is an enlarged view, chiefiy in plan but partly in section, of the presser foot construction embodied in the machine.

Fiv. VI is a detail view in elevation showing a portion of the presser bar and the tandem presser foot structure associated therewith.

Fig. VII is a detail view showing, largely in elevation but partly in vertical section, the presser foot structure and associated devices including the thread controlling means and other thread handling devices.

Fig. VIII is a view similar to Fig. VII but showing the parts in a difierent position, to which they are shifted as a fold or seam in the work is carried beneath the forward presser foot member.

Fig. IX is a detail view, in front elevation, showing a portion of a modified form of connection between the presser foot member and the thread controller, and

Fig. X is a view in side elevation of the same parts as are'shown in Fig. IX.

For purposes of illustration, the invention has the ' be applied to said Christensen and Le Vesconte been shown applied to a feed-ofi-the-arm sewing machine of the general type disclosed in the U. S. patent to Norman V. Christensen and Harold J. Le Vesconte, No. 1,741,095, granted December 24, 1929, the machine embodying certain modifications disclosed in the pending application of George Sauer, Ser. No. 499,789, filed August 24, 1943, now Patent No. 2,430,369, granted November 4, 1947. It will be understood, however, that the thread controlling devices forming an important part of the present invention may other types of sewing machine in which it is desirable to compensate for variations in the thickness of the work in the pulling-off of thread from the source of supply, during each stitch forming cycle, to make it available for the next stitch-forming operation, or a later period in the same cycle.

Referring now to the drawings, the illustrative machine comprises a frame having a main base or support 10 extending upwardly and laterally in a sweeping curve and terminating in a horizontally disposed body portion II at one end of which is formed a downward extension l2 carrying at its lower end a horizontally projecting work supporting arm l3. From the opposite end of .the portion H of the frame, there projects laterally a needle head portion I4 which extends over the free end of the arm I3. Power is supplied to the machin through a combined hand wheel and pulley 15 secured to the end of a shaft is journaled in suitable bearings carried by the portion ll of the frame. Pulley 15 may be connected by belt with any suitable source of power, such as an electric motor, not shown. The shaft 18 may be formed in a plurality of sections, suitably joined or coupled together, and may be provided in the region of the needle head with a crank portion 11 arranged to receive one end of a pitman =18 (Figs. II and III). This pitman is connected at its opposite end with a needle lever l9 pivoted at 20 in the frame of the machine. At its opposite end the needle lever is connected, by a link 2|, with a block 22 secured to a needle bar 23 whichcarries at its lower end one or more needles 24. Through the connections described, the needles will be reciprocated to carry their thread receiving eyes from a point above the work supporting surface 25 of the arm 13 to a point below said surface for cooperation with suitable complementary stitch forming means. This means may be in the form of one or more thread carrying'loop takers 24a operated by suitable connections from the shaft I6, such as disclosed in patent and said Sauer application above mentioned. Within the work supporting arm I3 there is also provided a work feeding dog 26 (Figs. VII and VIII) which may suitably be of the four-motion type and operated by appropriate connecti0ns from the shaft 16, as disclosed in said patent and application.

Cooperating with the work support and the feed .dog 26, and serving to hold the work in proper engagement with the latter, is a presser foot structure including apresser bar 21 which is yieldingly urged downwardly by a spring 28. The construction and mounting of the presser bar may suitably 'be of the type disclosed in the patent to Kucera, No. 2,103,470, granted December 28, 1937. At the lower end of the presser bar there is mounted a yoke 29 (Fig. VI) having pivotally mounted thereon. by means of screws 30, a rockable frame 3|. This frame is adapted to carry ,a pair of presser foot members 32 and 33 arranged in tandem. The rearward presser foot member 32 is pivotally mounted upon the rockable frame by a pair of screws 34 while the forward presser foot member 33 is pivotally mounted upon the forward end of the frame 3! by means of screws 35 (Figs. V and VI). It will be understood that the presser foot structure as a whole is urged downwardly toward the work support by the spring 28 which serves to carry both of the presser foot members into engagement with the work. However, to insure the proper action of the presser foot members under various conditions met with in the operation of the machine, a number of springs are provided in direct'association with said members. These include a light spring 36 secured to the frame 3| by a screw 31 and having a fiat, straight portion thereof in engagement with the upper surface of a block 38 integral with or otherwise secured to the member 33. This springthus serves to urge the member 33 into a predetermined position in relation to the frame 3 1. Another small spring 39 secured to the rearward portion of the frame 3i bears against the forward edge of the member 32 and urges this member in a clockwise direction (Fig. VI) about its pivot 34. Another spring 2!! is connected by a screw '3! with the rearward end of the member 32 and has its fr e end in engagement with a screw plug 42 carried by an intermediate relatively movable portion of the member 32 substantially over the pivot 34. Said intermediate portion may thus be permitted to rise and fall slightly in relation to the rest of the member 32, in opposition to spring so, or it may be locked in set position by a screw 42a. For further details as to the construction of the presser foot, reference may be had to the patent to Thompson No. 1,988,401, granted January 15, 1935. Still another spring 43 secured by a screw 43a to a shoulder of the yoke member 29 bears upon a forwardly extending arm of the frame BI and thus urges the latter in a clockwise direction (Fig. VI).

This brings us to the special connections provided from the forward presser foot member 33 to a thread controller for varying the amount of needle thread available for the stitch forming operation. These connections comprise a 6 link 44 pivotally attached to one of the screw pins 35, as best shown in Figs. I, V, VII and VIII. It should be observed in this connection that the pivot 35 for the forward presser foot member 33 is substantially in the vertical plane which contains the axis of the needle bar and extends transversely to the line of feed. The C form of the link 44 is for the purpose of providing easy access to the needles and allowing a stream of cooling air to be blown across the path of the same, as disclosed in the application of George Sauer Serial No. 442,585, filed on May 12, 1942, now Patent No. 2,418,429, granted April 1, 1947. At its opposite end the link is attached to the lower end of a vertically slidable rod or bar 45 mounted in suitable bearings 46 carried by the end cover plate of the needle head. At its upper end the rod or bar 45 carries a, forked member 4?, the forked, free end of which is adapted to straddle and slide along the presser bar 27 and thus prevent rotation of the rod 45. Intermediate the ends of the rod 45 there is secured thereto a block 48 having a laterally projecting portion s9 (Figs. I and II) to the outer end of which there is pivotally attached, by means of a screw 59, a link This link, which extends downwardly, has its lower end pivotally connected by a screw 52 with an arm 53 of a lever pivoted at 54 upon the needle head (see Fig. IV). Another arm 55 of this lever which extends inwardly toward the main frame portion of the machine carries atits inner end a thread controlling element 56. This element is preferably adjustably mounted at the end of the lever by means of a screw 51 cooperating with an elongated slot 58 in the element,

The thread for stitch forming purposes may be supplied through a tension device of the general type disclosed in the patent to Berger et a]. No. 1,758,349, granted May 13, 1930. The looper threads 5911 may be controlled and led to the loopers in the manner disclosed in said last mentioned patent and the means employed for this purpose will not be described herein. The needle threads 59 are passed from their source of supply through suitable openings in a pair of guide members 60 (Figs. II and VII) and the threads are then passed between the discs 6| of an appropriate tensioning device. They are then led to a suitable guide 52 and thence to and through a lower guide 63 from which the threads are passed through spaced openings in the thread controller 55. From this point the two needle threads, provided in the illustrative machine, are passed through alined openings in the two arms of a U-shaped take-up member 64 (Figs. II and IV). One of the arms of this member is passed through an arcuate slot 65 in the side wall of the needle head and is secured by screws or the like to the side of the needle lever l9. Thus, the take-up element is reciprocated through an arcuate path upon each stitch forming cycle of the machine and carries a portion of the needle thread through such path. At the lower end of the travel of the element 64 the threads extending between the two arms of the element are carried against a fixed guide 66 which serves to form a small loop in the thread to provide a desired take-up action as the needle bar approaches the lower end of its travel. The guide 66 is formed as a laterally projecting finger on a plate 61 which is adjustably secured by a screw 61a to the side wall of the needle head. A screw 68 co operating with an arcuate slot in the plate 6! permits the latter to be rocked, for purposes of adjustment, about the attaching screw 61a. This allows a desired variation in the length of the loop formed as the threads carried by the element 64 are brought against the guide 66. From the take-up element 64 the threads are passed downwardly, as shown in Figs. VII and VIII, to the eyes of the needles 2t and then through the fabric, around the loopers 24a, back to the line of stitching in the fabric.

As previously indicated, the timing of the various take-up actions upon the threads is such that the preceding stitch is set as the needles are moving upwardly above the work and are approaching the upper limit of their travel. When the stitch is finally set, the take-up element 64 may be approximately in the full-line position indicated in Figs. VII and VIII. At this time, as will be seen, the thread below the work support is passed around a relatively broad, smooth surface on the looper 25a, thus reducing to a minimum the strain on the thread and the tendency to sever the latter. As the take-up element 64 continues its upward movement, from the full-line to the dotted-line position indicated in Figs. VII and VIII, the thread, being firmly held at the fabric, will be drawn from the source of supply through the tension discs 5i, thus providing the extra thread needed during this continued upward movement of the take-up. The thread so drawn from the source of supply should be sufiicient for theformation of the next stitch. However, unless special provisions are made, as in accordance with the present invention, it will simply correspend with the thread consumed in forming the preceding stitch. This may be either more or less than is required for-thenext stitch, or just sufficient, depending upon what, if any, variation has taken place in the thickness of the work.

In connection with the foregoing. it should be observed thatin the formation of a stitch, when the needles 24 are approaching the lower end of their downward travel the thread spanning the arms of the thread take-up element 64, cooperating with the guide 66, will produce a suflicient take-up action to remove the slack from the loop which will at this time have been released by the loopers 24a. This take-up action will have partially set these loops against the under side of the work, thus eliminating any danger of entanglement of these loops with the loopers as they are oscillated again to enter the next needle thread loops.

Referring now particularly to Figs. VII and VIII, it will be noted that in Fig. VII the presser foot and the needles are cooperating with only a relatively thin portion of the work. At this time the thread controller 56 is in a relatively high position, substantially in a horizontal line with respect to the guide openings in the element 63. By proper adjustment of the parts, such a condition may be obtained that in moving from the full to the dotted-line positions, the take-up element 64 will draw just enough thread from the supply to provide what is required for the next stitch forming operation. Now, as a seam S in the work approaches the forward presser foot, by virtue -of the feeding action upon the work, the forward presser foot member will be tilted about its pivots 35. This initial tilting of the member, however, will not cause any substantial bodily movement of the pivots. Such bodily upward movement of the pivots and presser foot member will occur only as the seam S is carried substantially beneath the pivots 35, as shown in Fig. VIII. At this time the seam S will be positioned at least in part in the path of the needles and will require an additional amount of thread in the formationof the next stitch. It should be observed in this connection that the advance of the work into the position of Fig. VIII will have occurred during the upward movement of the needles and while the latter are above the work. It is'at this time that the improved thread controller becomes effective to insure the drawing off from the source of supply of suflicient thread to provide for the proper formation of the next stitch. As clearly indicated in Fig. VIII, this is accomplished by the lowering of the controller 56 in response to the lifting of the rod 45 just as the seam S is brought up to the stitching point. The preceding stitch will have been set at a slightly earlier point in the upward movement of the take-up element 64, because of the lengthening of the path of the thread between the guide 63 and the element-64 due to the lowering of the controller 56. This lowering of controller 55 will have taken up a part of theslack in the thread. 'According'ly,-.in continuing its upward movement, after proper setting of the preceding stitch, the take-up .54 will draw a greateramount of thread than previously from the source of supply through the tension discs'fi ,thereby providing'for the increased length of the path of the thread :from the guide :63 to the dotted-line position :of the 8 take-up 64. The additional threadso withdraw-n from-the source of supply is then rendered available for the next stitch-forming operation. In this connection it should be noted that the position of the controller 56 is such'that it will'not materially alter the take-up action, hereinabove described, which occurs at the lower end of the down strokeof the needles.

Referring now to Fig. III, there is shown a conventional form of manual or foot-operated presser foot lifting mechanism. This may include a block "lllsecured to the presser bar, such block having a rearwardly extending arm H adapted to'be engaged by an arm 12 secured'to a rock shaft 13. The latter has anupwardly extending arm 14 connected by -a link I5 with a rock lever'lfi pivoted at'l'l upon theframe. Lever 16 may be operated manually or by a foot 'treadle connected with the rearwardly extending arm of the lever by a chain 18. Lifting 'of the presser foot structure in this manner will, of course, have its effect upon the thread controller 56, i. e., will depress the latter in the same manner as if the forward 'presser foot member 33 were lifted by the fabric. However, the manual lifting of the presser bar usually occurs while the machine is at rest and the controller 56 will be returned to its normal position before the operation of the machine is resumed. Whatever additional thread may be drawn from the supply because of the momentary downward movement of the controller will be taken up in the first subsequent stitch forming operation of the machine. Moreover, it should be observed that in lifting the presser bar the action of the various springs, particularly spring 43, is such that the frame 3| will be tilted in a clockwise direction so that the pivot 35 of the forward presser foot member will be raised only slightly.

Turning now to Figs. IX and X, there is shown a modified construction differing from that disclosed in Figs. I to VIII, inclusive, only in the connection between the rod or'bar 45 and the lever arm 53 of the thread controlling mechanism. These parts are designated 45a and 53a, respectively in the modified construction. A block 48a corresponding with'block48 of the first embodiment is secured to the rod or bar45a at a somewhat higher point than in the first embodiment'and a link 5m of-somewhat greater length than link 5| is provided to connect the block 48a with the lever arm 53a. This construction provides room beneath the block 48a for a collar 19, secured to the rod 45a, against which bears the upper end of a spring which surroundsthe rod 45a. At its lower end the spring bears against the upper end of the lower bearing46a in which the rod 45a is slidably mounted. This arrangement is such that the spring 80 counter-balances the weight of the rod 45a and the connected parts and thus avoids the application of an-extra force to the pivot of the forward presser foot member 33. The normal operation of the presser'foot'is thus-maintained.

While an illustrative formof the invention has been disclosed in considerable detail and apossible modification has been explained, it will be understood that numerous other changes'may be made in'the form and arrangement of the various parts, within the scope of the appended claims, without departingfrom thegeneral principles-of the invention.

I claim:

'1. In a sewing machine, stitch-fomnngdevices including a reciprocable needle, :work :feedmg means, presser means for yielding'ly urging work against said work feeding means, means for controlling the supply of needle thread to said needle comprising a thread engaging and shifting element having an invariable extent of movement and an adjustable controlling member operable in conjunction therewith, and means associated with said presser means responsive always to the thickness of the work at a point less than a stitch length from the point at which the needle penetrates the work and cooperating with said controlling member'to adjust the same and thereby increase the length of the available needle thread upon an increase in the thickness of the Work in the course of the same stitch forming cycle in which it is required.

2. In a sewing machine, stitch forming devices including a reciprocable needle, work feeding means, presser means for yieldingly urging work against said work feeding means, means for controlling the supply of needle thread from a source of supply to said needle, said last recited means including a thread tensioning device, a shiftable guide element for varying the path of the thread between said device and the needle and a thread engaging and shifting element having an invariable movement, and means associated with said presser means responsive to the thickness of the work at less than a stitch lengthfrom the stitching point for shifting said guide element to increase the available thread between said tensioning device and needle upon an increase in the thickness of the work in the same stitch forming cycle in which the demand for additional thread occurs.

3. In a. sewing machine having a Work support, a presser foot movable toward and away from said support and adapted to urge work against the same, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the work upon stitch forming cycles, means responsive to variations in the thickness of the work just as said variations reach said predetermined point, said responsive means and presser foot being arranged to move relative to each other at times and to move concurrently as the variation in thickness of the wor reaches said point, and connections between said thickness responsive means and said adjustable means.

4. In a sewing machine having a work support, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the work upon stitch formins cycles, and means responsive to variations in the thickness of the work on said support just as said variations approach said point connected with said controlling means for positioning the same, said means including a bar disposed substantially in a vertical plane transverse to the line of stitching at said predetermined point and a rockable work engaging element connected with said bar for movement therewith but capable of rocking movement independently of said bar.

5. In a sewing machine having a work support, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the Work upon stitch forming cycles, and means responsive to variacomprising a plurality tions in the" thickness of the work on said support connected with said controlling means for positioning the same, said means including a pivoted work engaging element having its pivot substantially in a plane transverse to the line of stitching which contains the needle, and connections from said pivot to said controlling means.

6. In a sewing machine having a work support, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the work upon stitch forming cycles, a spring urged presser bar, a plurality of pivoted work engaging elements carried by said bar and arranged in tandem, and connections from the foremost of. said elements to said adjustable means for positioning thesame.

7. In a sewing machine having a work support, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the work upon stitch forming cycles, a spring urged presser bar, a plurality of pivoted work engaging elements carried by said bar and arranged in tandem, said elements being shiftable vertically independently of each other, and connections from the foremost of said elements to said adjustable means for p0- sitioning the same in response to vertical movement of said foremost element.

8. In a sewing machine having a work receiving surface, stitch forming devices including a reciprocable needle arranged to cooperate with work held against said surface, presser means comprising a plurality of elements yieldingly urged against said work, said elements being shiftable bodily by the work in response to Variations in thickness thereof independently of each other, and means shiftable in response to bodily movements of only one of said elements for controlling the supply of thread to said needle.

9. In a sewing machine surface, stitch forming devices including a reciprocable needle arranged to cooperate with work held against said surface, presser means comprising a plurality of elements yieldingly urged against said work, said elements being shiftable bodily by the work in response to variations in thickness thereof independently of each other, means for controlling the amount of thread available for stitch formation in each stitch forming cycle of the machine, and connections responsive to bodily movements of only One of said elements for operating said controlling means.

10. In a sewing machine having a work receiving surface, stitch forming devices including a reciprocable needle arranged to cooperate with work held against said surface, presser means comprising a spring urged bar, a frame pivotally mounted on said bar, and a plurality of Work engaging elements pivotally mounted on said frame and arranged in tandem, and means responsive to bodily movements of the foremost of said elements upon rocking of the frame for controlling the supply of thread to said needle.

11. In a sewing mechine having a work receiving surface, stitch forming devices including a reciprocable needle arranged to cooperate with work held against said surface, presser means of elements yieldingly urged against said work, a frame carrying said elements, said frame being mounted for both having a work receiving 11 rocking movement and bodily movement to carry said elements bodily and independently toward and away from said work receiving surface, and means responsive to bodily movement of only one of said elements for controlling the supply of thread to said needle. h

12. In a sewing machine having a work receiving surface, stitch forming devices including a reciprocable needle arranged to cooperate with work held against said surface, presser means comprising a spring urged bar, a frame pivotally mounted on saidbar, and a plurality of work engaging elements pivotally mounted on said frame and arranged in tandem, and means responsive to movements of the pivotal axis of the foremost of said elements in relation to said work receiving surface for controlling the supply of thread to said needle.

13. In a sewing machine stitch forming devices including a reciprocable needle, work feeding means, a presser foot and associated pressure means for yieldingly urging work against said work feeding means, means for controlling the supply of needle thread to' said needle, and means connected with said presser foot and independent of said pressure m'eans cooperating with said controlling means to increase the length of the available needle thread in the course of the same stitch forming cycle in which it is required.

14. In a sewing machine stitch forming devices including a reciproc'able needle, work feeding means, a presser foot and associated pressure means for yieldingly urging work against said work feeding means, means for controlling the supply of needle thread to said needle, and means connected with said presser foot and independent of said pressure means cooperating with said controlling means and responsive to variations in the thickness of the work within a stitch length of the stitching point for varying the length of needle thread available for a "stitch forming operation in the course of the same stitch forming cycle in which a variation in the requirement of needle thread occurs.

15. In a sewing machine stitch forming devices including a reciprocable needle; work feeding means, a presser foot and associated pressure means for yieldingly urging work against said work feeding means, means for controlling the supply ofneedle thread from a source of supply to said needle, said last recited means including a thread tensioning device arida shiftable guide element for varying the path of the thread be tween said device and the needlaarid means asso ciated with said presser foot and independent of 6 said pressure means forshifting said guide element to increase the available thread between said tensioning device and needle in the same stitch forming cycle in which the demand for additional thread occurs.

16. In a sewing machine stitch forming devices including a reciprocable needle, work feeding means, a presser foot arranged to yieldingly urge work against said work feeding means, means for controlling the supply of needle thread from a source of supply to said needle, said controlling means including a thread tensioning device, a take-up element coordinated with the movements of said needle and a shiftable guide element for varying the path of the thread from said tensioning device to said take-up element, said take-up element being arranged to set a stitch upon the movement of the needle away from the work and then draw thread through said tensioning device in preparation for the next stitch forming operation, and connections from said presser foot to said guide element for shifting the latter in response to variations in the thickness of the work and thereby varying in direct proportion the amount of thread so drawn through said tensioning device.

17. In a sewing machine having a work support, stitch forming devices including a reciprocable needle adapted to pass through work at a predetermined point on said support, adjustable means for controlling the amount of thread available to said needle as it enters the work upon stitch forming cycles, a spring urged presser bar, a plurality of pivoted work engaging elements carried by said bar and arranged in tandem, said elements being shiftable vertically independently of each other, and connections from the foremost of said elements to said adjustable means for positioning the same in response to vertical movement of said foremost element, said connections including a vertically slidable bar and spring means for counter-balancing the weight of said bar.

NORMAN V. CHRISTENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

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