US3083661A - Thread pull-off for sewing machines - Google Patents

Description

Aril 2, 1963 w. E. PATRICK 3,083,661

THREAD PULL-OFF FOR SEWING MACHINES Filed Oct. 15, 1959 4 Sheets-Sheet 1 IN VEN TOR. William E. Patrick WITNESS Fig Aril 2, 1963 w. E. PATRICK 3,083,661

THREAD PULL-OFF FOR SEWING MACHINES Filed Oct. 13, 1959 4 Sheets-Sheet 2 F i 3 INVENTOR.

9 William E. Patrick WITNESS m mym April 2, 1963 w. E. PATRICK THREAD PULL-OFF FOR SEWINGMACHINES 4 Sheets-Sheet 3 Filed Oct. 15, 1959 Fig.4

Aril 2, 1963 w. E. PATRICK ,0

THREAD PULL-OFF FOR SEWING MACHINES v Filed Oct. 15, 1959 4 Sheets-Sheet 4 INVENTOR.

Fig 5 William E. Pafrick WITNESS BY 9% W44 yaw TORNEY 3,083,661 Patented Apr. 2, 1963 3,683,661 THREAD PULL-OFF FQR SEWING MAQHINES William E. Patrick, Colonia, Ni, assignor to The Singer Manufacturing Company, Elizabeth, N..l., a corporation of New Jersey Filed Oct. 13, 1959, Ser. No. 846,130 3 Claims. (1. 112-242) The present invention relates to sewing machines and, more particularly, to a thread pull-off for sewing machines.

In a sewing machine, the needle thread is usually run from a supply through a tension device and take-up mechanism to the needle and then to the work. At stitch setting, the take-up mechanism tensions the thread by pulling on it between the end that is anchored in the work and the tension device, which is adjustable and which at a particular setting offers a certain specific resistance to drawing thread from the supply. The tension device determines the amount of tension that the take-up mechanism can apply to the thread in that any tension applied to the thread greater than the resistance oifered by the tension device at the particular setting will pull thread through the tension device from the supply. By limiting the tension that can be applied to the thread, the tension device determines the stitch setting characteristics of the machine. The total tension on the thread, however, is not solely a function of the tension device since the thread guides and other elements of the thread handling system also offer a resistance to the passage of the thread and, in addition, there is a certain pull required to draw the thread from the supply. The resistance to the passage of the thread otiered by most of the various elements in the thread system is substantially constant 'from stitch to stitch. This is not always true, however, of the etfort required to pull thread off the supply. For example, in a family type sewing machine, the thread supply usually consists of a thread spool mounted on a spool pin on the top of the bracket arm of the machine and when thread is pulled from the supply, the entire spool is rotated. Pulling thread from the supply occurs in a very small portion of the sewing cycle and is very quick so that, in eflfect, the thread is pulled in jerks.

Assuming that on one particular stitch the thread is taut between the tension device and the spool, all the thread pulled into the thread system at the end of that stitch must be pulled ofi the spool. As the spool is jerked to supply the thread, because of inertia of the spool, it will tend to continue rotating after pulling has ceased and will thus spill a certain amount of thread. Consequently, on the subsequent stitch, there is slack thread between the tension device and the thread spool so that no thread need be drawn off the spool. When the slack thread is consumed, thread must again be drawn off the spool. The effort required to jerk the thread off the spool has a considerable effect upon the total tension placed on the thread so that there is a substantial varia tion between the total tension on the thread on one stitch when thread must be drawn from the spool and the subsequent stitch when there is slack thread available. The result, of course, is erratic stitch setting.

In zigzag sewing machines, for example in sewing a satin stitch, a considerable amount of thread is required for each stitch and, in addition, a very low tension setting is required. In such a situation, the problem is aggravated since spilling of thread from the spool is more pronounced and the efiects of the variations in the total tension are greater and are more readily apparent because the bobbin thread is laid in a very erratic and very noticeable pattern.

vide a thread pull-01f means for a sewing machine, which means will provide a slack thread on the supply side of the tension device for every stitch, thereby efiectively isolating the thread supply from the thread tension system and providing a more nearly uniform thread tension. More particularly, it is an object of this invention to provide a thread pull-ofi means that is simple and economical, and at the same time, effective and reliable. The above objects have been attained in accordance with this invention by the provision of a thread pull-oft finger mounted on the needle bar driving crank and operable between a pair of spaced thread guides to pull a predetermined quantity of thread from the supply, the device being disposed between the thread supply and the tension device of the sewing machine and thereby providing slack thread on the supply side of the tension so that the stitch will be set against the tension alone and will not be affected by the varying force required to pull the thread from the supply. The arrangement of the pulloff finger on the needle bar driving crank provides for the use of a simple and economical element having an orbital movement which, in use for example with a link take up, is automatically optimumly timed with respect to stitch setting, will uniformly engage and release the thread upon each stitch, can be substantially concealed within the frame of the machine, and comprises a smooth and readily balanced action.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary elevational view of the head end of a sewing machine embodying the present invention,

FIG. 2 is a fragmentary detail view in elevation of that portion of FIG. 1 showing the thread pull-off, but with the parts in a diflerent operative position,

FIG. 3 is a fragmentary vertical sectional view longitudinally of the sewing machine of FIG. 1,

FIG. 4 is a fragmentary vertical sectional view taken substantially on theline 44 of FIG. 3,

FIG. 5 is a schematic view showing the paths of motion of the take-up lever and the pull-01f finger of the machine.

With reference to the drawings, there is illustrated a fragmentary portion of a zigzag sewing machine embodying the present invention, and particularly the sewing machine forming the subject matter of the United States patent of Johnson, No. 2,862,468. The machine includes a frame having a bed defining a work supporting surface 1 and abracket arm 2 overhanging the work supporting surface 1 and terminating in ahead 3.

Mounted in thehead 3 for vertical endwise reciprocation is aneedle bar 4 carrying aneedle 5 at its lower end. Theneedle 5 is adapted to penetrate work on the work supporting surface 1 and cooperate therebeneath with a loop taker (not shown) in the formation of lock stitches. For zigzag stitching, theneedle bar 4 is adapted to be oscillated to vibrate theneedle 5 laterally of the line of feed. For this purpose, theneedle bar 4 is supported in the lower portion of thehead 3 by aspherical bearing 6 which provides for endwise reciprocation of theneedle bar 4 and for universal pivotal movement as defined by thebearing 6. At its upper end, theneedle bar 4 is journaled in abore 7 in agate member 8 that is pivotally mounted on a presser bar bushing 9 and is Accordingly, it is an object of this invention to pro-connected by alink 10 to a zigzag mechanism for im- 3. parting vibrations to theneedle bar 4 for moving theneedle 5 laterally of the line of feed. The. details of the above mechanism form no part of the present invention ,and so are not herein disclosed. However, the disclosed mechanism is substantially the same as in the above mention Johnson patent, No. 2,862,468, to which reference may be had for a. more detailed disclosure thereof. a Endwise reciprocation is imparted to theneedle bar 4 by a counterbalanced crank 11 mounted on the head end of amain shaft 12 journaled longitudinally of the bracket arm 2 Acrank pin 13 is secured in the crank 11 by a set screw 14. One end of a connectinglink 15 is provided with ahub 16 having a bore for receiving thecrank pin 13, thehub 16 having a reducedportion 17 received Within a recess in the crank 11. The other end of thelink 15 has abore 19 slidably receiving apin 20 having integralthereofspaced cheeks 21 disposed upon opposite sides of theneedle bar 4. Thecheeks 21 support across pin 22 having avertical bore 23 for receiving theneedle bar 4 and aset screw 24 for locking the same relatively to the needle bar. r V V The take-up mechanism of the machine is of a conventional link type and comprises a take-up lever 25 pivotally mounted atone end on thecrank pin 13 and having a free opposite end extending through avertical slot 26 to the exterior of the head. A threadingeye 27 is formed in the free end of the take-up lever. Intermediate its ends, the take-up lever25 is pivotally connected by apin 28 to one end of ananchor link 29 that is pivotally connected at its other end by apivot screw 38 to aboss 31 formed in thehead 3.

The thread pull-off mechanism in accordance with this invention comprises a planar thread pull-offelement 32 formed of sheet metal and secured to the needle bar driving link-15. Theelement 32 is provided with ahole 33 receiving the reducedend 17 of the'hub 16 of thelink 15 and has anarm 34 secured to the face of the link -15 by ascrew 35. Theelement 32 has a pull-01f finger 36 having afree end 37 formed on the underside thereof with a thread-engaging surface 38. Upon rotation of the crank 11, thefree end 37 of thefinger 36 is projected through a vertically-arranged slot 39in the front wall of thehead 3.

Secured'on'the front face of thehead 3, as by n'vets 40, is aplate 41having'a slot 42 substantially coinciding with theslot 39 in thehead 3. Theplate 41 carries afirst thread guide 43 on one side of theslot 42 and asecond guide 44 on the other side of theslot 42. The guides43 and 44 are designed to direct the thread lead laterally across theslot 42 at a point intermediate the ends of theslot 42.

The machine includes athread tension device 45, for example, of the type illustrated in the United States patent application of Johnson, Serial No. 692,323, filed October 26, 1957, now Patent No. 2,955,775. Briefly, this thread tension device comprises a mountingstud 46 on which are arranged a' plurality oftension discs 47 that are biasedinto engagement with each other by a spring (not shown) disposed within a pair of telescoping spring covers 48, the compression of the spring'and thus the tension imposed upon a thread adapted to pass between thediscs 47 being regulated by an adjustingnut 49. The tension device also includes acheck spring 50 and aguard plate 51. Astop plate 52 is disposed between the tension device and the face of the-head 3 and is adjustably secured thereto by a screw 53. Thestop plate 52 iucludesan abutment 54- for the check spring '50 and a guar'd55 to facilitate threading. Behind thestop plate 52 there: is disposed aplate 56 carrying thread guides 57 and 58.

r The thread supply in the illustrated machine comprises athread spool 59 mounted on aspool pin 60 on the top of thebracket arm 2. From thespool 59, the thread T passes through aguide 61 to theguide 43 of theplate 41 andthen laterally across theslot 42 to theguide 44.

4 From theguide 44, the thread passes through the tension device 45' between a pair of thetension discs 47 and around thestud 46, through aguide 62 formed on theguard plate 51, thecheck spring 50, guide 58, theeye 27 of the take-uplever 25, the a-guide 57, guide 63 mounted beneath thehead 3, and a pair ofguides 64 and 65 on aneedle clamp 66, to the eye of theneedle 5.

With reference to FIG. 5, during operation of the machine, the crank 11 is rotated to move thecrank pin 13 in the direction of the arrow. As the needle bar approaches the top of its stroke, the take-uplever 25 is simultaneously approaching the top of its stroke. At this time, the take-up lever is pulling the sewing thread to set the stitch in the work and, in the final movements, drawing thread into the system through the tension device from the supply to replace the thread that was consumed in the stitch. The take-uplever 25 then begins to descend to make slack thread available for forming the next stitch and theneedle bar 4 begins to descend. It is at this time in the cycle that the thread pull-off acts to pull thread from the supply to make slack thread available on the supply side of the tension device. In FIG. 5, there is illustrated the path of movement at a point P onrthethread engaging surface 38 of the free end v37 of thefinger 36. Thefree end 37 of thefinger 36 is projected through theslot 39 at a point above the thread lead] between theguides 43' and 44 and then moves downwardly. The thread is isolated by thetension device 45 from the thread system of the machine so that as the thread lead between theguides 43 and 44 is expanded by thefinger 36, as illustrated in FIG. 2, a certain amount of thread is pulled from the spool 53. Thereafter, the free end of thefinger 36 is drawn back into thehead 3 and moves upwardly to begin another pull-off stroke, the upward movement of thefinger 36 leaving slack thread between theguides 43 and 44 which thread is available for when the take-up mechanism again pulls thread into the system through thetension device 45.

amount of slack thread left between theguides 43 and 44 which is the fixed amount initially provided by the pull-01f mechanism less the amount drawn into the thread system to replace the thread consumed in the stitch. When the pull-off mechanism is again operated,

. the thread limb between theguides 43 and 44 is expanded to the same extent as on the previous stitch, drawing from the spool 53 only the amount of thread'required to replace the thread drawn from there into thethread system.

ln'accordance with this invention, there has been provided a novel, simple and effective thread pull-01f mechanism that provides slack thread on. the supply side of the tension andthereby completely isolates the thread supply from the system so that it will be unable to effect the tensioning of the needle thread at stitch setting. At the same time, the thread pull-01f mechanism in accordance with this invention is substantially concealed in that it the work, and is protected so that it is not subject to damage. 7

Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. How-' ever, it is to be understood that the present disclosure relates to a preferred embodiment of my invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

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

1. In a sewing machine having a frame, a needle bar mounted in said frame for endwise reciprocation and having a work-penetrating stroke and a return stroke, a rotary shaft journaled in said frame, a crank on said shaft, a needle bar driving link pivotally connected at one end to said crank and at the other end to said needle bar for imparting endwise reciprocation to said needle bar upon rotation of said shaft, a thread take-up mechanism mounted in said frame, means operatively connecting said take-up mechanism and said shafit for actuating said take-up mechanism in synchronism with said needle bar to effect a maximum take-up action substantially simultaneously with the end of the return stroke of said needle bar, a tension device disposed between said take-up mechanism and the thread supply and a thread pull-oft mechanism disposed on the thread supply side of said tension device and comprising a pull-ofi element on said needle =bar driving link and having a thread engaging free end movable in a plane parallel to the plane of movement of said link and having a path of movement defined by the movement of said link, said frame having an opening in the plane of movement of the thread engaging end of said pull-01f element, said pull-off element being extended to project said thread engaging end through said opening during the work-penetrating stroke of said needle and to retract the same during the return stroke thereof, and thread guides defining a thread lead transversely of the path of movement of said thread engaging end of said pull-off element whereby said thread engaging end of said pull-oh element engages and expands said thread lead during the work-penetrating stroke of said needle and releases said thread lead during the return stroke of said needle.

2. In a sewing machine having a frame including a head, a, needle bar mounted in said head for endwise reciprocation, a rotary shaft journaled in said frame and extending into said head, a crank on said shaft within said head, a crank pin carried by said crank, a needle bar driving link pivotally connected at one end to said crank pin and at the other end to said needle bar for imparting endwise reciprocation to said needle bar upon rotation of said shaft, a take-up mechanism comprising a take-up lever pivotally mounted at one end on said crank pin and having a thread eye at the other end, an anchor link pivotally connected at one end to an intermediate point of said take-up lever and at the other end to said frame, a tension device disposed between said take-up mechanism and the thread supply, and a thread pull-0E mechanism disposed on the thread supply side of said tension device and comprising a pull-oft element on said needle bar driving link and having a thread engaging free end movable in a plane parallel to the plane of movement of said needle bar driving link and having a path of movement defined by the movement of said link, said head having an opening in the plane of movement of the thread engaging end of said pull-ofi element, said pull-01f element being extended to project said thread engaging end through said opening during the work-penetrating stroke of said needle and to retract the same on the return stroke thereof, and thread guides defining a thread lead transversely of the path of movement of said thread engaging end of said pull-ofi element whereby said thread engaging end of said pull-off element engages and expands said thread lead during the work-penetrating stroke of said needle and releases said thread lead during the return stroke of said needle.

3. In a sewing machine having a frame including a head, a needle bar mounted in said head for endwise reciprocation, a rotary shaft journaled in said frame and extending into said head, a crank on said shaft within said head, a crank pin carried by said crank, a needle bar driving link pivotally connected at one end to said crank pin and at the other end to said needle bar for imparting endwise reciprocation to said needle bar upon rotation of said shaft, a take-up mechanism comprising a take-up lever pivotally mounted at one end on said crank pin and having a thread eye at the other end, an anchor link pivotally connected at one end to an intermediate point of said take-up lever and at the other end to said frame, a tension device disposed between said take-up mechanism and the thread supply and a thread pull-off mechanism disposed on the thread supply side of said tension device and com-prising a pull-ofl'f element formed of sheet metal and having a thread engaging free end, means for pivotally mounting said element on said crank pin at one point and releasably securing said element to said needle bar driving link at another point for movement of said element in a plane parallel to the plane of movement of said needle bar driving link and having a path of movement defined by the movement of said needle bar driving link, said head having an opening in the plane of movement of the thread engaging end of said pull-oil element, said pull-ofi element being extended to project said thread engaging end through said opening during the work-penetrating stroke of said needle and to retract the same on the return stroke thereof, said thread guides defining a thread lead transversely of the path of movement of said thread engaging end of said pull-oif element whereby said thread engaging end of said pull-oft element engages and expands said thread lead during the work-penetrating stroke of said needle and releases said thread lead during the return stroke of said needle.

References Cited in the file of this patent UNITED STATES PATENTS 557,730 Trowbridge Apr. 7, 1896 1,133,608 Berger Mar. 30, 1915 1,166,834 Hemleb Jan. 4, 1916 1,549,081 "Hohmann Aug. 11, 1925 2,430,084 Smith Nov. 4, 1947 2,704,987 Court et al Mar. 29, 1955

Claims (1)

1. IN A SEWING MACHINE HAVING A FRAME, A NEEDLE BAR MOUNTED IN SAID FRAME FOR ENDWISE RECIPROCATION AND HAVING A WORK-PENETRATING STROKE AND A RETURN STROKE, A ROTARY SHAFT JOURNALED IN SAID FRAME, A CRANK ON SAID SHAFT. A NEEDLE BAR DRIVING LINK PIVOTALLY CONNECTED AT ONE END TO SAID CRANK AND AT THE OTHER END TO SAID NEEDLE BAR FOR IMPARTING ENDWISE RECIPROCATION TO SAID NEEDLE BAR UPON ROTATION OF SAID SHAFT, A THREAD TAKE-UP MECHANISM MOUNTED IN SAID FRAME, MEANS OPERATIVELY CONNECTING SAID TAKE-UP MECHANISM AND SAID SHAFT FOR ACTUATING SAID TAKE-UP MECHANISM IN SYNCHRONISM WITH SAID NEEDLE BAR TO EFFECT A MAXIMUM TAKE-UP ACTION SUBSTANTIALLY SIMULTANEOUSLY WITH THE END OF THE RETURN STROKE OF SAID NEEDLE BAR, A TENSION DEVICE DISPOSED BETWEEN SAID TAKE-UP MECHANISM AND THE THREAD SUPPLY AND A THREAD PULL-OFF MECHANISM DISPOSED ON THE THREAD SUPPLY SIDE OF SAID TENSION DEVICE AND COMPRISING A PULL-OFF ELEMENT ON SAID NEEDLE BAR DRIVING LINK AND HAVING A THREAD ENGAGING FREE END MOVABLE IN A PLANE PARALLEL TO THE PLANE OF MOVEMENT OF SAID LINK AND HAVING A PATH OF MOVEMENT DEFINED BY THE MOVEMENT OF SAID LINK, SAID FRAME HAVING AN OPENING IN THE PLANE OF MOVEMENT OF THE THREAD ENGAGING END OF SAID PULL-OFF ELEMENT, SAID PULL-OFF ELEMENT BEING EXTENDED TO PROJECT SAID THREAD ENGAGING END THROUGH SAID OPENING DURING THE WORK-PENETRATING STROKE OF SAID NEEDLE AND TO RETRACT THE SAME DURING THE RETURN STROKE THEREOF, AND THREAD GUIDES DEFINING A THREAD LEAD TRANSVERSELY OF THE PATH OF MOVEMENT OF SAID THREAD ENGAGING END OF SAID PULL-OFF ELEMENT WHEREBY SAID THREAD ENGAGING END OF SAID PULL-OFF ELEMENT ENGAGES AND EXPANDS SAID THREAD LEAD DURING THE WORK-PENETRATING STROKE OF SAID NEEDLE AND RELEASES SAID THREAD LEAD DURING THE RETURN STROKE OF SAID NEEDLE.

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