US2186762A - Thread controlling mechanism for sewing machines - Google Patents

Description

n4. oaWING MACHiNES.

Search Room Jan. 9, 1940.

THREAD M. MCCANN 2,186,762

CONTROLLING MECHANISM FOR SEWING MACHINES Filed Feb. 9, 1938 3 Sheets-Sheet 2 awucwto'a (1 tram;

Search Room Jan. 9, 1940. M. MCCANN 2,186,762

THREAD CONTROLLING MECHANISM FOR SEWING MACHINES Filed Feb. 9, 1938 3 SheetsSheet 3 Patented Jan. 9, 1940 UNITED STATES PATENT OFFICE THREAD CONTROLLING MECHANISM FOR SEWING MACHINES Application February 9, 1938, Serial No. 189,503

14 Claims.

This invention relates to sewing machines more particularly of the single-thread chain-stitch type adapted for the sewing of buttons to garments.

The single-thread chain-stitch button-sewing machine, as commonly constructed, is fitted with a needle-bar-vibrating cam cut so that the needle makes its last two or three complete reciprocations through the same thread-hole in the button without making any lateral movement and thus causes the usual final knot-tying stitches to be formed. When the needle descends successively through the same thread-hole in the button, a portion of the needle-thread is doubled back upon itself, and as the needle continues to descend this doubled portion of the thread is drawn into the work and held in such position by friction only until the advancing beak of the looper enters the subsequently formed thread-loop cast out by the needle as it begins to ascend, the doubled portion of the thread then being drawn down out of the work by the action of the take-up in setting the stitch. In practice, it has been found that when sewing buttons on a comparatively heavy material, such as that used in the making of overcoats and the like, skipping of stitches frequently occurs during the formation of the knot-tying stitches at the end of the button-sewing operation, resulting in a tack which may easily be raveled. It has been discovered that this skipping of the stitches is caused by the reeving of the thread through the eye of the needle as the latter descends causing only a very small portion of the needle-thread to be doubled back upon itself, and as a result this comparatively short length of doubled thread, instead of being held in the work, is drawn down out of the work before the needle reaches the bottom of its stroke. When this occurs, the thread-loop formed as the needle begins its upstroke is uncontrolled and, due to the tension on the needle-thread and the position of the previously formed stitches, is frequently drawn rearwardly of the needle, in which position it is practically impossible for the advancing beak of the looper to invariably seize the needle-thread loop. Obviously, when the needle-thread loop is not seized by the looper, no knot-tying stitch is formed and the resulting button-securing tack may, of course, be easily raveled. This fault is accentuated by the excessive straining of the needle-thread between the nipper and the preceding stitch in the work, since this straining of the thread tends also to prematurely reduce the needle-thread loop as the needle begins its upstroke and before the looper reaches its loop-seizing position. These conditions have existed in the past and are extremely troublesome in that much of the work done by machines as hereinbefore constructed is defective. 5

It is the primary object of the present invention to provide a thread-controlling mechanism designed to draw through the eye of the needle a length of thread for the purpose of preventing the skipping of stitches during the 10 formation of the knot-tying stitches at the end of a button-sewing operation. Stated in other words, the object of the present invention is the provision of means automatically operable during the formation of the knot-tying stitches at 5 the end of the sewing operation for producing a bight in the needle-thread between the needle-eye and the work-support, thereby to prevent the skipping of stitches.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations, and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the accompanying drawings, Fig. l is a side elevation of a button-sewing machine embodying the invention.

Fig. 2 is a front elevation of the sewing machine, showing the thread-controlling mechanism in retracted or ineffective position.

Fig. 3 is an enlarged perspective view of my improved thread-controlling mechanism, showing, in full lines, the thread-engaging element in retracted or ineffective position and, in dotted lines, in position in which maximum slack occurs.

Fig. 4 is a transverse sectional view through the work-clamp at the sewing point, showing the thread-engaging finger of the thread-controlling mechanism just as it engages the needlethread preparatory to pulling a length of thread through the needle-eye.

Fig. 5 is a view similar to Fig. 4, showing the thread-engaging finger in position in which maximum thread-drawing occurs.

Fig. 6 is a longitudinal sectional view through the work-clamp at the stitching point, illustrating the manner in which the needle, during the normal sewing operation, forms a loop in the needle-thread for entrance by the beak of the looper.

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Figs. 7 and 8 are longitudinal sectional views through the work-clamp at the stitching point of a machine not fitted with the present improvement at the respective times when the needlethread loop is correctly formed for entrance by the looper to'form the knot-tying stitch and when it is incorrectly formed, causing skipping of the stitch.

Fig. 9 is an enlarged front elevation of a portion of Fig. 8, partly in section, showing the way in which the needle-thread loop is incorrectly positioned rearwardly of the needle.

Fig. 10 is a longitudinal sectional view similar to Fig. 7 of a machine fitted with my improved thread-controlling mechanism, illustrating the manner in which the needle-thread loop invariably is correctly formed for entrance by the looper.

Referring to the drawings, the machine is constructed with a frame including a bed I from which rises a standard 2 of the overhanging bracket-arm 3 terminating in a head 4. The bed I includes an extension I of reduced width which constitutes a work-supporting arm.

The stitch-forming mechanism 15 constructed substantially in accordance with the disclosures in the U. S. patents to H. W. Morris, No. 1,606,173, and M. McCann, No. 1,941,481, dated Nov. 9, 1926 and Jan. 2, 1934, respectively, and comprises an endwise reciprocatory and laterally vibratory needle 5, rotary non-threaded looper 6, and looppositioner and needle-guide 6, all of which are actuated in the regular manner. The needle 5 is secured to the usual needle-bar I which is given its endwise reciprocatory movements by means of the link-connection 8 with the vibratory arm 9 fixed to the rock-shaft l0 actuated by the pitman-connection II from the eccentric l2 on the main-shaft I3.

The needle-bar is guided in its reciprocatory movements by upper and lower bearing blocks l4 and IS. The upper bearing block I4 is fixed to a pivot-stud [6 which is journaled in the head 4. The lower bearing block I5 is fixed to a pivotstud I! which is carried by the needle-bar-vibrating lever l8 fulcrumed on the adjustable block l9 and carrying a follower 20 entering the camgroove 2| in the needle-bar-vibrating cam 22 mounted on the upper end of the vertical feedshaft 23. The feed-shaft 23 makes only one complete rotation per complete button-sewing period and is driven by the worm-and-gear connection 24 with the main-shaft l3.

The work-holding means and the mechanism for imparting the required movement thereto are of common form, and are constructed substantially in accordance with the disclosure in the U. S. patent to M. McCann, No. 1,998,587, dated Apr. 23, 1935. The work-holder essentially comprises an arm 25 pivoted at 26 upon a carriage 21 mounted for endwise movement in suitable ways 28 on the bed I. Attached to the forward end of the arm 25 are two late: ally separable buttonengaging jaws 29 which grip the button and correctly position it relative to the reciprocatory needle 5. As clearly illustrated in Figs. 1 and 2, the work-holder is fitted with a button-spacing member 30 which is identical in construction with that disclosed in the above mentioned U. S. Patent No. 1,998,587.

As hereinbefore stated, the primary object of the present invention is the provision of a novel thread-controlling mechanism which improves the sewing characteristics of the machine. This mechanism preferably comprises an oscillatory thread-engaging finger 3 I, the upper end of which is clamped upon one end of a rock-shaft 32 journaled in hearings in the brackets 33 and 34. The bracket 33 is secured to the head 4 by the screws 35, while the bracket 3d is secured to the standard 2 by the screws 36. The rearward end portion of the rock-shaft 32 is preferably bent to the left of its axis of movement to provide, in effect, a rock-arm, designated as 31. Mounted upon the rock-arm 31 is a cam-follower 38 which is secured in correct position by the set-screw 39. The camfollower is preferably adjustably secured upon the rock-arm in order that the proper timing of the thread-controlling mechanism may be effected.

As will be observed from Figs. 1 and 3, the cam-follower 38 is normally held in contact with the under surface of the needle-bar-vibrating cam 22 by the spring 40 which acts between the rock-arm 3'! and the standard 2. In order to impart an oscillatory movement to the thread-wiping finger 3|, thereby to move it across the needle-path, the needle-bar-vibrating cam 22 has secured thereto upon its under surface, preferably by screws 4I, a suitably formed cam-lobe 42 which engages the cam-follower 38 and positively moves it into the dotted line position shown in Fig. 3. The effective surfaces of the camlobe and the cam-follower are preferably designed so that the thread-controlling action occurs during the last stitch-forming cycle only or, in other words, during the time in which the knot-tying stitches are being formed. As will be seen in Fig. 4, the thread-engaging finger is moved into position to just engage the needle-thread T as the needle 5 starts its descending movement or, in other words, as the final or knot-tying stitch-forming cycle begins. As the needle continues to descend and before it enters the threadhole in the button B (see Fig. 5), the thread engaging finger moves across the needle-path and draws through the eye of the needle a short length of thread given up by the usual take-up. When the needle enters the thread-hole in the button B, the thread T simply slips off the free end of the thread-engaging finger, which continues to move until it reaches its extreme righthand position. The thread-engaging finger remains in this position until the completion of the knot-tying stitch-forming cycle, after which it is returned to its inelfective position by the spring 40, (Fig. 2).

Following is a more detailed description of the operation of my improved thread-controlling mechanism. Referring to Fig. 6, it will be seen that during the normal button-sewing operation the laterally vibrating needle 5, as it starts to ascend, forms a thread-loop T below the worksupporting arm I, about which the previously formed thread-loop T engaged by the looper 6 will be subsequently cast. Since the laterally vibrating needle 5 alternately penetrates different thread-holes in the button B, during the normal sewing operation, practically no skipping of stitches occurs. However, when the needle repeatedly penetrates the same thread-hole in the button, as it does when forming the knot-tying stitches, the thread T is doubled upon itself at T (see Fig. 7), and this doubled portion of the thread T is held in the work by friction only. If the thread T reeves through the eye of the needle as the latter descends, the folded portion of the thread T is relatively short and is likely to be drawn down out of the work by the needle before the latter reaches the lowermost point;

of its stroke, as shown in Fig. 8. When this occurs the thread-loop T instead of being correctly formed transversely of the needle, as illustrated in Figs. '7 and 10, is frequently formed rearwardly of the needle, see Figs. 8 and 9, because of the fact that one limb of the thread-loop T extends from the previously formed stitches S in the work which are disposed rearwardly of the needle 5. Obviously, when the thread-loop T is formed rearwardly of the needle instead of transversely thereof, the advancing beak of the looper does not seize it and, consequently, no knot-tying stitch is produced. This defect has been largely overcome by employing a threadcontrolling mechanism which, during the knottying stitch-forming cycle, draws through the needle-eye a short length of thread which is being given up by the take-up, thereby increasing the amount of thread T between the needle-eye and the preceding stitch in the work. This increased amount of thread permits the formation by the needle 5 of a longer doubled thread-portion T see Fig. 10. The primary advantage of this longer thread-portion is that a fold is provided having an amount of thread in excess of that required by the needle as it descends through the work during the final stitch-forming cycle. Since the doubled thread-portion T is not completely drawn out of the work, the thread of the needle-loop T is constantly under control, inasmuch as one limb thereof is maintained in contact with the blade of the needle 5 and the loop T is formed transversely of the needle, in which position it is unerringly seized by the looper 6.

While in accordance with the provisions of the statute, I have illustrated and described my invention as applied to a button-sewing machine adapted for attaching four-hole buttons with a stay-button B to a body-fabric W by two parallel groups of stitches, it is to be understood that my improvement will function equally well on any other common type of button-sewing or tacking-and-barring machine. Furthermore, the invention is not to be understood as limited to the details of construction and relative arrangement of parts shown and described, as such details and relative arrangements may obviously be variously modified by those skilled in the art within the spirit of the invention.

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

1. In a sewing machine adapted to sew a predetermined number of stitches and then come to rest, the combination with a work-support and stitch-forming instrumentalities including a reciprocatory needle adapted to be vibrated during a portion of the stitching operation and operated in a fixed path during another portion of the stitching operation, of means located above the work-support and operable to produce a bight in the needle-thread to insure proper stitch-formation during that portion of the sewing operation in which the needle operates in a fixed path.

2. In a sewing machine adapted to perform a definite sewing operation, the combination with stitch-forming instrumentalities including a reciprocatory needle adapted to be vibrated during a portion of the sewing operation and operated in a fixed path during another portion of the sewing operation, of means operable only during the time in which the needle is operating in a fixed path to produce a bight in the thread to prevent the skipping of stitches.

3. A sewing machine adapted to sew a predetermined number of stitches and then come to rest, having, in combination, work-holding means, stitch-forming instrumentalities including a threaded reciprocatory needle, means for efiecting relative lateral movement between said work-holding means and said needle during a number of said predetermined stitches and for holding said work-holding means and said needle against relative lateral movement during other of said predetermined stitches, and means constructed and. arranged to form a bight in the needle-thread above said work-holding means to facilitate proper stitch-formation during that portion of the sewing operation in which there is no relative lateral movement between the work-holding means and the needle.

4. In a sewing machine, adapted to perform a definite sewing operation and then come to rest, work-holding means, stitch-forming mechanism including a threaded reciprocatory needle, means for effecting relative lateral movement between said work-holding means and said needle during a portion of said sewing operation and for holding said work-holding means and said needle against relative lateral movement during another portion of said sewing operation, and means operable only during the time in which there is no relative lateral movement between the work holding means and the needle for producing a bight in the needle-thread above said work-holding means to insure proper stitch-formation in that portion of the sewing operation.

5. A sewing machine adapted to sew a predetermined number of stitches and then come to rest, having, in combination, work-holding means, stitch-forming mechanism including a threaded eye-pointed reciprocatory needle and a cooperating loop-taker, means for efiecting relative lateral movement between said work-holding means and said needle during a number of said predetermined stitches and for holding said work-holding means and said needle against relative lateral movement during other of said predetermined stitches, and means automatically operated by said last-named means for drawing a length of thread through the eye of the needle.

6. In a sewing machine, the combination with work-holding means and stitch-forming instrumentalities including a reciprocatory needle, of means operable only during predetermined stitch-forming cycles to produce slack in the thread above the work-holding means to prevent the skipping of stitches during said predetermined stitch-forming cycles.

'7. A sewing machine having, in combination, work-holding means, stitch-forming mechanism including a reciprocatory needle and a cooperating loop-taker, means including a cam for controlling the distribution of the stitches in the work, and means operated by said cam for forming a bight in the thread.

8. A sewing machine having, in combination, work-holding means, stitch-forming mechanism including a threaded eye-pointed reciprocatory needle and a cooperating loop-taker, means including a cam for controlling the distribution of the stitches in the work, and means actuated by said cam for forming a bight in the thread, said last-named means including a thread-engaging finger, a shaft supporting said finger, and means carried by said shaft and engaging said cam.

9. In a sewing machine the combination with work-holding means and stitch-forming mechanism including an eye-pointed reciprocatory needle, of a thread-controlling mechanism comprising a thread-engaging finger, a shaft sup- UUlll porting said finger, and means for periodically actuating said shaft thereby to cause said threadengaging finger to draw through the needle-eye a length of thread.

10. In a sewing machine the combination with work-holding means and stitch-forming mechanism, of a threadcontrolling mechanism comprising a thread-engaging finger, a shaft supporting said finger, positive means for imparting movement to said thread-engaging finger in one direction, and impositive means for imparting movement to said thread-engaging finger in the opposite direction.

11. A sewing machine, adapted to perform a definite sewing operation and then come to rest, comprising a frame including a work-support and an overhanging arm, work-holding means, stitch-forming instrumentalities including a threaded eye-pointed reciprocatory needle, and means constructed, arranged and timed to engage the needle-thread above the work-support to draw through the eye of the needle before said stitch-forming instrumentalities complete said sewing operation a length of thread to be used in said sewing operation.

12. In a sewing machine, the combination with a work-support and stitch-forming instrumentalities including a threaded reciprocatory needle and a cooperating loop-taker, of means for repeatedly reciprocating said needle through the same needle aperture thereby forming in the work a doubled portion of thread, and means operable to insure that the length of thread comprising the doubled portion is of sufiicient length to prevent said doubled portion from being prematurely pulled out of the work during stitch-formation.

13. In a sewing machine, the combination with a work-support and stitch-forming instrumentalities including a threaded reciprocatory needle and a cooperating loop-taker, of means for repeatedly reciprocating said needle through the same needle aperture thereby forming in the work a doubled portion of thread, and means located above the work-support and operable to increase the length of thread forming the doubled portion so that the latter will not be prematurely pulled out of the work during stitch-formation.

14. In a sewing machine, the combination with a work-support and stitch-forming instrumentalities including a threaded reciprocatory needle and a cooperating loop-taker, of means for reciprocating said needle a plurality of times through the same needle aperture thereby forming in the work a doubled portion of thread, and means including a finger adapted to engage the thread between the work-support and the needle when the latter is out of the work to increase the length of thread forming the doubled portion so that said doubled portion will not be prematurely pulled out of the work during stitchformation.

MICHAEL McCANN.

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