US2208999A - Locking thread supply case for sewing machines - Google Patents

Description

July 23, 1940. w T, MINETT 2208,999

LOCKING THREAD SUPPLY CASE FOR SEWING MACHINES Filed Feb. 28, 1938 wines; ,fin /enior" Patented July 23, 1940 UNITED STATES PATENT OFFICE LOCKING THREAD surety CASE FOR SEWING MACHINES New Jersey Application February 28, 1938, Serial No. 192,915

8 Claims.

The present invention relates to lockstitch sewing machines, and more particularly to improvements in thread cases for holding a supply of locking thread within a hollow 100p taker of the 5 rotary hook type, similar to that disclosed in U. 8. Letters Patent to Ashworth No. 1,169,909 of February 1, 1916, and to the present inventor No. 1,895,257 of January 24, 1933.

In the machines of the patents above referred to. a thread case of discoidal shape is provided and the needle loop, as it is passed about the thread case by the loop taker, frequently assumes an irregular position so that an excess of needle thread is required for smooth passage of the needle loop. To provide the required amount of needle thread in all circumstances, the motions of the other stitch forming devices and principally those of the take-up must be so adjusted that the needle thread will be given up at a to greater rate after a stitch is set than is required when the needle loop passes in a regular manner over the thread case. With the stitch forming devices so adjusted. the tension in the thread of the needle loop as it passes over the thread case 26 will increase when the loop assumes an irregular position on the thread case and the uniformity with which successive stitches are set in the work may be affected adversely. It has been observed that this difficulty is due at least in a 30 part to a failure of a needle loop to start its movement about the thread case, at a definite predetermined instant with respect to the movement of the loop taker and to that of the other stitch forming devices. Another factor which 85 contributes to the difficulty is the accumulation of wax, strands of thread and other particles within the space between the thread case and the loop taker in such a way that the movement of the needle loop will be retarded or jammed 40 between the loop taker and thread case.

The principal object of the present invention is to provide a novel and improved locking thread case for use within a loop taker of the rotary hook type, wherein the nedle loop does not pass I over the loop taker, so arranged that the difiiculties referred to are avoided, each needle loop being caused to pass over the thread case smoothly and uniformly without requiring the other stitch forming devices to give up an excessive l0 amount of needle thread and without the provision of excessively large clearance spaces between the thread case and the loop taker to avoid retarding or jamming of the needle loop from accumulation of wax or other matter.

I. With these and other objects in view. the lnvention is hereinafter described as embodied in a hook needle lockstitch sewing machine having a discoidal thread case formed with flat end and curved side surfaces, so arranged as to be held from rotation within the loop taker. of means on the side of the thread case for causing the needle loop to start its movement over the thread case uniformly when the loop taker reaches a predetermined angular position. In the form of the invention illustrated, the thread case has a relatively large thread holding capacity similar to that disclosed in inventors patent above referred to, and the means for starting the needle loop over the thread case consists of a thread guiding shoulder extending from a location on 16 the side of the thread case close to the path traversed by the tip of the loop taker beak to an end surface on the thread case.

The several features of the present invention and other advantages secured thereby will be readily understood by those skilled in the art from an inspection of the accompanying drawing and the following description.

Referring to the drawing. Fig. 1 is a view in ide elevation and partly broken away of portions of a lockstitch sewing machine embodying the loop starting shoulder of the present invention; Fig. 2 is a sectional plan view of the same parts of the machine; and Fig. 3 is an enlarged view of the loop starting shoulder on the thread case, shown in section, taken along the line 3-3 of Fig. 1.

The machine illustrated in the drawing is of substantially the same construction and manner of operation, except as hereinafter pointed out, as that disclosed in the patents referred to. The machine includes a curved hooked needle ID, a work support l2, a presser-foot H, a rotary loop taker i6, a thread case l8, and other stitch forming and work feeding devices. The loop taker 4o consistsiof a hollow cylindrical body having a rotary hook or beak, the tip 20 of which is-arranged to enter each needle loop, indicated at 21, after being opened by a loop spreader (not shown) and to carry each loop about the thread 5 case It. The loop taker is also formed with two guiding grooves or raceways 22 and 24 for rotatably supporting the loop taker in the machine frame and for supporting the thread case it within the loop taker, respectively.

The raceway groove 24 is engaged by a circular flan e 26 on the side surfaces of the thread case, the thread case being discoidal in shape with cyliggrical curving side surfaces between two subst tially flat end surfaces. One end of thethreadcaseisclosedwithanendwallfrom which there projects a stud 25 for receiving a wound bobbin or cop for the locking thread indicated at 28. The other end of the thread case is left open to provide access to the inside, the end surfaces of the side walls only being p sed. For holding the thread case from rotation with the loop taker, a pair of alternately reciprocating pins or fingers III are provided slidingly mounted in a fixed part of the machine and engaged by a rat trap spring 32 to'force the pins into slots at one end of the thread case, each pin being lifted to clear the needle loop as it passes across the open end of the thread case.

The tip 20 of the loop taker beak is so arranged that in engaging the needle loop and carrying it about the thread case it gives the needle loop a half twist, the loop being drawn forwardly of! the tip of the beak by the action of the take-up after the circuit has been completed. In this way the needle loop is passed about the thread case without passing entirely over the loop taker. To facilitate passage of the needle loop the axis of rotation of the loop taker is inclined towards the surface of the work and towards the rear of the machine. The thread case is almost completely enclosed within the hollow of the loop taker and, in order to provide space for a relatively large quantity of locking thread without increasing the outside diameter of the loop taker, the thread case is of such diameter as to fit closely within the hollow of the loop taker. One side of the needle loop 2|, as drawn by the loop taker beak, passes over the outside of the loop taker, and the other side into a space 34 provided by a cut-away portion of the thread case side wall between the ends of the raceway flange 26. The flange 26 has a hook or notch 21 at one end to assist the loop taker beak in separating the two sides of the needle loop and to hold from rotation with the loop taker that side of the needle loop within the opening 34.

In the machines of the patents, that side of the needle loop held within the opening 34 after being disengaged from the needle is caused to pass across the open end of the thread case and the other side of the needle loop is caused to pass across the closed end of the thread case. As the notched end of the flange is engaged by the needle loop, it sometimes is wound partway about the curved side surfaces of the thread case before it begins to move across the open end. When this occurs, more needle thread will be drawn by the loop taker as it passes the needle loop over the thread case than when the needle loop begins to pass across the open end of the thread case directly after the loop taker engages it. As a result, the other stitch forming devices must be so adjusted that the amount of needle thread available is sufllcient to allow the loop to pass over the thread case, even when it is wound about the curved side surfaces of the thread case, before starting across the open side. When the stitch forming devices are adjusted in this manner, if the needle loop starts across the open end of the thread case at once after the loop taker engages it, there will be a surplus of thread so that each stitcl. being formed will not be set withjthe same degree of tension or the needle thread as it extends along the surface of the work between stitches will not be drawn uniformly tight before the succeeding stitch is completed. 5

To cause the needle loop to begin its knovement across the open end of the thread caseihuniformly at a definite point, in accordance with I e present i f I invention, in the operation of the loop taker in carrying the needle loop about the thread case, the circular side wall of the thread case along the cut-away portion adjacent the notched end of the flange 28 is formed with an inclined and grooved or under-cut thread guiding shoulder 36 extending at an angle from the notched end of the flange 2G to the end surface of the side wall at the open end of the thread case. The inclination of the grooved shoulder 36 and the point along the end surface of the thread case at which the shoulder 36 terminates are so chosen that the needle thread, as the loop is first engaged by the loop taker, will lie smoothly within the groove of the shoulder, the shape of the groove being such that the thread is drawn towards the inside of the thread case away from the inside of the rotating loop taker. As soon as the loop taker reaches a position where the thread of the needle loop is carried above the end of the shoulder, the side of the needle loop begins to cross the open end of the thread case so that there is a definite predetermined movement of the needle loop as it is being passed around the thread case.

The groove in the shoulder 36, as more clearly illustrated in Figure 3, forms a sharpened edge 38 on the shoulder which acts not only to shift the thread away from the inside of the loop taker, but also to scrape on particles of wax, strands of thread, or other foreign substances which might tend to retard or jam the thread between the thread case and the loop taker. The inside of the loop taker, therefore, is kept clear and since the amount of thread required by the loop taker in the needle loop is uniform during each cycle, there is no necessity for providing an excess of thread during the passage of the needle loop about the thread case. The tension on the needle thread during successive stitches is thus kept more nearly uniform with the resultant advantages inuniformity with which the stitches are formed and set.

Having thus described the invention, what is claimed is:

1. A lockstitch sewing machine having, in combination with other stitch forming devices, a hook needle, a discoidal thread case having flat end surfaces'and a curved side surface, a loop taker for passing each loop of needle thread about the thread case without itself passing through the loop, means for holding the thread case from rotation with the loop taker, and means on the side surface of the thread case for causing one side of the needle loop to begin moving across an end surface of the thread case when the needle thread carried by the loop taker reaches a predetermined position with respect to the thread case.

2. A lockstitch sewing machine having, in combination with other stitch forming devices, a hook needle, a discoidal thread case having flat end surfaces and a curved side surface, a loop taker for passing each loop of needle thread about the thread case without itself passing through the loop, means for holding the thread case from rotation with the loop taker, and a thread guiding shoulder on the thread case extending from a location close to the path traversed by the tip of the loop taker beak to an end surface of the thread case for causing one side of the needle loop to begin moving across said surface when brought into engagement with the shoulder by the loop taker.

3. A lockstitch sewing machine having, in combination with other stitch forming devices. a

hook needle, a hollow rotary loop taker, a discoidal thread case having a flange along its curved side surface slidingly mounted within a raceway groove inside the loop taker and arranged with a notched end to separate the sides of the needle loop carried by the loop taker as the loop taker passes around the thread case, and a grooved thread guiding shoulder on the thread case extending from the flange to a point at one edge of the curved side surface of the thread case for causing one side of the needle loop to begin moving radially across the thread case at a predetermined position of the loop taker.

4. A lockstitch wax thread sewing machine having, in combination with the other stitch forming devices, a hook needle, a rotary loop taker having a circular hollow opening and a raceway groove inside the opening, a discoidal thread case having a circular flange rotatable within the groove in the loop taker and a curved side surface extending into the opening in the loop taker beyond the groove and fitting closely the inside of said opening, and means on the thread case beyond the flange for clearing the inside of the loop taker of material tending to jam between the thread case and the loop taker.

5. A lockstitch wax thread sewing machine having, in combination with the other stitch forming devices, a hook needle, a rotary loop taker having a circular hollow opening and a raceway groove inside the opening, a'discoidal thread case having a circular flange rotatable within the groove in the loop taker and a curved side surface extending into the opening in the loop taker beyond the groove and fitting closely the inside of said opening, and a sharp-edged the curved side surface being provided with a thread engaging notch positioned intermediate the end faces and having an inclined thread guiding shoulder extending from the notch to an end face to guide one side of the needle loop from the thread notch to said end face, and a loop taker for causing the needle thread loop to pass around the thread case.

'7. A discoidal locking thread case for lockstitch sewing machines employing a hooked needle, said thread case having end faces and a curved side surface therebetween, a thread engaging notch on the curved side surface, and a thread guiding shoulder extending from the bottom of the notch to one of the end faces.

8. A discoidal locking thread case for lockstitch sewing machines employing a hooked needle,said thread case having end faces and a curved side surface therebetween, an interrupted peripheral flange spaced from one of the end faces and terminating in a thread engaging notch, and an inclined, grooved thread guiding shoulder extending obliquely from the bottom of the notch to said end face and spaced radially inwardly of the flange.

WILFRID THOMAS MINETT.

Images