US1995278A - Rotary hook and bobbin-case device for sewing machines - Google Patents

Description

March 19, 1935. c. A. KESSLER ROTARY HOOK AND BOBBIN CASE DEVICE FOR SEWING MACHINES Filed May 12, 1934 2 Sheets-Sheet 1 March 19, 1935.

c. A. KESSLER} ROTARY HOOK AND BOBBIN CASE DEVICE FOR SEWING MACHINES Filed May 12, 1954 2 Sheets-Sheet 2 M, MW m w Patented Mar. 19, 1935 UNITED STATES ROTARY HOOK AND BOBBIN-OASE DEVICE FOR SEWING MACHINES Charles A. Kessler, Plainfield, N. J., assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application May 12, 1934, Serial Nd. 725,282

A 12 Claims. (01.112-228) This invention relates to. rotary hook and bobbin-case devices for sewing machines and more particularly to cup-shaped rotary hooks of the horizontal axis type making a plurality of rotations to one reciprocation of theusual sewing machine needle and having a loop-seizing beak arranged to cast the work-limb of the seized needle-loop in front of the rim of the hook-body and the take-up limb of the seized needle-loop in rear of the bobbin-case within the hook-body; a hook of this type being disclosed in the patents to Diehl et al., No. 1,125,669, dated Jan. 19, 1915, and No. 1,149,504, dated Aug. 10, 1915.

A rotary hook of the type in question is provided with a circular raceway in which is journaled the peripheral bearing rib of a substantially cylindrical bobbin-case restrained -by suitable means against rotation with the hook proper. The'bobbin-case carries a bobbin of thread and the function of the rotary hook is to seize a loop of thread from the sewing machine needle, draw out-or expand such loop and cast it about the bobbin-case, after which the usual needlethread take-up comes into action to draw the loop up to the work and complete the stitch;

There are certain aims in the construction of a rotary hook and bobbin-case device which are well recognized as being desirable of accomplishment. For example, to avoid chafing of the needle-thread caused by the reeving of ,an excessive length of such thread through the eye of the needle and to keep the stroke of the usual vibratory take-up as small as possible, it is desirable that the size or diameter of the rotary book be comparatively small so that it will not draw out a large needle-loop. Nevertheless, to avoid the necessity of frequent replenishment of the bobbin -thread supply, it is desirable that the bobbin-case be as large as possible, both in diameter' and length, and that waste. space between the bobbin-cavity in the bobbin-case and the inner wall of the rotary hook be reduced as much as possible.

It is'a recognized fact that the larger the bobbin, both in diameter and length, within a rotary book of .given size, the greater is the difiiculty of providing for the spreading or expansion of the needle-loop so that it may be freely cast about the bobbin-case. Excessive impedance by the bobbin-case of the casting of the thread-loop thereabout, necessitates the application of an excessive tension to the needlethread to prevent excessive wrapping of one or both limbs of the thread-loop circumferentially of the bobbin-case prior to the casting of the loop onto the outer and inner faces of the bobbincase, which circumferential wrapping of the thread unduly enlarges the needle-loop and steals thread from the supply, causing looping, a fault characterized by failure of the needle-loops to be drawn-fully up to the work by the take-up, particularly when the machine is operated at high speed.

The application of a heavy tension to the needle-thread to avoid looping greatly restricts the field of usefulness of the machine and limits it to the use of comparatively costly thread of high quality. A heavy tension also tends to untwist a thread drawn through it, and for this reason it has heretofore been exceedingly difiicult to provide a rotary hook mechanism which will sew thread of either direction of twist with equal facility at high speed.

The present invention has for an object to provide a rotary hook and bobbin-case device of the type disclosed in said Diehl et a1. patents which operates in conjunction with the usual reciprocatory needle, take-up and needle-thread tension-device to sew with needle-thread of poor quality and either direction of twist, and without looping, at higher speeds than'have heretofore been attained and without the application of a heavy tension to theneedle-thread.

A further object of the invention is to im prove the means for guiding and tensioning the bobbin-thread .to gain uniformity in the setting of the stitches regardless of speed or other variations in sewing conditions.

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, 1 is an outer or front face elevation of a rotary hook and bobbin-case device embodying the invention. Fig. 2 is an inner face view of the bobbin-case, with the rotary hook-body in section, showing a seized and partially expanded needle-loop just prior to the casting of the inner or take-up limb of the needle-loop off of the outer peripheral wall of the bobbin-case and over the inner peripheral edge of the bobbin-case onto the inner face of the latter. Fig. 3 is a view similar to Fig. 2 showing the inner or take-up limb of the needle-loop sion-carrying element of the bobbin-case.

-18 is a perspective view of the bobbin, and Fig.

after it has been cast off of the peripheral wall of the bobbin-case and onto the inner face of the latter. Fig. 4 is a perspective view of the hook and bobbin-case showing the inner or take-up limb of the needle-loop at the cast-on position relative to the bobbin-case. sembled perspective view of the two-part bobbin-case. Fig. 6 is an inner face view of that element of the bobbin-case which has a bearing rib journaled in the hook raceway. Figs. 7, 8 and 9am, respectively, sections on the lines 77, 8-8 and 99, of Fig. 6.

Fig. 10 is a section on the line 10-10, Fig. 8. Figs. 11 and 12 are side elevations of the bearingrib carrying element of the bobbin-case. Fig. 13 is a top plan view of the rotary hook in loopseizing position relative to the sewing machine needle. Fig. 14 is a fragmentary front face view of the bearing-rib carrying element of the bobbin-case. Fig. 15 is a section on the line 15-15, Fig. 14. Fig. 16 is a section on the line 16-16, Fig. 14. Fig. 17 is a perspective view of the ten- 19 is a longitudinal peripheral section through the bobbin-thread tension-device.

1 represents the reciprocatory needle of the conventional rotary hook sewing machine having the throat-plate 2 formed with the usual,

needle-hole 3 and feed-dog clearance slots 4. The machine has the usual horizontal hook-shaft 5 which makes two rotations to each complete reciprocation of the needle 1.

Mounted on the hook-shaft 5 is the cup-shaped hook-body 6 having a bobbin-case raceway 7 and cut away at one side to provide a loop-seizing beak 8 having an inclined loop-spreading inner edge 9 crossing the plane of the raceway 7 and preferably reversely curved at 10, 10 between the point of the hook-beak and the point where the inclined edge 9 crosses the plane of the raceway 7. This reverse curvature of the inclined loopspreading edge 9' permits the shortening of the point of the hook relative to the bottom 11 of the loop-casting throat 12, without making the point of the hook so blunt that it will not safely enter and seize the needle-loop, and without increasing the angle of inclination of the loop-spreading edge 9 in thatportion thereof adjacent the bottom 11 ofithe throat 12 which determines the width of spread of the seized needle-loop and must be suflicient to carry the inner limb e of the needle-loop onto the chamfer 31 to be described. 'In the present instance the angle 9 between the hook point and the bottom 11 of the loop-casting throat 12 is less than 30; affording an exceptionally short hook. By shortening the hook it is possible to advance the timed position of the hook on the shaft 5 and thus secure an earlier casting of the needle-loop about the bobbin-case, giving more time for the take-up to act to draw the thread-loop up to the work.

Journaled in the hook-raceway '7 is the peripheral bearing rib 13 of the cup-shaped bobbincase element 14 which has an outer cylindrical wall 15 carrying the bearing rib l3 and bridging the usual .gap formed in the rib 13 to provide the well known loop-detaining spur 16. The bobbincase element 14 has at the outer edge of its rim a flange 17 having in its outer or front face a rotation-restraining notch 18 entered by a tongue 19, Fig. 1, on the usual rotation-restraining bar 20 of the sewing machine. The flange 17, Figs. 14; 15 and 16, is formed adjacent the notch 18 with a bobbin-thread guiding slot 21 which is Fig. 5 is a disas.

separate and distinct from the rotation-restraining notch 18 and has an inclined bottom 22, Fig. 16, leading upwardly and outwardly from a point well within the inner cylindrical wall 23 of the bobbin-case element 14.

The bobbin-case element 14 has an open inner face crossed by a diameter bar 24 supporting the usual center stud 25 having at its free end a locking groove 26 for the usual spring-pressed latch-slide 27 of the mating bobbin-case element 28 carrying the bobbin 29 and the bobbin-thread tension device 30, to be described.

An important feature of .the present bobbincase resides in the chamfer 31 adjacent the inner edge 32 of the bearing-rib-carrying element 14 of the bobbin-case, in that region within the first 150 past the loop-seizing position of the hook, which chamfer provides a sharply defined needle-loop cast-on corner 33 beginning approximately at the angular position a, Fig. 6, which is preferably about 60 past the vertical position v and extending in the direction of rotation of the hook-body; said corner being preferably gradually inclined toward the inner edge 32 of the bobbin-case to a point about 120 past the vertical and then sharply or abruptly inclined at 0, toward said inner edge 32' with which said corner merges in the general direction of rotation of the hook-body 6. To provide the abruptly inclined portion 0 of the cast-on corner 33, the chamfer 31 preferably terminates in a concave portion d, Fig. 10, ground on a radius r, of approximately the radius of the bobbin-case and at an angle of approximately 45 to the inner wall 23 of the bobbin-case element 14, as shown in Fig. 8. The concave terminal portion d of the chamfer and the abruptly inclined terminal portion c of the cast-on corner 33 are preferably disposed in the region of approximately 120-l30 past the vertical.

The chamfer 31, at its beginning end, at about the angular position a, Fig. 6, is at an angle of about or somewhat less, to the inner cylindrical wall 23 of the bobbin-case element 14. From this point on the angle of the chamfer is gradually increased until the concave terminal portion d is reached, where the angle of chamfer is preferably about The abruptly inclined terminal portion 0 of the cast-on corner 33, as shown in Figs. 2, 3 and 4, is engaged by the inner or take-up limb e of the needle-loop after such loop has been well drawn out by the rotary-hook and suddenly casts such limb over the inner edge of the bobbin-case and onto the inner face of the latter. This caston action occurs rather suddenly while the hook is traveling the relatively short distance between the positions shown in Figs. 2 and 3 and is helped by the fact that the take-up limb e, of the needleloop is sliding longitudinally of itself peripherally of the bobbin-case, Fig. 2, and is thus more easily directed inwardly of the bobbin-case by the inclined cast-on corner 33, without reeving over the latter. At the time the cast-on action occurs, the needle-loop is well drawn out but not fully expanded and the amount of thread additionally required to cast the loop about the bobbin-caseis about equal to that additionally pulled off by the initial wrapping of the inner limb e of the needle-loop peripherally of the bobbin-case, as shown in Fig. 2, before such limb e encounters the sharply inclined portion d of the cast-on corner 33. e

The inclined loop-spreading edge 9 of the hook-beak is only required to spread the needleloop sufficiently to carry the loop into engagement with the loop-detaining spur 16 and thereafter lay the innerloop-lirnb e onto the beginning end of the chamfer 31. From this point on, the gradually inclined portion of the loopcaston corner 33 prevents the inner loop-limb e from wrapping around the cylindrical portion of the bobbin-case between the bearing'rib 13 and the chamfer 31. When the loop-limb e encounters the more abruptly inclined portion 0 of the cast-on corner 33 it is suddenly forced off of the chamfered portion 31 and is cast onto the inner face of the bobbin-case, as previously described.

The mating section 28 of the bobbin-case is also cup-shaped, as shown in Fig. 1'7, and hasin its rim an inclined thread-slot 34 terminating under the tension-spring 30 in a short peripherally extending portion 35 beyond which is a clearance slot 36 .for the downturned free end 37 of the tension-spring 30 which has a threadguiding or delivery slot 38 arranged to deliver the bobbin-thread to the bottom of the groove 21 in the bobbin-case element 14, without exposing the bobbin thread at any point below the top of the bobbin-case to the wiping action of the outer limb 1 of the needle-loop. Such wiping action has heretofore prove-d troublesome as it tends to displace the bobbin-thread and carry it into the rotation-restraining notch 18 where it interferes with the free escape of the needleloop.

The tension-spring 30 has the usual fastening screw 39 and tension-adjusting screw 40 and is formed at its free end within the thread-delivery slot 38 with an inwardly depressed transverse rib 41 which presses upon the bobbin-'- thread at a predetermined and fixed point for all adjustments of thetension-spring and tensions the bobbin-thread more uniformly for a given adjustment, in accordance with the principlesv disclosed in the Barron Patent No. 1,879,023, of Sept. 27, 1932.

The invention is not to be understood as limited to the details of construction and relative arrangements and proportions of parts of the preferred embodiment thereof shown and described, as modificationsthereof may obviously be made by those skilled in the art within the spirit and scope of the invention.

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

l. A horizontal-axis cup-shaped rotary hook for sewing machines having a loop-seizing beak and a raceway, a substantially cylindrical stationary bobbin-case having a peripheral bearing rib journaled in said raceway, said bearing rib having a gap therein providing a stationary spur at a point beyond the loop-seizing position of the hook-beak to detain the needle-loop seized by the hook-beak while the hook in its continued movement draws out the needle-loop for passage about the bobbin-case, the substantially cylindrical Wall of said bobbin-case being chamfered adjacent the inner edge of the latter to provide a cast-on corner inclined toward and meeting the inner edge of said bobbin-case in the general direction of rotation of said hook.

2. A horizontal-axis cup-shaped rotary hook for sewing machines having a loop-seizing beak and a raceway, a substantially cylindrical stationary bobbin-case having a peripheral bearing rib journaled in said raceway, said bearing rib having a gap therein providing a stationary spur at a point beyond the loop-seizing position of the of the inhook-beak to detain the needle-loop seized by the hook-beak while the hook in its continued movement draws out the needle-loop for passage about the bobbin-case, the substantially cylindrical wall of said bobbin-case being chamfered adjacent the inner edge of the latter to provide a cast-on corner inclined toward and meeting the inner edge of said bobbin-case in the general direction of rotation of said hook, the angle of the chamfer referred to the inner cylindrical wall of the bobbin-case being gradually increased from the beginning end of the chamfer toward the terminal point thereof.

3. A horizontal axis rotary hook for sewing machines having a cup-shaped body providedwith a loop-seizing beak arranged to cast the work-limb of a needle-thread-loop in front of the rim of the hook -body, a bobbin-case journaled in said hook and restrained against rotation therewith, said bobbin-case peripherally having a needle-thread-loop detaining spur and a cylindrical wall adjacent to said spur and extending inwardly of the hook-body, said cylindrical wall having within the width thereof a circumferentially extending cast-on corner spaced from said spur axially of the bobbin-case and terminating in the inner rim of the bobbin-case.

4. A horizontal axis rotary hook'for sewing machines having a cup-shaped body provided with a loop-seizing beak arranged to cast the work-limb of a needle-thread -loop in front of the rim of the hook-body, a bobbin-case journaled in said hook and restrained against rotation therewith, said bobbin-case peripherally having a needle-thread-loop detaining spur and a cylindrical wall adjacent to said spur and extending inwardly of the hook-body, said cylindrical wall having within the width thereof a sharply defined loop cast-on corner directionally extending circumferentially of the bobbin-case and merging with the inner edge of the bobbin-case in the general direction of rotation of the hook.

5. A horizontal axis rotary hook for sewing machines having a cup-shaped body provided with aloop-seizing beak arranged to cast the work-limb of the needle-thread-loop in front of the rim of the hook-body, a bobbin-case journaled in said hook and restrained against rotation therewith, said bobbin-case having a needle-loop detaining spur and a substantially cylindrical wall adjacent to said spur and extending in-- wardly of the hook-body, said wall having a circumferentially extending chamfered portion adjacent its inner edge terminating in a concave surface providing a needle-loop cast-on corner at the juncture of said concave surface with said cylindrical wall.

6. A horizontal axis rotary hook for sewing machines having, a cup-shaped body provided with a loop-seizing beak arranged to cast the work-limb of the needle-thread-loop in front of the rim of the hook-body, a bobbin-case journaled in said hook and restrained against rota-.

.tion therewith, said bobbin-case having a needleloop detaining spur and a substantially cylindrical wall adjacent to said spur and extending inwardly of the hook-body, said wall having a circumferentially extending chamfered portion adjacent its inner edge terminating within the region of approximately to past the vertical, to provide a needle-loop cast-on corner terminating in the inner edge of the bobbin-case within such region.

7. A horizontal axis cup-shapedrotary hook for sewing'machines having, a loop-seizing beak and araceway, a bobbin-case having a cylindrical bobbin-cavity coaxial with said hook and a circular bearing rib journaled in said raceway, said rib having a gap therein to provide a loopdetaining spur, said bobbin-case having a substantially cylindrical wall supporting said bearing rib and bridging the gap in the latter, the inner edge of the cylindrical wall of said bobbincase being chamfered in that region within the first 150 past the loop-seizing position of said rotary hook to provide a loop cast-on corner which is inclined from a point between the bearing rib and the inner edge of the bobbin-case toward and meets such inner edge in the general direction of motion of said rotary hook.

8. A horizontal axis cup-shaped rotary hook for sewing machines having, a loop-seizing beak and a raceway, a bobbin-case having a cylindrical bobbin-cavity coaxial with said hook and a circular bearing rib journaled in said raceway, said rib having a gap therein to provide a loop-detaining spur, said bobbin-case having a substantially cylindrical wall supporting said bearing rib and bridging the gap in the latter, the cylindrical wall of said bobbin-case being chamfered in that region of its inner edge within the first 150 past the loop-seizing position of said rotary hook to provide a loop cast-on corner which is inclined from a point between the bearing rib and the inner edge of the bobbin-case toward and meets such inner edge in the general direction of motion of said rotary hook, the point where said corner meets said inner edge being disposed in that region of the bobbin-case between 100 and 150 past the loop-seizing position of said rotary hook.

9. A horizontal axis cup-shaped rotary hook for sewing machines having, aloop-seizing beak and a raceway, a bobbin-case having a cylindrical bobbin-cavity coaxial with said hook and a circular bearingrib journaled in said raceway, said rib having a gap therein to provide a loop-detaining spur, said bobbin-case having a substantially cylindrical wall supporting said bearing rib and bridging the gap in the latter, the cylindrical wall surface which intersects the convex surface of the bobbin-casev to provide a sharply inclined continuation of said loop cast-on corner terminating at such inner edge.

10. A horizontal axis rotary hook for sewing machines having a cup-shaped body provided with a loop-seizing beak arranged to cast the work-limb of a needle-loop in front of the rim of the hook-body, a bobbin-case journaled in said hook and restrained against rotation therewith, said bobbin-case having a needle-loop detaining spur and a circular wall peripherally of which the take-up limb of the needle-loop is initially wrapped by the hook in its loop-casting excursion, said bobbin-case having means thereon constructed and arranged to cast said take-up limb off of said circular wall and onto the inner face .of the bobbin-case at a time such that the additional amount of thread pulled into the expanding needle-loop due to the initial peripheral wrapping of the take-up limb thereof about the bobbincase is approximately equal to the amount of thread additionally required by the hook subsequent to such time to cast the needle-loop about the bobbin-case.

11. The combination with a horizontal axis rotary hook having a loop-seizing beak and a loopcasting throat the bottom of which is angularly spaced less than 30 from the point of said beak, of a stationary cylindrical thread-case having a peripheral bearing rib journaled in said hook, said thread-case being chamfered adjacent its inner edge to provide a sharply defined needleloop cast-on corner between-said bearing rib and the inner edge of said bobbin-case, said cast-on corner extending peripherally of the bobbin-case and having a terminal portion abruptly inclined,

toward and meeting the inner edge of said bobbincase in the general direction of motion of said roformed with a rotation-restraining notch, said flange having a narrow thread-guiding slot out therein alongside said notch, said slot having a depth at its inner end exceeding the depth of said notch.

CHARLES A. KESSLER.

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