US2694373A

US2694373A - Rotary hook assembly

Info

Publication number: US2694373A
Application number: US294231A
Authority: US
Inventors: John N Covert; Schoij Edgar
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1952-06-18
Filing date: 1952-06-18
Publication date: 1954-11-16
Anticipated expiration: 1971-11-16
Also published as: DE1039815B; GB737721A

Description

Nov. 16, 1954 l J. Nl covERT Erm.

ROTARY Ho'ox ASSEMBLY s sheets-shet 1 Filed June 18, 1952 il., i

FIG. 3

INVENTORS. JOHN MOUVERT EDGAR SCHOJ ffbwwf/ ATTORNEY.

N0 16 1954 J. N. covERT :s1-AL ROTARY HOOK ASSEMBLY 3 Sheets-Sheet 2 Filed June 18, 1952 Nov. 16, 1954 J. N. cow-:RT ETAL ROTARY Hoox ASSEMBLY 5 Sheets-Sheet 5 Filed June 18, 1952 INVENToRs. JOHN N. covERT EDGAR scHow ATTORNEY States Patent @nice 2,694,373 Patented Nov. 16, 1954 ROTARY HOOK ASSEMBLY John N. Covert, Park Forest, and Edgar Schoij, Chicago,

Ill., assignors to Union Special Machine Company, Chicago, Ill., a corporation of Illinois Application June 18, 1952, Serial No. 294,231

7 Claims. (Cl. 112-181) The present invention relates to lockstitch sewing machines and more particularly to a novel and improved construction of the rotary hook assembly used in such machines.

In lockstitch sewing machines employing rotary hooks of the horizontal axis type, as heretofore constructed, it has been found that excessive breakage of the bobbin thread occurs whenever the bobbin thread becomes slack between the bobbin case and the work. This slack condition of the bobbin thread, which occurs occasionally during regular sewing operations, manifests itself particularly during tacking and similar operations wherein the work is not moved continuously in its usual direction. When the bobbin thread becomes slack, it tends to whip around across the path of the hook point and is frequently picked up by the hook point, jammed into the raceway and cut.

The principal object of the present invention has been to provide an improved rotary hook assembly of the horlzontal axis type wherein bobbin thread breakage due to slack bobbin thread being caught by the hook point is substantially eliminated.

A feature of the invention has been to provide an improved bobbin case and bobibn case basket or holder for a rotary hook of the above type which is so constructed as to minimize bobbin thread breakage.

Other and further objects and features of the invention will appear from the following description of a preferred embodiment of the same,

In accordance with the invention, the stationary cornponents of the rotary hook, which comprise the bobbin case and the basket or holder therefor, are provided w1th guard means for preventing engagement of bobbin thread slack by the loop engaging hook, the guard means comprising an eyelet mounted on the bobbin case and arranged to receive bobbin thread therefrom and to direct the bobbin thread generally toward the work and a needle thread directing flange formed on the bobbin case basket, the flange having a protecting extension disposed between the eyelet and the loop engaging hook, the protectmg extension having dimensions sufciently great to hold bobbin thread slack away from the loop engaging hook,

The invention will now be described in greater detail with reference to the appended drawings in which:

Fig. 1 is a plan View of a rotary hook assembly illustrating one embodiment of the invention and showing a conventional hook retainer;

Fig. 2 is a plan view of a portion of a rotary hook according to the invention and showing an improved hook retainer;

Fig. 3 is a front view of a rotary hook assembly constructed in accordance with the invention and showing the positions of the bobbin thread and needle loop relative to the hook point, throat plate and needle at a point in the cycle of operation of the machine;

Fig. 4 is a perspective view of a rotary hook according to the invention, at a later point in the cycle, showing the needle loop drawn upwardly from the beak of the hook and being pulled up between the bobbin case basket and the hook retainer in the course of forming a stitch;

Fig. 5 is a top view of the bobbin case basket of the hook. assembly; y

Fig. 6 is a front View of the bobbin case basket;

Fig'. 7 is a detail view, in vertical section, showing the relationship, in accordance with one embodiment of the 2 invention, between the bobbin thread, the bobbin case basket flange and the hook point.;

Fig. 8 lis a view similar to Fig. 7 illustrating how 'the bobbin thread may be engaged by the hook point 'in a conventional rotary hook; I

Fig. 9 is a perspective view of the bobbin case separated from the bobbin case basket;

Fig. l0 is a view o f the bobbin thread guiding eyelet detached from the bobbin case;

Fig. 11 is a plan view of a rotary hook illustrating a second embodiment of the invention; 'and Fig. 12 is a detail view, similar to Fig. '7, the second embodiment of the invention.

The improved rotary hook illustrated in the drawings is designed particularly for embodiment in lockstitch sewing machines of the high speed types illustrated in U. S. Patent 2,113,572, issued April l2, 1938, to N. V. Christensen 'et al. and in the U. S. 'patentapplication of George M. Reimer, Serial No. 150,843, filed March 2 1, 1950, now Patent No. 2,643,625, dated June 30, 1953. This improved rotary hook is not, of course, limited to use in these machines, but may advantageously be used in many similar machines.

Referring now to the drawings, the rotating compo'- nent of the rotary hook comprises a generally cup shaped spider member 20 having a hub extension 21V secured by means of s et screws 22 to the forward end of a hook driving shaft 23. One end of the rim of member 2t) is provided with a forwardly and outwardly extending hook point or beak 24 which serves to seize and carry the needle loop in a mannen to be described hereinafter, The inner surface of the rim of member -20 is provided with a raceway for carrying a bobbin basket rib or rail 25. One portion of the raceway is provided by an overhanging lip 26 formed on a detachable member 27 secured to the rim of spider member 20 by a number of screws of which screw 28 may be seen in Figs. 1 and 4. The end of detachable member 27 adjacent hook point 24 is formed as a thread guiding projection 29. Another portion of the raceway is formed bya lip 30 formed on the inner surface of the rim of member 20 adjacent the base of hook point 24. Mounted on the outside of the rim of member 20, on the opposite side thereof from detachable member 27, and fastened to member 20 by means of screws 31, is a guideplate 32 having one end thereof adjacent hook point 24 formed as a forwardly and inwardly extending spur 33 spaced from the base of hook point 24 and affording a throat for receiving needle thread loops seized by hook point 24.

Plate 32 provides a needle loop engaging flange havillustrating ing an outer edge 34 curved generally outwardly from hook point 24. The extremity of plate 32 remote from ggok point 24 is provided with a needle clearance notch The stationary component of the rotary hook comprises a bobbin case basket 40, shown separately in Figs. 5 and 6, and a lbobbin case 41, shown separately in Fig. 9

Referring now particularly to Figs. Sand 6, the bobbin case bsket is formed with an annular, cup-like body member 42 provided t the bottom or inner end thereof with a ros'sbar 43 arranged to support' an axiallydisposed pin 44. Pin 44 is provided with an annular notch adiacent the rounded outer end thereof and indicated in Fig. 6 by the dashed circle 45. Bobbin case baskety rail 25 is formed as an annular rib on the outer surface of body member 4 2 and is provided with a gap46 to facilitate withdrawal of the needle thread loop from the rotary hook. as will be described more fully hereinafter.l As was indicated above, rail 25 is ournaled in the hook raceway of the rotating' member of the rotary hook. The hook raceway is preferably made eccentric with respectto the rail 25 in such manner that lip 26 (Fig. 4) is' drawn away from the bobbin case basket 40 just in advance of its passage over the inner leg` of the needle thread loop, thus facilitating passage of the needle threadiaroundthe' bobbin case basket.

AV radially extendingilange 47 is formed at the outer end of the bobbin case basket and extends along approximately three quarters of the A circumference thereof,

Flange 47 is' provided with a retaining notch 48 adaptedv to mate with a lug 49 mounted on a bobbin case retainer linger 50 (Figs. 1, 2 and 4) and which serves to prevent the bobbin case and bobbin case basket from rotating with the rotary component of the hook during operation of the machine. Flange 47 is also provided with a needle opening 51 behind notch 48. Opening 51 is arranged to permit entrance of needle 52 (Fig. 3) into the rotary hook so that a needle loop may be formed, upon the initial upward movement of the needle, and picked up by hook point 24, as is Well known in the art As can be seen most clearly in Fig. 3, bobbin thread b emerges from the bobbin case through an eyelet 53 mounted on the bobbin case and passes upwardly across the outer, radially extending face of a portion 54 of flange 47 and through an aperture 55 in throat plate 56 into the work. When bobbin thread b becomes slack, as during a tacking operation, it is supported by the peripheral face 57 of the portion 54 of flange 47 (Figs. 4 and 5). It should be noted that portion 54 of flange 47 is to the left of notch 48 in the drawings. By constructing portion 54 of the flange 47 with sufcient radial width and circumferential extent and suflicient thickness, slack bobbin thread will be held by the radial and peripheral faces thereof so that such thread will not enter the path of hook point 24. The width of flange 47 in this area, i. e. the radial width of portion 54, is preferably nlade suciently great that bobbin thread b is carried upward along the outer radial face of said portion to a point above the plane of rotation of hook point 24. The thickness of portion 54 of flange 47, i. e., the axial width of surface 57, is preferably made suflciently great that a minimum practical clearance between the inner surface of flange 47 and hook point 24 is provided.

In Fig. 7, which 1s a cross sectional view through portion 54 of flange 47, it will be seen that bobbin thread b, when slack, rests on the peripheral face 57 in its path to the work and hence cannot fall into the path of hook point 24. In Fig. 8, which is a similar View of the corresponding elements of a conventional rotary hook, it can be seen how the slack bobbin thread is engaged by the hook point. Once engaged in this manner, the bobbin thread is carried into the raceway and severed by the relatively sharp edges of the raceway and the ribs of the bobbin case basket.

Bobbin case 41, which is shown separately in Fig. 9, comprises a substantially closed cylindrical body member 60 having a closed outer end 61 from which projects a tubular axial post (not shown) which is adapted to fit on pin 44 of the bobbin case basket and which rests on a shoulder 62 (Fig. 6) at the base of pin 44. The axial post carried the bobbin (not shown).

The upper portion of body member 60 is provided with a cut out segment 63 which, in the assembled rotary hook, is disposed below opening 51 and arranged to admit the needle 52 (Fig. 3).

Closed outer end 61 of body member 60 is provided with a pair of parallel undercut guide ribs 64 to which are fitted opposite edges of a spring pressed latch plate 65. Latch plate 65 is provided with an aperture 66, one end of which is adapted to mate with notch 45 of pin 44 (Fig. 6) thereby to hold the bobbin case within the bobbin case basket. is pivotally mounted at one end thereof on one end of latch plate 65 so that, when lever plate 67 is rotated away from latch plate 65, latch plate 65 is disengaged from notch 45 of pin 44, permitting removal of the bobbin case from the bobbin case basket. When the bobbin case is inserted in the bobbin case basket, a latch 69 (Figs. 3 and 4), located at one end of latch plate 65, engages the sides of a notch 70 in flange 47, thus preenlting rotation of the bobbin case within the bobbin case as et.

A thread slit, not shown in the drawing, extends from the inner edge of body member 60 to an aperture in the side wall of member 60, the aperture being hidden in Fig. 9 by a tension spring 75. Thread from the bobbin passes through the hidden aperture, along the wall of body member 60 beneath tension spring 75, through a guide formed by an inturned prong of tension spring 75, along the wall of body member 60 and into eyelet 53. The path of the bobbin thread after leaving eyelet 53 has been described hereinbefore in connection with Fig. 3.

As can be seen from Fig. 10, eyelet 53 is self-threading'. It is mounted on a recessed portion 76 of closed end A lever plate 67, having an aperture 68,.

61 (Fig. 9) by means of a screw 77. The thread carrying portion of eyelet 53 fits into a recess 78 (Fig, 6) 1 n portion 54 of flange 47. Recessing eyelet 53 1n thls manner permits easy passage of the needle thread around the bobbin case. It is evident, therefore, that bobbin thread b (Figs. 3 and 4) is protected from hook point 24 by eyelet 53 and by

portions

54 and 57 of flange 47.

y Thus eyelet 53 and that portion of flange 47 located on the left of notch 48 form a guarding means for the bobbin thread which substantially eliminates breakage of the bobbin thread by the hook point.

Operation of the rotary hook will now be described in connection with Figs. 3 and 4. Needle 52 descends through aperture 55 in throat plate 56 and through opening 51 (Figs. 1 and 5) into the upper portion of the bobbin case basket. As the needle begins to withdraw, a loop of needle thread n is cast into the path of hook point 24 in a manner well known in the art. The needle thread loop is seized by hook point 24 and 1s carried around the bobbin case basket by the hook point. It will be observed that the needle thread loop is first seized by hook point 24 when hook point 24 passes the plane of descent of the needle 52 adjacent notch 48. In

Vthe position shown in Fig. 3, the needle thread loop has been carried slightly more than around the bobbin case basket. As shown in Fig. 4, the needle thread take up mechanism (which is not illustrated in the drawing) has begun drawing the excess needle thread upward, drawing the end of the needle loop off hook point 24 and onto beak 29. It will be observed in Fig. 4 that that portion of the needle thread lop which passes across the front of the bobbin case basket is being drawn out between notch 48 and lug 49. When beak 24 reaches its uppermost position, the remaining needle thread is drawn upward by the take up mechanism. The needle thread loop, in its travel around the bobbin case basket, engages the bobbin thread to form a lockstitch as shown in Fig. 4. The rotating elements of the rotary hook make an idle revolution after the needle thread is withdrawn therefrom, after which the stitch forming cycle is repeated.

As was noted above, it is necessary for the needle thread to pass between lug 49 and notch 48. As shown in Fig. 2, lug 49 may be mounted on one end of a spring wire 49', the other end of the spring wire 49 being affixed in a suitable hole in finger 50. By employing the arrangement shown in Fig. 2, passage of the needle thread between lug 49 and notch 48 is greatly facilitated.

The rotary hook shown in Fig. 1l is substantially identical with the rotary hook of Fig. 1, except that wide portion 57 of Fig. 1 is replaced in the rotary hook of Fig. 11 by a relatively narrow portion 57. Support of slack bobbin thread in the arrangement of Fig. 1l is achieved by a wire guard 57 which may be mounted on the inner surface of flange 47 by welding or other suitable means. Wire guard 57" is preferably disposed in the same plane as surface 57' and extends axially inwardly substantially to the path of hook point 24, as in the case of portion 57 of Fig. 1. Fig. 12, which corresponds to Fig. 7, illustrates the way in which slack bobbin thread is supported by wire guard 57". It will be observed in Fig. l2 that substantially the same support is provided by the portion 57 and the wire guard 57 as isl provided in the previously described arrangement by portion 57.

While the invention has been described in particular embodiments thereof and in a particular use, it should not be understood as limited thereto, for obvious modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A rotary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing engagement of bobbin thread slack by said loop engaging hook comprising an eyelet mounted on said bobbin case and arranged to receive bobbin thread therefrom and to direct said bobbin thread generally toward the work, and a needle thread directing flange formed on said basket, said flange having a protectingA extension disposed between said eyelet and the path of said loop engaging hook and extending axially inwardly substantially to the path of said loop engaging hook with only working clearance in relation thereto, whereby said extension supports bobbin thread slack away from said loop engaging hook.

2. A roary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook arranged to rotate in a given path, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing engagement of bobbin thread slack by said loop engaging hook comprising an eyelet mounted on said bobbin case and arranged to receive bobbin thread therefrom and to direct said bobbin thread generally toward the work, and a needle thread directing ange formed on said basket, said flange having a protecting extension disposed between said eyelet and the path of said loop engaging hook, said extension being arranged substantially normal to said given path and extending axially inwardly substantially to said given path to provide only a working clearance in relation to said hook, whereby said extension supports bobbin thread slack away from said loop engaging hook.

3. A rotary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said basket having a needle thread opening in its periphery, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing engagement of the bobbin thread slack by said loop engaging hook comprising a needle thread directing flange formed on said basket, said ilange having a protecting extension disposed in the path of the bobbin thread from the bobbin to the work and said loop engaging hook, said protecting extension projecting axially to a vertical transverse plane inwardly of the outer edge of said needle thread opening and having dimensions sufficiently great to support bobbin thread slack away from said loop engaging hook.

4. A rotary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing enga ement of bobbin thread slack' by said loop engaging hoo comprising a needle thread directing ange formed on said basket, said ange having a protecting extension disposed in the path of the bobbin thread from f said bobbin case to the work and said loop engaging hook and extending axially inwardly substantially to the path of said loop engaging hook to provide only a working clearance therewith, whereby said extension supports bobbin thread slack away from said loop engaging hook.

5. A rotary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook, a stationary component journaled 1n said rotatable component and comprising a bobbin case ba'sket and a bobbin case disposed within said basket, said basket having a needle thread opening in its periphery, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing engagement of bobbin thread slack by said loop engaging hook comprising an eyelet mounted on said bobbin case and arranged to receive bobbin thread therefrom and to direct said bobbin thread generally toward the work, and a needle thread directing flange formed on said basket, said flange having a protecting portion thereof disposed between the thread delivering end of said eyelet and said loop engaging hook and extending axially inwardly to a vertical transverse plane which passes through said needle thread opening and substantially to the path of said loop engaging hook, whereby said portion of said flange supports bobbin thread slack away from said loop engaging hook.

6. A rotary hook for a lockstitch sewing machine, comprising a rotatable component including a needle loop engaging hook, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, and guard means for preventing engagement of bobbin thread slack by said loop engaging hook comprising an eyelet mounted on said bobbin case and arranged to receive bobbin thread therefrom and to direct said bobbin thread generally toward the work, a needle thread directing ange formed on said basket and a wire guard mounted on said flange at a portion thereof between said eyelet and said loop engaging hook, said wire guard extending axially inwardly substantially to the path of said loop engaging hook and having only a working clearance in relation thereto, whereby said flange and said wire guard support bobbin thread slack away from said loop engaging hook.

7. In a lockstitch sewing machine, the combination comprising a rotation restraining finger and a rotary hook comprising a rotatable component including a needle loop engaging hook, a stationary component journaled in said rotatable component and comprising a bobbin case basket and a bobbin case disposed within said basket, said bobbin case being arranged to supply bobbin thread from a bobbin therein to the work, a ange formed on said basket and having a notch therein adapted to mate with said rotation restraining linger thereby to prevent rotation of said stationary component with said rotatable cornponent, and a guard means for preventing engagement of bobbin thread slack by said loop engaging hook comprising said thread directing ange and an eyelet mounted on said bobbin case and arranged to receive bobbin thread therefrom and to direct said bobbin thread generally toward the work, said ange having a protecting extension disposed between said eyelet and said loop engaging hook and extending axially inwardly to a point inwardly of the part forming the base of said notch in said flange substantially to the path of said loop engaging hook whereby said extension supports bobbin thread slack away from said loop engaging hook.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,146,406 Diehl et al. July 13, 1915 1,988,789 Grieb Jan. 22, 1935 2,085,699 Kessler June 29, 1937 2,178,543 Rubel et al. Nov. 7, 1939