US3347193A - Semi-dull finish bobbin case basket - Google Patents

Description

Oct. 17, 1967 N. PERRI 3,347,193

SEMI-BULL FINISH BOBBIN CASE BASKET Filed July 50, 1965 2 Sheets-Sheet l FIGZ.

N. PERRI Oct. 17, 1967 SEMI-BULL FINISH BOBBIN CASE BASKET 2 Sheets-Sheet 2 Filed July 30, 1965 United States Patent 3,347,193 SEMI-BULL FINISH BOBBIN CASE BASKET Nathan Perri, Northlake, Ill., assignor to Union Special Machine Company, Chicago, 111., a corporation of Illinois Filed July 30, 1965, Ser. No. 476,060 7 Claims. (Cl. 112--228) ABSTRACT OF THE DISCLOSURE This invention relates to lockstitch sewing machines and, more particularly, to improvements in the rotary hook assembly used in such machines.

Lockstitch sewing machines employing rotary hooks which rotate on a horizontal axis operate at high speeds in the neighborhood of 5000 stitches per minute and in some instances at higher speeds. When operating the sewing machine at these very high speeds, difliculties traceable to the rotary hook assemblies are encountered. The rotary hook, which travels around a stationary bobbin case is mounted, must take two revolutions to each forward movement of the sewing machine needle through the throat of the throat plate which means that the hook rotates 10,000 or more revolutions per minute.

Rotary hook assembles of the type herein referred to are disclosed, for example, in Covert and Schoij US. Patent No. 2,694,373, Nov. 16, 1954; and Attwood U.S. Patent No. 2,941,488, June 21, 1960. This type of rotary hook assembly is used in various lockstitch sewing machines, an illustrative example of such a sewing machine being disclosed in Covert US. Patent No. 2,977,910, Jan. 17, 1956.

A rotary hook assembly of the type mentioned above is mounted below the throat plate of the sewing machine and, as is well known, it comprises, in general, a stationary bobbin case removably mounted within a central opening of a surrounding bobbin case basket which in turn is mounted within a rotatable cup-like element which carries a loop engaging hook at its periphery. The hook directs the needle thread loop around the outside of the bobbin case basket in a manner that casts the loop around the bobbin thread. The bobbin thread travels from the bobbin spool within the bobbin case to the workpiece above the plate, the initial loop of the needle thread being caught by the rotating hook immediately after the needle has made its downward or forward stroke and has started back on its upward or retraction stroke. While the needle is continuing its upward stroke and while it is up, the rotary hook directs the needle thread loop around the outside surface of the bobbin case basket, casts the loop around the bobbin thread and the take-up means of the sewing machine draws the loop up and around the bobbin thread to make the stitch, while the rotary hook makes an idle revolution, ready to repeat the cycle to make a stitch upon the next reciprocating stroke of the needle, all in a manner well known.

The rotary hook assemblies heretofore available have been constructed of steel and of various alloys. Usually the bobbin case baskets have been plated or coated with a layer of wear resistant metal such as chromium. But

it is significant to note here that the parts or surfaces of the parts engaged by the loop thread during the operation of the heretofore available rotary hook assemblies were smooth and frequently they were polished to a mirrorlike finish.

One of the drawbacks of the hook assemblies heretofore available is that at a very high speed of operation of the sewing machine, there is a tendency of the thread loop to puff away at a terrifiic rate of speed immediately after the hook beak has passed the 6 oclock position of the rotary hook. As a frame of reference and for purposes of this discussion and description, it is assumed that the outer end of the rotary hook assembly is viewed as though one were looking at the face of a clock. During this puff away phase, the needle thread becomes utterly uncontrollable; the loop assuming a balloon type shape at the high speeds at which present day sewing machines are capable of operating. When then, an almost instantaneous increment of time later, the needle thread takeup mechanism on the sewing machine begins to rise with a rapid acceleration for the purpose of drawing up the needle leg of the thread loop to draw up the loop, a heavy and sudden jerk will be exerted on the ballooning thread loop, which produces an effect in the thread as does the sudden jerking on the end of a piece of loose rope. In such a case, the rope will start to whip and flutter, whereby a drag effect is created against the pull. A similar action is created in the thread loop when using prior art rotary hook assemblies at very high speed of operation of the sewing machine. This drag effect causes an untimely tension build-up in the needle thread in the direction of the needle thread supply and the previously set stitch in the line of stitching. As a result, thread is frequently drawn from the needle thread supply ahead of the proper time, causing loose stitch forming and pulling the loop up into the throat plate, and this prevents relaxed, uniform stitches and often causes the material of the workpiece being sewn to pucker in the zone of stitching.

Heretofore, there have been attempts made to overcome the unfavorable conditions in high speed operation mentioned above but with little, if any, success. One remedy has been to increase the thread tension but this results in unwanted puckering and frequent thread breakmg.

A principal object of this invention is to overcome the drawbacks of prior art rotary hook assemblies of the kind discussed above and to provide a rotary hook assembly which permits higher operating speeds while at the same time permitting operation at lower thread tension than prior rotary hook assemblies. This object is accomplished by providing a surface on the bobbin case basket which, instead of being smooth, is modified to have a finish consisting of minute indentations and elevations, the latter being leveled and smoothed off, as by bufl'ing, so that the surface is made up of minute contiguous rolling hills and valleys lying in random orientation and free of sharp peaks, jagged projections and sharp edges; and the surface has a semi-dull velvet-like finish.

A rotary hook assembly, made according to the invention, and as described in further detail hereinafter, reduces thread breakage, the check spring functions at the proper time and less check spring tension is required. The needle thread does not whip between the guiding eyelets. It permits the needle thread to be drawn from the thread supply at the proper time, that is, when the take-up is at the upper end portion of its stroke and when the stitch is being set in the fabric. And it produces relaxed, uniform stitches which reduces the likeli hood of the stitches causing the fabric material to pucker in the zone of stitching.

Although the novel features which are believed to be characteristic of the invention are pointed out in the annexed claims, the invention itself as to its objects and advantages and the manner in which it may be carried out, may be better understood by reference to the following more detailed description taken in connection with the accompanying drawings forming a part hereof, in which:

FIG. 1 is a front view of a rotary hook assembly constructed in accordance with the invention including, in section, the throat plate and supporting plate, the sewing machine needle and a workpiece being sewn;

FIG. 2 is a view partly in section looking from the rear to illustrate the movement of the needle thread loop when the loop reaches the 6 oclock position, this view being taken on a vertical plane behind the basket;

FIG. 3 is a view in perspective of the rotary hook assembly showing the needle. thread loop just before it is cast off;

FIG. 4 is a front view in elevation of the bobbin case basket having the velvet-like surface finish in accordance with the invention;

FIG. 5 is a plan view of the bobbin case basket shown in FIG. 4;

FIG. 6 is a view in perspective of the bobbin case;

FIG. 7 is a partial view in section greatly enlarged to illustrate the hills and valleys and the leveling off of the peaks of the hills on the surface of the bobbin case basket; and

FIG. 8 is a view in section of a detail.

The rotary hook assembly, illustrated in the drawings, is substantially the same in construction as that disclosed in the above mentioned Covert et al. U.S. Patent No. 2,694,373; but with this significant difference: the bobbin case basket, instead of being smooth and polished to a mirror-like finish, has been subjected to a particular sand blast treatment and to a buffing so that is surface has a semi-dull appearance and consists of minute indentations and elevations and the roughened surface has been buffed to remove any sharp peaks or jagged projections that may have been left on the surface of the elevations or hills after the sand blasting treatment.

Referring now to the drawings in which like reference characters indicate similar parts throughout the several views, the rotating component of the rotary hook comprises a generally cup-shaped spider member having a hub extension 21 secured by means of set screws 22 to the forward end of hook driving shaft 23. One end of the rim member 20a is provided with a forwardly and outwardly extending hook point portion or beak 24 which serves to seize and carry the needle loop in a manner to be described hereinafter. The inner surface of the rim of member 20 is provided with a raceway 36 for receiving the bobbin case basket rib or rail 25 and for guiding the rim portions of the rotary component 20 in its travel about the hook basket 40.One-portion of the raceway is provided by an overhanging or inturned lip 26 formed on detachable curved rim member 27 which is secured to the rim of the cup-shaped rotary component 20 by screws 28 (see FIG. 3). The end of the detachable member 27 adjacent hook point 24 is formed as a trailing thread guiding projection 29. Another portion of the raceway is formed by a 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 screws 31, is a guide plate 32 having one end thereof adjacent hook point 24 formed as a forwardly and inwardly extending pointed spur 33: spaced from the base of hook point 24 and affording a throat 71 for receiving needle thread loops seized by hook point 24. The throat 71 terminates in a pointed generally V-shaped crotch 72 which the loop thread engages as the hook point travels through an arc of about 180 after it seizes the loop. This spreads the legs LS and LN of the loop to assist in carrying it around the basket 40.

Plate 32 provides a needle loop engaging flange having an outer edge 34 curved generally outwardly from the hook point 24. The outer curved edge 34 guides the leg LS of the needle thread loop over the outer face of the bobbin case basket. The extremity of plate 32 is provided with a needle clearing notch 35 (FIG. 3).

The stationary component of the rotary hook assembly comprises a bobbin case basket 40, shown separately in FIGS. 4 and 5 and a bobbin case, shown separately in FIG. 6. A rotatable bobbin spool, not shown, is mounted in the hollow of the cylindrical portion 60, for rotation on a sleeve of the bobbin case which surrounds pin 44 of the basket 40.

Referring now particularly to FIGS. 4 and 5, the bobbin casebasket is formed with an angular, cup-like body member 42 provided at its bottom or inner end with a cross bar 43 arranged to support an axially disposed pin 44 extending from the inner to the outer end of the cupshaped member 42. Pin 44 is provided with an annular notch 45 adjacent the rounded outer end thereof. The notch 45 is indicated in FIG. 4 by the broken line circle. Bobbin case basket rail 25 is formed as an annular rib of the hollow body member 42 and is provided with a gap 26 (FIGS. 1 and 3) 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 thread around the bobbin case.

A radially extending flange 47 is formed at the outer end of the bobbin case basket and extends along approximately three quarters of the circumference thereof; a portion 54 positioned to the left of a retaining notch 48 and a portion 58 to the right of this notch, said portion 58 having cut out portions 37, 38, 39. Flange 47 is formed at the outer end of the bobbin case basket and the retaining notch 48 is adapted to mate with a lug or finger 49 mounted on bobbin case retainer bar 50 (FIGS. 1 and 3), in turn mounted on a screw post 50a fastened to the bed or frame of the machine. The lug 49 mating in the notch 48 serves to prevent the bobbin case 41 and bobbin case basket 40 from rotating with the rotary component of the hook assembly 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. 1) into the rotary hook assembly so that a needle loop may be formed upon the initial movement of the needle after the needle has reached the end of its downward stroke. The needle thread loop is picked up by hook beak 24, as is well known in the art.

As illustrated in FIG. 1, bobbin thread b emerges from the bobbin case, passes through an eyelet in the cylindrical wall of the bobbin case, then under a spring 75, and is guided by an inturned flange lug a and then passes through eyelet 53 mounted on the bobbin case. The bobbin thread b then passes upwardly across the radially extending faceof a portion 54 of flange 47 through the aperture 55 in throat plate 56 to the workpiece 79, where, together with the needle thread loop, the stitches are formed. When bobbin thread b becomes slack, as during a tacking operation, it is supported by peripheral face 57 of the portion 54 of flange 47 to the left of notch 48. By constructing portion 54 of the flange 47 with sufiicient 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 is this area, i.e., the radial width of portion 54 is preferably made sufliciently great that bobbin thread I) is carried upward along the outer radial face of said portion to a point above the path 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 sufliciently great that a minimum practical clearance between the inner. surface of flange 47 and hook point 24 is provided.

In FIG. 8, which is a cross sectional view through portion 54 of flange 47, it will be seen that bobbin thread b when slack, rests on peripheral face 57 in its path to the work and hence cannot fall into the path of hook point 24.

As has been indicated hereinbefore, the surface of the bobbin case basket 40 is not smooth, as in bobbin case baskets heretofore used, but the surface has been given a treatment that produces a surface that consists of minute elevations and indentations in the form of Contiguous minute hills and valleys in random orientation; the peaks of the hills being leveled off and any sharp or jagged projections and sharp edges being removed, as by a bufling operation, thus producing a surface having a semi-dull appearance and a hard but velvet-like feel. Further details regarding this surface and the manner of producing it are described later on herein.

The bobbin case 41, which is shown separately in FIG. 6, comprises a substantialy closed cylindrical body member 60 having a rear open end and a substantially closed outer end 61 from which projects inwardly a tubular axial post (not shown) which is adapted to fit on pin 44 of the bobbin case basket, the inner end of which engages an annular shoulder 62 (FIG. 4) at the base of pin 44. The axial tubular post of the bobbin case serves for rotatably mounting the bobbin spool thereon, within the cylindrical wall of body member 60.

The upper portion of the body member 66 is provided with a cut-out segment 63, which in the assembled rotating hook, is disposed below opening 51 and arranged to admit the needle 52.

Closed outer end 61 of body member 60 is provided with a pair of parallel undercut guide ribs 64, 64a 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 (FIGS. 1 and 5) thereby to hold the bobbin case within the central opening of the bobbin case basket. A lever plate 67, having an aperture 68, is hingedly mounted at one end thereof on one end of latch plate 65 so that when lever plate 67 is swung on its hinge, away from latch plate 65, the latch plate is disengaged from notch 45 in pin 44, permitting removal of the bobbin case 41 from the bobbin case basket 40. When the bobbin case is inserted in the bobbin case basket, a latch 60 (FIG. 1) located at one end of latch plate 65, engages the sides of a notch 70' in flange 47, thus preventing rotation of the bobbin case within the bobbin case basket.

A thread slit, not shown, in the drawing extends from the inner edge of body member 60 to an aperture in the cylindrical side wall of member 60, the aperture being hidden in FIG. 6 by a thread tension spring 75. Thread from the bobbin passes through the aperture in Wall 60 beneath spring 75, through a guide formed by inturned prong 75a of the spring along the outer surface of the wall of body member 60' and through self threading eyelet 53. The bobbin thread b then passes over the exposed portions of the flange 47 as described above. The eyelet is mounted in a recess portion 76 of closed end 61 (FIG. 6) by means of screw 77. The thread carrying portion of eyelet 53 fits into a recess 78 (FIG. 1) in portion 54 of flange 47. Recessing eyelet 53 in this maner permits passage of the needle thread around the front end of the bobbin case. Now it will be seen that bobbin thread b (FIGS. 1 and 3) is protected from hook point 24 by eyelet 53 and portions 54 and 57 of flange 47. Thus eyelet 53 and that portion of flange47 located on the left of notch 48 form a guarding means for the bobbin thread b which substantially eliminates breakage of the bobbin thread by the hook point or beak 24.

Referring again to the bobbin case basket, as shown in FIGS. 4 and 5, the shape and construction is of a standard type except that the basket does not have a smooth surface. It has a surface, which is accordance with the present invention, consists of contiguous minute hills and valleys in random orientation and free from sharp peaks, jagged projections and sharp edges. The preferred way of producing a bobbin case basket as illustrated in FIGS. 5 and 6 is to start with a standard basket made of steel that has been chromium plated in conventional mannear, the basket having a conventional smooth surface. This conventionally produced bobbin case basket was then subjected to a sand blasting treatment. The sand blasting material used was size 240 grit Flint-shot at an air pressure of 40 p.s.i. (pounds per square inch) and the particles were impacted against the surface until the chrome plating was substantially all removed; this requiring approximately one minute. This produced a surface on the basket which consisted of contiguous minute elevations and indentations in random orientation, and not of uniform sizes. Some of the peaks of the elevations were sharp and some of exposed edges were sharp or had minute jagged projections. The so roughened, sand blasted surface was then buffed on a soft bufiing wheel sufficiently to remove the jagged peaks and projections produced by the sand blasting. The bufling was carried out until the final finish of a roughness approximately 60-80 micro-inch (R.M.S.) was achieved. Reference is made to FIG. 7 which is a vertical cross section to greatly enlarged scale to illustrate the contiguous minute hills h and valleys v of varying sizes and distributed over the surface in random orientation and in which any sharp peaks have been leveled off by bufiing the surface after the sand blasting treatment. Such a surface resulting from the sand blasting treatment with fine sand or grit shot and thereafter subjected to bufling to produce a final finish having a roughness rating 60-80 micro-inches (R.M.S.) is herein, and in the claims, for purposes of convenience of description, referred to as a velvet-finish.

Operation of the rotary hook assembly will now be described and thereafter, data obtained from tests con ducted with the known or standard rotary hook assembly having a chrome plated smooth bobbin case basket, and tests conducted under like conditions with a rotary hook assembly, having a bobbin case basket having the velvetfinish above described; these tests showing the very material improved results attributable to the invention.

In operating the rotary hook, needle 52 descends through aperture 55 in throat plate 56 and through opening 51 into the upper portion of the bobbin case basket, which remains stationary. As the needle begins and then continues its upward or retraction stroke, a loop of needle thread is cast into the path of the rotating hook point 24, in a manner well known in the art. The needle thread loop is caught in the throat 71 and the thread engages the crotch 72 of the rotating component 20 of the assembly; this crotch spreading the legs LS and LN of the loop. The crotch, as it continues in its circular path of travel, carries the loop around the periphery of the basket in the arc to the left of notch of flange 47, as viewed in FIG. 1. When the crotch 72 reaches the 6 oclock position (at the bottom of the hook assembly) the loop is in a position, as illustrated in FIG. 2. As the crotch continues in its rotary path the loop is released from the crotch and the needle thread take-up mechanism on the sewing machine (which is not illustrated in the drawing) has begun to draw the excess needle thread upward at a rate exceeding the angular speed of the hook point 24. When the point 24 has reached the position illustrated in FIG. 3, the loop is caught on the projection 29 of member 20a and the leg LS has been guided inside the retainer arm 50 through notch 48 and finally the leg LN of the loop is drawn up and the loop, now around the bobbinthread b, is drawn up to form. the lockstitch 80. The rotary component 20 then makes an idle revolution after the needle thread is withdrawn therefrom, after which the stitch forming cycle than that of the conventional smooth, polished finish. Also, the raceway of the rotating component moves over the rail of the basket in a decidedly smoother manner than in conventional hooks. This is especially important is repeated to make the next stitch. at the moment when the front leg (LS in the drawings) The following Tables I and II show data obtained in is being pulled out of the basket retainer finger recess. tests to compare the operation of a conventional hook as- Although in the foregoing description only the bobbin sembly having a smooth surface bobbin case basket with case basket has been disclosed as having the surface the operation of a hook assembly, according to the inventreated to provide the velvet finish, it will be understood tion, having a velvet finish as described above. The tests that the face of the bobbin case may be treated to prowere conducted on the same sewing machine and the test vide a velvet finish. In fact, any surface of any part of hook assemblies were the same except for the differences the assembling where the part moves in contact with mentioned. Hooks identified in the tables as A and B and relatively to another or where the thread moves in were constructed according to the invention and hooks sliding contact with, a surface, improved operation may identified as C and D were conventional. be effected by providing the velvet finish thereon.

TABLE I Hook A Hook B Bobbin Check Needle Bobbin O..ec Needle Tension Spring Thread Tension Spring Thread (02.) (02.) (02.) (02.) (02.) (02,.)

% 1 2 1 2 M 1 M 1 $4 1 M 1 l4 1 M 1 M M 1 M 1 TABLE II Hook A H00 13 Bobbin Check Needle Bobbin Check Needle Tension Spring Thread Tension Spring Thread (02.) (02.) (02.) (02.) (02.) (02.)

70/2 Soft 1 3 l 3 3/0 Nylon 2 2 2-5 Nylon. M /2 1% 2 00 Nymm Unable to sew Unable to sew 000 Nymo Unable 5o sew Unable to sew In the above tables the size and kind of thread is shown, and the bobbin thread, check spring and needle thread tensions are shown. The data in each instance was taken after the sewing machine was operating at 5400 r.p.m. After each hook was installed and sewing with a good stitch, tacking ability, etc., a check was made of the bobbin thread tension, check spring, and needle thread ten- SlOl'l.

The data in the tables show that when using a 70/2 soft cotton needle thread, it required 3 oz. of needle thread tension on a machine equipped with a conventional hook, whereas only 2 oz. of needle thread tension was required to sew the same thread on a machine equipped with the hook constructed according to the invention. Also, it will be observed that when sewing synthetic threads (nylon, Nym-o), a much lower needle thread tension is required to sew the same synthetic threads on a machine equipped with a hook made according to the invention. This accounts for less thread breakage when using the hook assembly of the invention.

In the operation of the hook assembly provided by the invention, the thread loop when pulled around the 9 oclock position of the basket encounters less frictional resistance, and the thread loop, after passing through the 6 oclock position, does not putt and balloon away but stays rather close to the periphery of the basket, following same around in a gradual manner. Since the loop does not balloon out, the jerk of the rising take-up will not cause whipping or fluttering of the thread, and consequently, the unwanted drag effect, described in the foregoing, will not occur.

Furthermore, the velvet finish eliminates any sharp edges on the basket which is another friction reducing factor with regard to the thread loop. In other words, the

coefficient of friction of the velvet finish areas is less.

And, although the preferred method of producing the velvet finish is by a sand blasting treatment as described above, other methods of producing a light roughened finish may be employed, such, for example, as immersing I the part to be treated in a mineral acid such as hydrochloric or sulphuric, the time of immersion and concentration of the acid being adjusted to bring about the desired etching, after which the etched surface may be lightly buffed. Or the .part may be roughened in an electrolytic cell having positive and negative electrodes and containing a suitable electrolyte through which electric current is passed; the part to be roughened serving as anode. The amount of roughening can be controlled by adjusting the time and amount of current passing through the electrolyte or the desired velvet finish surface may be produced in other ways.

The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof,but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. A rotary hook assembly for a lockstitch sewing thread engaging flange adjacent to and guiding the needle thread lo'op over said face, guide means for guiding thread from said bobbin over said flange, said hook means carrying said needle thread loop around said bobbin case basket to loop it over said bobbin thread, the surfaces of said bobbin case basket which are engaged by said loop thread having a semi-dull finish consisting of contiguous minute hills and valleys in random orientation free from sharp peaks jagged projections and sharp edges and having a hard but velvet-like feel, said semi-dull finish being characterized by a coefficient of friction substantially less than that of a smooth, polished finish.

2. A rotary hook assembly according to claim 1 in which said surfaces have a roughness rating of 60-80 micro inches.

3. A rotary hook assembly for a lockstitch sewing machine comprising a cup-shaped rotary component having a rim portion mounting a needle thread loop engaging hook means rotatable in a circular path, said rim portion having a raceway on its interior surface, a bobbin case basket mounted in said cup-shaped rotary component, said basket having a generally cylindrically shaped wall, a bobbin case mounted within said basket, said basket having a vertically disposed portion at its rear end and a central opening at its front end and having a thread loop guiding flange at the front end of said cylindrical wall engaged by the loop thread during a stitching operation When said rotary component is rotated and said cylindrically shaped wall having an interrupted guide rail around its periphery, said raceway fitting over said guide rail and moving in contact therewith when said rotary component is rotated, the surface of said basket in those areas Where it contacts the needle loop thread and Where it engages said rotary component in frictional contact having a semi-dull finish and hard but velvet-like feel comprising contiguous, minute hills and valleys positioned in random orientation free from sharp peaks, jagged projections and sharp edges, the frictional resistance of said areas to the passing of said needle thread loop thereover being substantially less than that of a smooth, polished finish.

4. A rotary hook assembly for a lockstitch sewing machine comprising a cup-shaped rotary component having a rim portion mounting a needle thread loop engaging hook means rotatable in a circular path and having a raceway on the interior surface of said rim portion, a bobbin case basket mounted in said cup-shaped rotary component, said basket having a generally cylindrical shaped wall, a bobbin case mounted within said basket, said basket having a vertically disposed portion at its rear end and a central opening at its front end, said basket having a thread loop guiding flange at the front end of said cylindrical wall engaged by the loop thread during a stitch forming operation and said cylindrically shaped wall having an interrupted guide rail around its periphery, said raceway fitting over said guide rail and moving in contact therewith when said rotary component is rotated, the surface of said basket in those areas where it contacts the needle loop thread and where it engages said rotary component in frictional contact having a finish comprising contiguous, minute hills and valleys positioned in random orientation free from sharp peaks, jagged projections and sharp edges and having a roughness rating of 60-80 micro inches.

5. A bobbin case basket in a rotary hook assembly for a lockstitch sewing machine comprising a cup-shaped rotary component having a rim portion mounting a needle thread loop engaging hook means rotatable in a circular path and having a raceway on the interior surface of said rim portion, a bobbin case basket mounted in said cupshaped rotary component and a bobbin case therein, which bobbin case basket comprises a generally cylindrical shaped wall within which said bobbin case may be mounted, a vertically disposed rear Wall portion at the rear end of said cylindrical wall and a central opening at its front end, said basket having a thread loop guiding flange at the front end of said cylindrical wall engaged by the loop thread and said cylindrically shaped wall having an interrupted guide rail around its periphery adapted to fit into said raceway in frictional contact therewith when said rotary component is rotated, said basket having a finish over its interior and exterior surfaces comprising contiguous, minute hills and valleys positioned in random orientation buffed sufliciently to be free from sharp peaks, jagged projections and sharp edges, and having a hard but velvetlike feel, said finish being characterized by a coefiicient of friction which is substantially less than that of a smooth, polish finish.

6. A bobbin case basket in a rotary hook assembly for a lockstitch sewing machine comprising a cup-shaped rotary component having a rim portion mounting a needle thread loop engaging hook means rotatable in a circular path and having a raceway on the interior surface of said rim portion, a bobbin case basket mounted in said cup-shaaped rotary component and a bobbin case therein, which bobbin case basket comprises a generally cylindrical shaped wall within which said bobbin case may be mounted, a vertically disposed rear wall portion at the rear end of said cylindrical wall and a central opening at its front end, said basket having a thread loop guiding flange at the front end of said cylindrical wall engaged by the loop thread during a stitch forming operation and said cylindrically shaped wall having an interrupted guide rail around its periphery, and adapted to fit into said raceway in frictional contact therewith when said rotary component is rotated, said basket having a sand-blasted finish over its interior and exterior surfaces comprising contiguous, minute hills and valleys positioned in random orientation buffeed sufiiciently to be free from sharp peaks, jagged projections and sharp edges to provide a semi-dull, velvet finish which is less resistant to the passage of said needle loop thread thereover and in contact therewith than a smooth, polished finish.

7. A bobbin case basket in a rotary hook assembly for a lockstitch sewing machine comprising a cup-shaped rotary component having a rim portion mounting a needle thread loop engaging hook means rotatable in a circular path and having a raceway on the interior surface of said rim portion, a bobbin case basket mounted in said cup-shaped rotary component and a bobbin case therein, which bobbin case basket comprises a generally cylindrical shaped wall within which said bobbin case may be mounted, a vertically disposed rear wall portion at the rear end of said cylindrical wall and a central opening at its front end, said basket having a thread loop guiding flange at the front end of said cylindrical wall engaged by the loop thread during a stitch forming operation and said cylindrically shaped wall having an interrupted guide rail around its periphery, and adapted to fit into said raceway in frictional contact therewith when said rotary component is rotated, said basket having a sand-blasted finish over its interior and exterior surfaces comprising contiguous, minute hills and valleys positioned in random orientation buffed sufliciently to be free from sharp peaks, jagged projections and sharp edges and having a hard but velvet-like feel and a roughness rating of 60-80 micro inches.

References Cited UNITED STATES PATENTS 1,610,927 12/1926 Butler 51-319 1,697,810 1/1929 Comstock 51-319' X 2,694,373 11/1954 Covert 112228 X 2,941,488 6/1960 Attwood 112-228 2,977,910 4/1961 Covert 112256 PATRICK D. LAWSON, Primary Examiner.

HERBERT F. ROSS, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,347,193 October 17, 1967 Nathan Perri It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 32, after "case" insert basket in which the bobbin case column 6, line 6, for "is" read in columns 7 and 8, TABLE II, in the headings, for Hook A" and "Hook B" read Hook C and Hook D same TABLE II, second and third columns, line 5 thereof, for 50" read to column 10, line 20, for "cup-shaaped" read cup-shaped Signed and sealed this 22nd day of April 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. A ROTARY HOOK ASSEMBLY FOR A LOCKSTITCH SEWING MACHINE COMPRISING A HOLLOW CUP-SHAPED ROTARY COMPONENT HAVING A RIM INCLUDING A NEEDLE THREAD LOOP ENGAGING HOOK MEANS ROTATABLE IN A CIRCULAR PATH, A STATIONARY BOBBIN CASE BASKET HAVING A CENTRAL OPENING AND MOUNTED WITHIN SAID CUP-SHAPED ROTARY COMPONENT, A BOBBIN CASE ENCLOSING A ROTATABLE BOBBIN MOUNTED IN SAID CENTRAL OPENING, SAID BOBBIN CASE HAVING A FACE PORTION, SAID BOBBIN CASE BASKET HAVING A PERIPHERALLY EXTENDING LOOP THREAD ENGAGING FLANGE ADJACENT TO AND GUIDING THE NEEDLE THREAD LOOP OVER SAID FACE, GUIDE MEANS FOR GUIDING THREAD FROM SAID BOBBIN OVER SAID FLANGE, SAID HOOK MEANS CARRYING SAID NEEDLE THREAD LOOP AROUND SAID BOBBIN CASE BASKET TO LOOP IT OVER SAID BOBBIN THREAD, THE SURFACES OF SAID BOBBIN CASE BASKET WHICH ARE ENGAGED BY SAID

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