US3379150A

US3379150A - Loop takers for sewing machines

Info

Publication number: US3379150A
Application number: US630292A
Authority: US
Inventors: Ralph E Johnson
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1965-03-12
Filing date: 1967-04-12
Publication date: 1968-04-23
Anticipated expiration: 1985-04-23
Also published as: GB1078797A; CH455468A; US3386401A; DE1660986B2; DE1660986A1; GB1078796A; SE303420B; BR6677801D0; SE311269B; JPS5318934B1

Description

April 23, 1968 R. E. JOHNSON LOOP TAKERS FOR SEWING MACHINES Original Filed March 12, 1965 4 Sheets-Sheet VE N TOR. Ralph E Johnson AT ORNEY WITNESS April 23, 1968 R. E. JOHNSON LOOP TAKERS FOR SEWING MACHINES 4 Sheets-Sheet Original Filed March 12, 1965 R mm Y N M E R V 0 0 E h m Fm F 2 Y mm P 5 bm y M 2 N L l 8 m w 2 n April 23, 1968 R. E. JOHNSON 3,379,150

LOOP TAKERS FOR SEWING MACHINES Original Filed March 12, 1965 4 Shets-Sheet 5 I NVENTOR.

Ralph E. Johnson BY w i i- WA WITNESS April 1968 R. E. JOHNSON 3,379,150

LOOP TAKERS FOR SEWING MACHINES Original Filed March 1 1965 I 4 Sheets-Sheet 4 INVENTOR.

Ralph E Johnson WITNESS BY W 5W WT ORNEY United States Patent 3,379,150 L001 TAKERS FOR SEWING MAEIHINES Ralph E. Johnson, Boonton, N.J., assignor to The Singer glompany, New York, N.Y., a corporation of New ersey Original application Mar. 12, 1965, Ser. No. 439,420. Divided and this application Apr. 12, 1967, Ser. No.

3 Claims. (Cl. 112-228) ABSTRACT OF THE DISCLOSURE Cross reference to related application This application relates to a loop taker for a lockstitch sewing machine and is a division of my copending United States patent application Ser. No. 439,420, filed Mar. 12, 1965.

Summary 0 the invention It is an object of this invention to provide a novel circularly moving loop taker for a lockstitch sewing machine including a rotary loop taker body carrying the thread engaging beak, a bobbin case, and a stationary bobbin case retainer which provides the sole constraint for the bobbin case radially, angularly and axially of the loop taker body. This novel arrangement eliminates the necessity for the conventional bearing raceway between the loop taker body and the bobbin case and provides instead simply planar bearing surfaces of engagement therebetween. In addition to the advantage of cost reduction made possible by the simplicity of the loop taker construction of this invention the problem of thread jamming in the bobbin case raceway is obviated.

Description of the drawings One embodiment of the invention will be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a side elevational view of a sewing machine embodying a loop taker of this invention;

FIG. 2 is a vertical cross-sectional view of that portion of the sewing machine of FIG. 1 in the vicinity of the rotary hook taken through the axis of the rotary hook and illustrating the disposition of the sewing threads during work penetration by the needle;

FIG. 3 is a vertical cross-sectional view similar to that of FIG. 2 and illustrating the disposition of the sewing threads after being acted upon by the rotary hook;

FIG. 4 is a top plan view of the parts illustrated in FIGS. 2 and 3 with the sewing threads illustrated in the positions illustrated in FIG. 3;

FIG. 5 is a top plan view of the rotary hook and the surrounding portion of the sewing machine bed but with the work support and the bobbin and bobbin case removed;

FIG. 6 is a top plan view of the bobbin case showing the thread occupying the position illustrated in FIGS. 3 and 4 thereon and including fragments of the rotary hook;

FIG. 7 is a bottom plan view of the bobbin case showing the thread occupying the position illustrated in FIGS. 3, 4, and 6.

FIG. 8 is a vertical cross-sectional view similar to FIG.

3,379,150 Patented Apr. 23, 1968 2 and illustrating the disposition of the sewing threads shortly after seizure of a needle thread loop by a beak on the loop taker;

FIG. 8A is a top plan view of the rotary hook, bobbin, bobbin case and fragments of the sewing machine elements associated therewith in a position corresponding to that illustrated in FIG. 8;

FIG. 9 is a vertical cross-sectional view similar to FIG. 8 and illustrating the disposition of sewing threads as the needle thread loop is about to be cast off the rotary hook beak;

FIG. 9A is a top plan view of the rotary hook, bobbin, bobbin case and fragments of the sewing machine elements associated therewith in a position corresponding to that illustrated in FIG. 9;

FIG. 10 is a vertical cross-sectional view similar to FIG. 8 and illustrating the disposition of sewing threads as withdrawal of the needle thread loop from a stored position on the bobbin case is initiated;

FIG. 10A is a top plan view of the rotary hook, bobbin, bobbin case and fragments of the sewing machine elements associated therewith in a position corresponding to that illustrated in FIG. 10;

FIG. 11 is a perspective view of the top of the bobbin case; and

FIG. 12 is a perspective view of the bottom of the bobbin case.

Detailed description Referring to the drawings, the sewing machine incorporating a loop taker of this invention is assembled preferably on an integral frame indicated generally at 11 and including a horizontal base plate 12 from which extends a vertical standard 13. Secured beneath the base plate 12 as by a bracket 14 and screws 15 is an electric motor 16 having a shaft 17 extending vertically upward through an aperture 18 in the base plate.

A rotary hook indicated generally at 26 is secured as by a set screw 21 to the shaft 17. The rotary hook 20, the specific details of which will be described hereinbelow, is of generally cylindrical form and for protection of a sewing machine operator, is preferably arranged to turn with slight clearance within a bore 22 formed in a support pedestal 23 fixed as by screws 24 on the base plate 12. A top cover plate 25 seated in a shallow counterbore 26 in the pedestal 23 and secured to the pedestal by

screws

27 and 28 spans the hook accommodating bore 22 and also sustains a raised work supporting plate 29 formed with a needle aperture 30.

A bobbin case indicated generally at rests upon the rotary hook and is both located axially of the hook as well as constrained against rotation with the rotary hook by cooperative interengagement with the top cover plate 25 and with rotation restraining means on the pedestal 23 as will be described with greater particularity hereinafter together with the details of construction of the bobbin case. A thread carrying bobbin 41 is freely journalled in the bobbin case and held therein by a leaf spring 42 secured by the top cover plate fastening screw 28, which leaf spring also serves frictionally to resist turning movement of the bobbin so as to provide bobbin thread tension.

A shaft is journalled in the standard 13 and has secured to it a balance wheel pulley 51. An electric motor 52 is supported on a bracket 53 secured on the standard 13 and includes a motor shaft 54 having a pulley 55 fast thereon and drivingly connected as by a belt 56 to the balance wheel pulley 51. Turning movement of the shaft 50 serves to impart work penetrating endwise reciprocatory movement to an eye pointed thread carrying needle 57, to impart operative movements to a needle thread take up mechanism indicated generally at 58, and to operate a work feeding mechanism indicated generally at 59.

A bracket 60 secured by screws 61 to the standard sustains a spool pin 62 and a conventional needle thread tension device 63. These conventional parts are illustrated in FIG. 1 in dot and dashed lines so as not to obscure the other mechanisms of the sewing machine. The path of thread from a spool on the spool pin 62 proceeds to the tension device 63, to the needle thread take up mechanism 58 and thence to the eye of the needle 57.

The details of construction of the rotary hook 20, bobbin case 40 and associated mechanisms will now be described in detail.

The rotary hook is formed with a central hub 201 in which the set screw 21 is located and a cylindrical outer wall 202 merging with an inturned flange 203 at the top. The flange 203 is notched radially at intervals as at 204 to form inwardly directed thread seizing beaks 205 on the flange 203. The flange 203 may be formed with one beak 205 or with a plurality of beaks, stitching being possible using the principles of this invention with any number of beaks. As will be explained hereinafter with reference to the mode of operation of this invention, the number of beaks merely constitutes one factor which may influence the maximum practical speed of needle reciprocation relatively to the speed of rotation of the hook. In the preferred embodiment illustrated in the drawings, four hook beaks 205 are used and it is also preferable that the diameter of the flange 203 be gradually increased from each beak 205 to the next succeeding notch 204.

The central hub 201 of the rotary hook is formed with a raised boss 206 spaced inwardly of the outer wall 202 to define therebetween an annular recess 207 accommodat ing penetration of the needle 57. A frusto-conical upper extremity 208 is formed on the raised boss 206 which together with a circular recess 209 formed in the upper end of the raised boss defines a narrow annular land 210 facing upwardly and disposed at a level beneath that of the flange 203 in which the loop seizing beaks 205 are formed.

Referring to FIGS. 4 and 5, a crosspiece 212 is set into the top of the pedestal 23 and is secured by screws 213 so as to span a chord of the rotary hook accommodating bore 22. Secured by screws 214 to the crosspiece is a wire leaf spring 215 having a bowed free extremity 216 projecting beyond the crosspiece. The top cover plate 25 of the pedestal 23 is provided above the bore 22 with a generally rectangular aperture 217 formed with a step 218 adjacent to the needle aperture in the work supporting plate 29. The leaf spring extremity 216 and the step 218 engage the bobbin case to restrain the bobbin case from rotation and to locate the bobbin case relatively to the rotary hook.

The bobbin case 40 is formed with a planar bottom surface 221 from which rises a cylindrical sidewall 222 enclosing a cylindrical upwardly open bobbin accommodat ing cavity 223 formed concentrically with a cylindrical stud 224 terminating in an upstanding bearing boss 225 on which the bobbin is adapted to be journalled. Projecting radially from the cylindrical sidewall 222 of the bobbin case is a flange 226 which at its periphery rests on top of the rotary hook flange 203 as illustrated in FIGS. 2 and 3. The bobbin case flange 226 is parallel to and spaced from the bottom surface 221 of the bobbin case base so that the surface 221. rests upon the annular land 210 of the raised boss 206 on the rotary hook.

Above the projecting flange 226, the outer surface of the bobbin case sidewall 222 is tapered and frusto-conical in form so as to project through the top cover plate aperture 217 and slightly above the level of the top cover plate 25.

The bobbin 41 is formed with top and

bottom flanges

230 and 231 respectively which are preferably formed integrally with a hub portion 232 as illustrated in FIG. 2. The bottom flange 231 is formed with a counterbore 233 which loosely embraces the bobbin case stud 224 and the counterbore 233 terminates in a bore 234 which snugly accommodates the bearing boss 225 on the bobbin case stud 224. The leaf spring 42 bears against the top flange 230 of the bobbin and urges a depending peripheral rim 235 on the bottom flange 231 of the bobbin against the bobbin accommodating cavity 223 of the bobbin case frictionally to resist turning of the bobbin, and in addition the spring 42 urges the bobbin case flange 226 against the rotary hook flange 203 and the bottom surface 221 of the bobbin case against the annular land 210 on the raised boss 20.. of the rotary hook.

Referring to FIGS. 6, 7, l1 and 12, both the bobbin case sidewall 222 and the projecting flange 226 are cut away along a chord as indicated at 240 which chord faces the path of reciprocation of the needle 57 when the bobbin case is positioned on the rotary hook thus providing needle clearance. Preferably a bevel 241 is formed on the bobbin case base in the vicinity of the cut away portion 240 from the level of the flange 226 to the bottom surface 221 of the bobbin case. Above the level of the flange 226, the sidewall 222 of the bobbin case is vertically slabbed as at 242 substantially parallel to the chord along which the portion 240 is cut away to define a shoulder 243 engageable with the step 218 formed in the top cover plate aperture 217 for restraining rotation of the bobbin case. The bobbin case sidewall 222 adjacent to the shoulder 243 is formed with a vertical slot 244 through which bobbin thread passes to the needle aperture 30 in the work supporting plate.

The bobbin case sidewall 222 and the projecting flange 225 are also cut away as at 245 along a chord substantially parallel to the crosspiece 212 when the bobbin case is positioned on the rotary hook.

Referring to FIGS. 7 and 12 which illustrate the under side of the bobbin case 40, a shallow recess 250 is formed in the bottom surface 221 of the bobbin case. The recess 250 is partly circular in shape with a chord 251 preferably formed substantially parallel to the cut away portion 245 of the bobbin case sidewall. The recess 250 is preferably formed slightly deeper than the largest diameter of thread which may be handled by the sewing machine and thus the recess serves to provide clearance for movement of the thread between portions of the bobbin case 40 and the annular land 210 on the rotary hook. FIG. 6 includes in dot and dashed lines a representation of the position of the annular land 210 relatively to the bobbin case 40 when the bobbin case is in place on the rotary hook. In FIG. 7, the cross hatched area 210 in dicates that portion of the annular land 210 which engages the bottom surface 221 of the bobbin case.

Referring to FIGS. 2, 3, 6, and 11 the frusto-conical outer surface of the bobbin case sidewall 222 is formed near the rim and parallel to the flange 226 with a thread supporting shelf 260 which extends from the slabbed portion 242 adjacent to the path of reciprocation of the needle 57 approximately 180 about the rim of the bobbin case sidewall 222.

Operation With the bobbin case 40 in place on the rotary hook 20 and a bobbin 41 wound with thread B in place in the bobbin case cavity 223, the rotary hook may be set in motion by closing a toggle switch controlling the.

motor 16. .As mentioned heretofore, in the embodiment illustrated in the drawings the rotary book 20 will preferably be rotated at a substantially constant velocity and in counterclockwise direction as viewed in FIGS. 4, 5,8A, 9A and 10A. The bobbin thread B will not be influenced by the rotating beaks 205 since the bobbin case slot 244 1 through which the bobbin thread is directed to the needle aperture 30 is situated above the level of the bobbin case flange 226 which rests upon the rotating beaks 205.

In preparation for sewing, the needle 57 must carry a needle thread N preferably directed from a spool (not shown.) on the spool pin 62 through the needle thread tension device 63, then to a take up eyelet of the take up mechanism 58, and finally through thread guides 101 and the eye of the needle. Upon insertion of a work fabric beneath the presser and feeding

feet

135, 176, respectively the machine is in readiness to sew.

FIG. 2 illustrates the position of the needle and loop taker parts during work penetration of the needle 57 as influenced either by manually turning the balance wheel pulley 51 or by operator influence of a speed control unit 85 for the motor 52. During each work penetration, the needle 57 will move through a range of positions in which the needle thread N carried thereby will be positioned for possible seizure by a beak 205 of the rotary hook. Although the particular range of needle positions during which needle thread loop seizure by the hook beak is possible may vary depending upon many specific factors such as the particular kinematics of the needle reciproeating mechanism, the type of needle, for instance whether scarfed or not, and the condition and type of needle thread and work fabrics being used, for any given conditions, the particular range is identifiable.

Any of the hook beaks 205 traversing the path of reciprocation of the needle 57 while the needle occupies the thread loop presenting range of positions may seize the presented needle thread loop and carry the seized thread loop into a stored position on the bobbin case 40 as illustrated in FIGS. 3, 4, 6 and 7. FIGS. 8, 8A, 9 and 9A illustrate the manner in which any one of the hook beaks carries the needle thread loop into the stored position on the bobbin case. When seized by any of the hook beaks 205, one limb Ns of the needle thread loop will extend from that beak to the needle eye and the other limb Nw will extend from that beak to the needle aperture 30. Since both thread limbs Ns and Nw extend along chords spanning the circular path of the hook beaks 205, seizure of the needle thread loop by any other hook beak will be obviated. Once seized by any one of the hook beaks 205, that limb Nw of the needle thread loop which extends directly to the needle aperture 30 and to the stitches in the work fabric is carried upwardly through the space provided by the slabbed portion 240 on the bobbin case to the level of the shelf 260 on the bobbin case as illustrated in FIG. 8. That limb of the seized needle thread loop Ns which extends to the eye of the needle and thence to the needle thread supply is carried through the space provided by the slabbed portion 240 and across the underside 221 of the bobbin case.

FIGS. 9 and 9A illustrate the position of parts and of the threads as the hook beak 205 carries the needle thread loop on to the bobbin case 40. It will be noted that the thread limb Nw is deposited on the shelf 260 and the thread limb Ns is carried into the space between the annular land 210 on the rotary hook and the recess 250 in the undersnrface of the bobbin case which extends beyond the annular land 210 on that side from which the thread limb N3 is introduced. FIGS. 9 and 9A also illustrate that both thread limbs Ns and Nw are turned about the needle 57 as the thread limbs are drawn out by the hook beak 205. The fraction imposed by this turning about the needle coupled with the action of the bobbin case in spreading the thread loop by raising the limb Nw above the level of the hook beak and lowering the limb Ns below the level of the hook beak, draws the needle thread loop from the hook beak 205. As illustrated in FIG. 9A the needle thread loop is about to be drawn from the hook beak and as illustrated in FIGS. 3, 4 and 6, the needle thread loop has been drawn from the hook beak and on to the cut away portion 245 of the bobbin case sidewall out of the path of the hook beaks 205.

When the needle thread loop is drawn from the hook beak 205 into the stored position on the bobbin case as illustrated in FIGS. 3, 4 and 6, passage of the thread limb Ns beneath the bobbin case is blocked by that portion 210' of the annular land 210 on the rotary hook which, as illustrated in FIG. 7, engages the underside 221 of the bobbin case beyond the chord 251 of the shallow recess 250 therein.

Once deposited on the bobbin case the thread loop is stored in the sense that further influence by any of the hook beaks is obviated. Thereafter the thread loop is removable from the bobbin case only in response to further movements of the needle and take up mechanisms and completely independently of hook rotation. The raising of the needle eye together with application of tension to the needle thread by operation of the needle thread take up 58 will cause the limb Ns of needle thread which is in the recess 250 beneath the bobbin case to exert a slight upward force on the bobbin case. Moreover, the upward lead of the thread limb Ns to the raised needle eye will carry the thread across the bevel 241 of the bobbin case as well as across the inclination of the slabbed portion 245 of the bobbin case. The combined effect of the upward force applied to the bobbin case together with the camming action of the bobbin case surfaces 241 and 245 will cause the needle thread limb Ns to pass between the bottom surface 221 of the bobbin case and the annular land 210 of the rotary hook boss 206, as indicated by the alternate position marked NsI in FIG. 10A. The needle thread loop is thus freed to pass upwardly about the frusto-conical outer surface of the bobbin case sidewall 222 and upwardly out of the shelf 260 thereon to be drawn over the upper flange 230 of the bobbin 41 between the bobbin and the leaf spring 42 and thence through the needle aperture 30 and into the work fabric. The direction in which the needle thread loop is drawn from the stored position on the bobbin case is upwardly away from the rotary hook beaks and the manipulation of the needle thread loop thus occurs completely about the bobbin 41 within the bobbin case so that a lockstitch thread concatenation is obtained. It will be appreciated that as the needle thread loop is drawn upwardly from stored position on the bobbin case, the needle thread loop will be detained momentarily first by the bowed extremity 216 of the spring 215, then by the leaf spring 42, and finally by the rotation restraining shoulders 218, 243 on the cover plate 25 and bobbin case 40, respectively. The needle thread loop is thus controlled during the entire take up action while the stitch is being set so that the needle thread loop is prevented from accidentally assuming a position in the path of any of the hook beaks 205.

While the above described needle and loop taker thus cooperate in the formation of stitches in the absence of any predetermined timed relation therebetween, and the ratio of the rates of stitch forming motion of needle and loop taker may be varied during operation, it may be necessary to limit the maximum Speed ratio of needle to loop taker motion in order that perfect stitching may be attained with certainty.

One such limit of the maximum speed ratio is imposed by the necessity for at least one beak 205 to traverse the path of needle reciprocation within each interval during which the needle occupies the range of positions described above in which needle loop seizure is possible, If, for example, each interval of possible needle loop seizure corresponds to 30 of rotation of the needle drive shaft 50, and only one beak 205 is used, the maximum ratio of needle reciprocation to rotary hook rotation of 1 to 12 ought not to be exceeded if needle loop seizure is to be attained with certainty. The use of a plurality of hook beaks permits the maximum speed ratio to be increased. For instance, in the above example if four hook beaks 205 are employed this ratio limit becomes 1 to 3, and with six such beaks 205 the ratio limit becomes 1 to 2 which is most common in conventional lockstitch forming mechamsms.

While from the standpoint of needle loop seizure there is no theoretical limit to the number of hook beaks which may be used and, therefore, from the loop seizure standpoint no theoretical limit as to the maximum speed ratio, it will also be appreciated that an ascertainable increment of turning movement of the loop taker is required in order to position the seized needle thread loop in stored relation on the bobbin case. Since the stored needle thread loop must thereafter be drawn from the bobbin case by the needle and take up mechanisms before the succeeding stitch concatenation can take place, during which an additional increment of turning movement of the loop taker will occur, these considerations of thread manipulations will impose a practical limit to the maximum speed ratio attainable regardless of the number of beaks employed.

Although the rotary hook is preferably rotated at a constant speed, it will be appreciated that the rotary hook speed may be made variable, provided only that the maximum ratio of speed limits above described are not exceeded. It is an important facet of this invention that should variation of both loop taker and needle reciprocation rates be provided for, synchronism or predetermined correlation as between these rates need not be observed.

It will be understood that the loop taker 20 comprises only three relatively simple basic parts; the

hook body

201, 202 and 203 is simply a cup-shaped member with a planar bearing face which may be readily turned, cast, or mounded; the bobbin case 40 which also lends itself readily to manufacture by a moulding; and the top cover plate 25 which is simply an apertured sheet metal element. Since the bobbin case flange 226 simply rests upon the face of the rotary hook 20 and is not journalled in a raceway into which the thread can become lodged, jamming of the hook, which has been a particularly irking problem with certain known loop takers, is impossible with the present hook construction. The raised boss 206 within the cup-shaped rotary hook is necessary only when the hook is to be driven in untimed relation with the needle. If a precise timed relation is established, as is conventional, so that storage of the thread loop on the bobbin case becomes unnecessary the boss 206 may be dispensed with.

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

1. A loop taker for lockstitch sewing machines having an endwise reciprocatory thread carrying needle, said loop taker including an annular member, at least one radially extending needle loop seizing beak formed on said annular member, means supporting said loop taker for turning movement in said sewing machine about a central axis, said annular member formed on one face with a planar bearing surface perpendicular to said central axis, a bobbin case formed with a bearing flange engaging said planar bearing surface on said annular member, bobbin case retaining means supported independently of said loop taker on said sewing machine, andsaid bobbin case retaining means formed with bobbin case abutting surfaces providing the sole constraint for said bobbin case radially, axially and angularly relatively to said planar bearing surface on said loop taker.

2. A loop taker as set forth in claim 1 in which said bobbin case retaining means constrains said bobbin case bearing flange in engagement with only a portion of said annular bearing surface on said annular member.

3. A loop taker as set forth in claim 1 in which said loop seizing beak is defined on the annular member by a notch formed radially of said annular member and said needle loop seizing beak extends substantially to the plane of said planar bearing surface on said annular member.

References Cited UNITED STATES PATENTS 1,996,290 4/ 1935 Gunther 112-228 X 2,544,227 3/1951 Hohmann 112-184 2,966,130 12/1960 Johnson 112-184 FOREIGN PATENTS 537,634 2/ 1957 Canada.

HERBERT F. ROSS, Primary Examiner.