US3343510A

US3343510A - High speed rotary hook

Info

Publication number: US3343510A
Application number: US407483A
Authority: US
Inventors: John G Attwood; Bernard F Bishop
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1964-10-29
Filing date: 1964-10-29
Publication date: 1967-09-26
Anticipated expiration: 1984-09-26

Description

Sept- 26, 1967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED ROTARY HOOK Filed Oct. 29, 1964 3 Sheets-Sheet 1 Sept' 26, l967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED `ROTARY HOOK 5 Sheets-Sheet 2 Filed Oct. 29, 1964 Sept. 26, 1967 J. G. ATTwooD ETAL 3,343,510

HIGH SPEED ROTARY HOOK 3 Sheets-Shea?I 5 Filed Oct.. 29, 1964 'III V N sUnited States hatent 3,343,510 HiGH SPEED ROTARY HOOK .lohn G. Attwood, Oak Park, and Bernard F. Bishop, Chicago, iii., assignors to Union Special Machine Company, Chicago, lll., a corporation of Illinois Filed Oct. 29, 1964, Ser. No. 407,483 14 Claims. (Cl. 112- 228) ABSTRACT '0F THE DISCLOSURE A rotary hook, for use in a lockstitch sewing machine, which includes a rotary component secured to a drive shaft of the machine and a bobbin case holder disposed within the rotary component, rotation of said bobbin case with the rotary component being prevented 'by a stationary retaining finger carried by the frame of the machine and adapted to cooperate with the holder to prevent its rotation. An important feature of the construction is the provision of a race'way in the rotary component that is adapted to receive a radially extending rib on the bobbin case holder, said raceway being disposed eccentrically in rela-tion to thc axis of rotation of the rotary component. The eccentricity of the raceway is such that the point thereon which is disposed at the greatest distance from the axis of rotation -to the rotary component is so located that forces created upon high speed rotation of the rotary component are of such a character as to impart a minimum orbital movement to the bobbin case holder within the rotary component. Toward the foregoing end, the region of the raceway which is at a maximum distance from the axis of rotation of the rotary component is located at an angle of between 20 and 70 forwardly of a radial line extending from the end of the loop seizing beak of the rotary component to the axis of rotation of the latter. The foregoing feature enables the rotary component of the hook to be operated at especially high speeds, at least 14,000 rpm., without causing overheating or producing other objectionable results. Toward the same end the invention also provides special features for lightening the weight of the rotary component and the bobbin case holder. This is, in part, achieved by the provision of special grooves at spaced intervals around the circumference of the rib provided on the bobbin case holder. The construction in general is such that a shoulder on the bobbin case, which cooperates with a retaining finger, is urged against the latter with only a relatively small force at any time, thus enabling the free passage of the branch of a loop of thread between said shoulder and the retaining linger at the dcsircd time. This result is further insured by the formation of the retaining finger in such a way that the part thereof which cooperates with the shoulder on the bobbin case holder will yield readily as thread is drawn outwardly between the shoulder and retaining finger.

This invention relates to high speed lockstitch machines of the character employed in factories requiring the production of locltstitch seams in garments of a variety of dierent types. Heretofore there has been a definite limit upon the speed of operation of machines intended for the production of such seams, due to the necessity of rotating the hook at twice the speed of production of the stitches. Thus machines adapted to produce such stitches at the rate of 5000 per minute have required rotation of the hook at a rate of 10,000 per minute. This has led to considerable difficulty, in view of the excessive temperature and wear of various parts resulting from efforts to attain a higher speed of operation.

In accordance with the present invention the hook assembly is so constructed that the hook is capable of asfissia rice rotating ut 14,000 or more revolutions per minute, with the production of at least 7000 locksttchcs per minute. Toward this cnd va number of important features are incorporatcd in thc construction of and the control over the operation of the hook. ln the operation of a rotary hook it has been found desirable, at a certain point in its operation, to provide a clearance for the passage of the needle thread between a surface on the thread supplying container within the rotating component of the hook and a stationary linger or shoulder which prevents rotation of said container or basket, so as to permit withdrawal of the loop of needle thread that is carried around said basket, without danger of severing said thread. ln vertical yaxis hook machines a finger or similar member has frequently been provided to engage the basket to shift it slightly against the action of the frictional forces tending to rotate it along with the rotary component of the hook. But it has Ibeen found impracticable to provide such hooi; opening means in connection with horizontal axis hooks. In the patent to Attwood No. 2,941,488 it has been disclosed how to achieve the purposes of such a hook opening finger by the provision of a certain ccccntricity bctween the raceway of the rotary component of the hook, which cooperates with the rib on `the stationary' basket component, and the axis about which said rotary component is rotated. While this has proved to be highly beneficial, it has not achieved the high speed operation of the hook made possible by the prescrit invention.

This invention involves a combination of features which jointly contribute toward the desired end. ln the preferred embodiment of the invention there are three important features which contribute toward the achievement of the YStated result. One of these is the provision of eccentricity between the axis of the shaft which carries the rotary component of the hook and the raceway of said rotary component in a new relationship that serves to retain the thread basket or bobbin case holder in a relatively centralized position within the rotating component. For this purpose it has been found desirable to provide the major axis of such ecccntricity along a line that extends substantially in the opposite direction from thc axis of the shaft carrying the rotary component than that employed in the construction of the Attwood patent above mentioned. This construction is such that it does not pro vide automatic shifting of the bobbin case basket in a direction to offset the frictional forces that tend to turn the basket in the direction of rotation of the rotary component of the hook, as is done in the construction disclosed in said Attwood patent. Instead it serves, in combination with thc other features to he mentioned, to retain the basket in a substantially centralized position, i.e. with a minimum orbital movement having a .radius of not more than about .006 of an inch and preferably less, so as to minimize the force with which the rib on the basket is urged against the circumfcrentially extending and sun rounding surface of the raceway provided in the rotary component. The force of engagement of the cooperating opposed surfaces of the rib and raceway is reduced to about one-tenth of that encountered in hooks of the type heretofore proposed, including that disclosed in said Attwood patent. This greatly reduces the wear on and temperature rise of the cooperating surfaces and the necessity of lubrication thereof. lt also greatly reduces the impact or shock and noise incident to the high speed operation or hooks of previously suggested constructions.

A second feature of the invention, which contributes toward the foregoing end, is the provision of cut-away sections in the radially extending rib of the bobbin basket holder. The location of these cut-away portions of the rib has been carefully determined in accordance with the present invention, through the use of an oscilloscope presentation of the points in a cycle of rotation of the rotaryvcomponent of the hook at which the greatest amount of shock or impact, with resultant noise, is produced in the course of rotation of the rotary component. It was found, in accordance with these tests, that hooks of currently used constructions would, upon starting up, produce excessive impact and noise as the foremost end of the raceway, at the trailing side of the gap provided in the same in the region of the beak of the hook, reaches the leading end of the-rib on the bobbin case holder. However, the provision of a cut-away portion in the rib in a region about 36 forward in the direction of rotation of the point mentioned, coupled with the eccentricity of the raceway described above, was found to greatly reduce this noise and impact created upon the rotation of-the rotary component of the hook. Further oscilloscope studies indicate that noises created during the continued revolution of the new hook could be greatly reduced through the provision of additional cutaway portions in the bobbin case rib at further 36 circumferential intervals of the same. The total circumferential length of the rib is only about 288, in View of the necessity of omitting about a 72 angular portion thereof in the region in which the needle passes downwardly into the path of the loop seizing 'beak of the hook in order to permit free upward movement of the needle thread loop to complete formation of the stitch. The raceway in the rotary hook is also omitted to a similar but somewhat smaller extent. It is this gap in the circumferential areas of the rib and raceway, with resultant free shoulders that are brought into alignment upon each revolution of the rotary component, that apparently produces the excessive impact and noise, referred to above, in hooks of previously known constructions. On the other hand, the present invention serves to eliminate these noise and impact producing tendencies in the desired high speed operation of the machine, and thus enables the hook to be rotated at 14,000 r.p.m. without encountering the useful difficulties.

While in achieving the foregoing purposes of the cutaway portions of the rib their radial depth may -be varied to a certain extent, it has been found highly desirable to make them of the full radial extent of the ri'b on the bobbin case holder. Also it has been found desirable to make said cut away portions with a substantial circumferential extent, about or more, and also to provide them with smooth inwardly sloping surfaces forming a substantially V-shaped configuration. These aspects of the invention serve to reduce the weight of the bobbin case holder and also to overcome the danger of having the needle thread caught in the grooves formed by the cut away .portions ofthe rib. The reduction in the weight of the holder contributes toward minimizing the force with which the circumferentially extending opposed surfaces of the rib and raceway are urged together upon any lateral shifting of the bobbin case holder as a result of operation of the hook, and reduces the lubrication requirements for these surfaces.

The location of the maximum eccentricity of the raceway, in accordance with the present invention, is such that it does not produce the opening action to permit free passage of the needle thread between the bobbin case holder retaining nger and the cooperating shoulde-r on said holder. But the overall construction is such that the force with which said shoulder is urged against said finger is relatively small, as compared with hook structures now in use, such as that disclosed in the` above mentioned Attwood patent. In the latter construction, the

.average value of the indicated force has been found to be `between about 2 and 4 ounces, depending upon the speed of operation of the machine, i.e. between 3000 and 600,0 rpm., and it goes as high as ounces in the course of a cycle of rotation of the hook, when the machine is operated at 6000 r.p.m. These figures contrast sharply with the average force or pressure of about 0.2 ounce and maximum or peak pressu-re of 0.5 ounce created during the operation of the vhook of this invention. Moreover, the average and peak pressures developed by the latter remain substantially uniform as the speed of operation of the machine is increased from 3000 to 7000 or more -r.p.m.

A third feature of the overall combination of the present invention is the provision of a retainer for the bobbin case holder which is a thin at spring carried by the retainer for cooperation with the shoulder on the bobbin case holder to prevent rotation of the latter with the rotary component of the hook. This spring element is interposed between said shoulder and a more rigid finger that enters the recess in the outer face of the bobbin case holder and it provides the means cooperating with theshoulder men tioncd. This enables the needle thread loop to be drawn upwardly between the spring element and the specified shoulder, even though the cooperating surfaces remain engaged under a relatively small force at the time the thread loop-is so drawn upwardly. The spring clement tiexes sufficiently readily -to permit this to be done with out danger of breaking the thread, when the greatly reduced force discussed above is brought about by the other features of the invention. If desired, a thin piece of plastic or synthetic rubber may be provided between the spring element mentioned and the more rigid finger. This plastic or synthetic rubber strip acts as a shock absorber and keeps the thin spring element from vibrating.

Wtih the foregoing features of the yinvention in mind, a preferred embodiment of the overall construction will now be described in detail -by reference to the accompanying drawings in which:

FIG. 1 is an enlarged face view ofthe improved rotary hook construction, shown in relation to the path of the needle and illustrating the positions of the needle thread and bobbin thread at a point in the cycle of operation of the machine at which the needle thread loop is about to be carried upwardly and released from the hook structure;

FIG. 2 is an enlarged perspective view of the improved rotary hook, showing the rotary component and the cooperating threads at a slightly later point in the cycle of operation ofthe machine; i

FIG. 3 is a similarly enlarged plan view of the hook structure and of the bobbin case holder retainer;

FIG. 4 is a detail plan view, on a slightly larger scale,

' of a portion of the bobbin case holder retainer member illustrated in FIG. 3;

FIG. 5 is an enlarged end view of the retainer member as seen from the left in FIG. 4;

FIG. 6 is a view similar to FIG. 4 showing, on an enlarged scale, a modified finger construction on the retainer, incorporating the above mentioned thin piece of plastic or synthetic rubber between the thin spring member and the more rigid part of the retaining finger;

FIG. 7 is a rear view of the bobbin case holder, on a quiteenlarged scale, and shows the preferred form and angular disposition of the cut-away regions ot' the radially extending rib;

FIG. 8 is a face View of the rotary component of the hook, on a scale comparable with the showing of the bobbin case holder in FIG. 7, and shows the disposition of the eccentricity of the raceway in the hook in relation to the axis of the shaft which carries the rotary component;

FIG. 9 is an enlarged face view of the bobbin case holder;

FIG. 10 is a similarly enlarged plan view of the bobbin case holder; and

FIG. 11 is an enlarged side elevational view of said holder.

The preferred embodiment of the invention as disclosed herein is particularly suited for use in connection with a lockstitch sewing machine of the type disclosed in the 'patent to Covert No. 2,977,910, granted Apr. 4, 1961.

main drive shaft of the machine. Within the rotary component of the hook there is mounted a bobbin case holder 12 adapted to retain a bobbin case 13 of conventional form. As shown in FIG. 3 there is provided a retainer member 14 for preventing rotation of the bobbin case holder along with the rotary component of the hook as a result of frictional drive forces created between these elements. Member 14 is secured to the under face of the work supporting member of the base portion of the frame of the machine by means of bolts or screws 15. Toward its left end the element 14 (FIG. 3) is provided with an inwardly and upwardly extending finger 16 arranged to cooperate with a groove 17 in the upper portion of the face of lthe bobbin case holder. Adjacent the finger 16 there is provided a similarly shaped thin spring nger 16a also cooperating with the groove 17. This arrangement is such that in the rotation of the rotary component of the hook, in a counterclockwise direction (FIG. l), the shoulder of the groove 17 to the right of the spring finger 16a is urged under a light pressure or force against the spring finger 16a.

As shown in FIG. 3, the bobbin case holder is provided with an opening 1S through which the needle is reciprocated in the course of operation of the machine. This enables carrying the needle downwardly into the bobbin case holder beneath the loop seizing beak of the rotary component of the hook. It will -be understood that as the needle rises it tends to throw out a slight loop in the path of the beak. The bobbin case holder has a forwardly and upwardly extending outer flange portion 19 (FIGS. 9 and l0), this having in its upper region the groove 17 described above. The bobbin :case holder has a main body portion 20 of substantially cylindrical form, adapted to tit into a cavity Within the rotary component of the hook. Various parts of the bobbin case holder are cut-away to lighten the overall weight of the holder. Thus the base or inner end of the holder is formed by a diametrically extending part 21 with cut-away portions at each side thereof. At the center of part 21 there is suitably secured an outwardly extending pin or stud 22 arranged to receive the central tubular portion of the bobbin case 13. Toward the outer end of the stud 22 there is provided a groove 22b, leaving the head portion 22a of substantially the same diameter as the main body of the stud. This provides for locking the bobbin case within the holder by the conventional operation of a lever 13a and a slide element 13b carried by the `bobbin case, said slide element cooperating with a cut-out portion 19a in the flange of the bobbin case holder to retain the bobbin case against rotation within the holder.

Extending around the body portion 20 of the bobbin case holder is a rib 23 adapted to cooperate with the raceway in the rotary component, indicated at 24 in FIG. 8. The rib 23, as shown in FIG. 7 is cut-away over an arc of about 72 in its upper portion to enable the passage of the loop of needle thread as this is drawn upwardly after having been carried around the bobbin case holder. At intervals of preferably about 36 from the edge 23a of the rib there is provided a series of grooves 23h having their outer ends extending over an arc of approximately and having a generally V-shaped configuration with smoothly rounded surfaces at their radially inner ends. While the grooves or cut-away portions 23h of the rib need not extend the full radial depth of the rib, they preferably do so. Also the surface 23b (FIG. 10) of each groove is inclined at an angle of between and 30 to a radial line extending from the axis of the stud 22 to the outer edge of the adjacent segment of the rib. The opposite surface 23h" of each groove is preferably inclined at an angle of about 45 in the opposite direction. This disposition of the two surfaces avoids any danger of having the thread loop caught in the grooves, along with other advantages. Since FIG. 7 is a rear view of the bobbin case holder it will be appreciated that the edge 23a is about in alinement with the right hand edge of part 21 as Viewed in FIGS. 9 and 10. The other edge 23e` (FIG. 7) of the 72 gap in the rib is to the left of part 21 in FIG. 9. As has been explained above, the spacing of the cut-away portions 23b has been determined through oscilloscope studies, and they have been found to greatly reduce the impact and noise incident to the rotation of the rotary component of the hook. Also they serve to lighten the weight of the bobbin case holder and to provide a smaller area of contact between the rib and the cooperating raceway of the rotary component. Moreover the particular location ofthe center of eccentricity of the raceway of the rotary component of the hook, coupled with the other features described, is such as to impart a minimum path of orbital movement to the bobbin case holder during the rotation of the rotary component of the hook.

Turning now to the construction of the rotary component of the hook, this is similar to conventional constructions heretofore employed with the exception of a particular disposition of the eccentricity of its raceway in relation to the hook beak. As best shown in FIGS. 1 and 2 the rotary component has a loop seizing beak 26 which is carried counterclockwise upon rotation of the hook. The outer peripheral portion of the rotary component involves two segments 27 and 2S which are secured by screws to the main body of the rotary component. The separate construction of these elements enables the assembly of the bobbin case holder within the raceway of the rotary component, which is in part provided by the element 27. Referring to FIG. 8, there is indicated the disposition of the eccentricity of the raceway in relation to the axis of the hook shaft 11. This axis is indicated at 11a and the center of the raceway is indicated at 25a. It will be seen that the latter is disposed along a line 25 extending radially from the axis 11a of the hook shaft and is disposed preferably at a distance of .0010 inch, to provide that amount of eccentrieity between these axes in the particular direction indicated. Line 2S is preferably disposed at an angle of about 45 forwardly of the end of the hook beak 26, in the direction of rotation of the latter, but such angle may be between 20 and 70.

Returning now to FIGS. l and 2, the element 28 of the rotary component is provided with a forwardly extending spur 28a spaced radially outwardly to a slight extent from the hook beak and forming a V-shaped recess for the retention of the needle thread which is seized by the beak. Segment 27 of the rotary component has a thread guiding projection 27a forwardly of the beak 26 and spur 28a. This insures proper control over the needle thread loop as the latter is released from the beak and is pulled upwardly in the tightening of the stitch that has been formed. It will be appreciated that as the needle 29 is reciprocated through an opening in the work supporting surface 30, and carried into the path of the hook beak 26, the latter is enabled to pick up the loop of the needle thread 31 and carry this around thread 32 supplied from the bobbin within the bobbin case. The latter thread is passed outwardly from the interior of the bobbin case to a spring retaining linger 33 and then upwardly through an eyelet 33a to its point of incorporation in the work being stitched.

As the seized loop of the needle thread is carried around the hook by the beak 26, the branch thereof extending from the work piece being stitched, on support 30, is urged outwardly by the edge 23e of member 2S of the rotary component so as to pass along the outer surface of the bobbin case and its holder. In FIG. l the loop is shown in the position assumed after about a half revolution of the rotary component in which the beak has seized the thread. In FIG. 2 the needle thread loop is shown in the position assumed after about another revolution ofthe rotary component, at which time the loop is pulled away from the beak 26 by the action of the usual take-up mechanism provided on the machine, and it is temporarily retained by the projection 27a of segment 27 of the rotary component. As the hook continues to rotate, the loop will be release from the projection 27a and the take-up mechanism will draw the loop upwardly against the underside of the work. In doing this the branch of the loop referred to above will be pulled upwardly between the spring finger 16a on the retainer 14 and the cooperating shoulder of recess 17 in the bobbin case holder. This can be readily done in view of the relatively light pressure with which said shoulder on the bobbin case holder is urged against the spring linger 16a, and it is further facilitated by the ability of the latter to flex away from said shoulder.

As has been previously indicated, it has been found desirable to insert a thin strip of rubber or yieldable plastic material between the rigid finger 16 and the spring finger 16a of the retainer 14. This is indicated at 34 in FIG. 6. The provision of such yieldable material serves to eliminate or minimize any vibrations that may be imparted to the spring finger 16a as the thread loop is drawn upwardly between it and the shoulder on the bobbin case holder, and is then released from the slight gripping force of the spring finger. Layer 34 will yield suflciently to permit the slight flexing of spring finger 16a, but the latter will be prevented from vibrating upon the release of the thread. Some vibration may also be imparted to the spring finger 16a, in the absence of the layer 34, due to the unavoidable impact action created upon starting up of the machine. Such impact action appears to be due to the fact that a certain amount of clearance must be provided between the rib and raceway of the hook assembly to reduce the frictional drag of the rotary component and the bobbin case holder and to provide space for a thin lubricant nlm. This clearance naturally causes the bobbin case holder to settle by gravity, when the machine is at rest so that the holder is slightly off center in relation to the raceway. The present invention serves to bring the bobbin case holder rather quickly into a substantially centralized position as the machine is started up, and serves to reduce the orbital path of movement of the holder to a minimum during operation of the machine.

The combination of the several features of the present invention, including the extent and direction of eccentricity of the hook raceway in relation to the axis of the hook shaft 11, the lightening of the overall weight of the bobbin case holder, the provision of periodic grooves or cutaway regions in the rib 23 of the bobbin case holder around its circumferential extent, the provision of the yielding finger 16a on the retainer 14, and also the provision of the rubber or plastic insert 34 between the iingers 16 and 16a of the retainer, all contribute toward increasing the permissible speed of operation of the machine, beyond anything previously attained, without producing objectionable impact and noise and with the production of uniform stitches. A hook constructed in accordance with the invention has been trial tested and found capable of operation at exceptionally high speed for long continuous periods of time, without developing objectionable impact and noise, without overheating of the hook, and with a minimum requirement of the lubrication of the cooperating surfaces of the rib and raceway of the hook assembly. In fact it was operated continuously at 14,000 r.p.m. for 14 hours, and during the last three hours of this test the supply of lubricant to the raceway was cut off. Throughout the test, no objectionable impact and noise was developed and no overheating of the hook was created. Those conducting the test found the hook to be the smoothest acting hook they had ever tested, even with its higher than usual speed of operation. This is indicative of the low torque transmitted to the bobbin case holder and the low lubricant requirement of the improved construction.

While the particular construction shown and described herein has been found exceptionally well suited to achieve the highly advantageous results explained above, various departures from the precise form shown may be made and still obtain at least some of the important advantages of the invention. Thus, as indicated by the foregoing, certain definite advantages result from the particular point or line of maximum eccentricity of the raceway. While this should preferably be located along the line 25 indicate-d in FIG. 8, it may deviate somewhat from that line to the extent of as much `as 25 in either direction. As for the grooves or cut-away portions provided in the rib 23 of the bobbin case holder, those are most desirably of the form and in the location described, but both of these factors may be varied to some extent. They may, for example, be spaced at a somewhat different angular distance apart and either or both their circumferential extent at their outermost regions and their radial depth may be varied to some extent, Their radical depth, for example, need not be to the full radial dimension of the rib. However the full depth shown in the drawings contributes toward the advantage of reducing the weight of the holder. Furthermore a relatively large length of the grooves in a circumferential direction serves to reduce the area of the surface of the rib cooperating with the circumferentially extending surface of the raceway, thereby reducing the torque or frictional force created upon the rotation of the rotary component. This objective is also achieved to a certain extent by the chamfered or beveled edges shown on the outer circumferential surfaces of the projecting portions ofthe rib.

Important aspects of the invention are the maintenance of a substantially uniform and low pressure of the shoulder on the bobbin basket against the retaining finger, the provision of a resilient and readily yieldable portion of the finger that cooperates with said shoulder, and the generation of a minimum amount of heat from the frictional cooperation of the rib with the raceway. The construction shown serves to hold the temperature of the hook at a level comfortable to the hand.

What is claimed is:

1. In a lockstitch sewing machine having a driven shaft, a rotary hook having a rotary component secured to said shaft, said rotary component having a loop seizing beak, a bobbin case holder within said rotary component, a stationany retaining finger cooperating with said holder to prevent rotation thereof with said rotary component, said rotary component having a substantially annular raceway therein and said bobbin 4case holder having a radially extending rib cooperating with said raceway, said raceway being disposed slightly eccentrically in relation to the axis about which said rotary component is rotated, the region of said raceway which is at a maximum distance from the axis of rotation of said rotary component being located within a one-quarter circumferential arc extending forwardly of the hook beak and being so disposed as to maintain said bobbin case holder with minimum orbital move-ment within said rotary component.

2. In a lockstitch sewing machine as set forth in sclaim 1, a line extending from the axis of rotation of said rotary component of the hook to said region of the raceway which is at a maximum distance from said axis of rotation extending at an angle of between 20 and 70 forwardly of a radial line extending from the end of said beak to the axis of rotation of said rotary component.

3. In a lockstitch sewing machine as set forth in claim 2, a thread carrying needle reciprocable along a path substantially perpendicular to the axis of rotation of said rotary component of the hook, said raceway being omitted in the region of said hook beak over an arc of at least 45 and said rib of said bobbin case holder being omitted over an arc of at least 60 in the region of the reciprocation of said needle, said rib on said bobbin case holder being grooved in successive areas disposed at substantially equal distances apart around the circumference of said rib from one end thereof to the opposite end thereof, said grooved areas of said rib being provided with gently lsloping surfaces from the outer face of the rib toward the radially inward portions of said grooved areas and there being merged smoothly into each other to provide a substantially V-shaped configuration.

4. In a lockstitch sewing machine as set forth in claim 3, the radial center lines f said grooves being disposed at about 36 intervals around the circumference of said rib.

5. In a lockstitch sewing machine as set forth in claim 4, said grooved areas of said rib extending over an arc of about around the periphery of said rib.

6. In a lockstitch sewing machine as set forth in claim 1, said retaining finger having a portion thereof cooperating with a shoulder on said bobbin case holder, said portion of said finger being so formed and retained as to enable the same to yield slightly upon the application of a relatively small lateral force thereto.

7. In a lockstitch sewing machine as set forth in claim 3, said retaining finger having a portion thereof cooperating with a shoulder on said bobbin case holder, said portion of said finger being so formed and retained as to enable the same to yield slightly upon the application of a relatively small lateral force thereto.

8. In a lockstitch sewing machine as set forth in claim 1, said bobbin case holder having a groove in the outer face thereof, said retaining finger having a relatively rigid portion and a yieldable spring portion spaced slightly from said rigid portion both extending into said groove, said yieldable spring portion cooperating with a shoulder at one side of said groove and being adapted to yield readily upon the passage of thread from said needle between said shoulder and said spring portion.

9. In a lockstitch sewing machine as set forth in claim 8, a rubber like material filling the space between said rigid portion and said yieldable spring portion of said finger.

10. In a lockstitch sewing machine as set forth in `claim 1, said bobbin case holder having a shoulder that is urged against said retaining finger upon operation of the hook, the extent and direction in which the axis of said raceway is disposed away from the axis of rotation of said rotary component being such as to create substantially the same low pressure of the shoulder on the bobbin case holder against the retaining finger during all speeds of operation of the machine above 3,000 r.p.m.

11. In a lockstitch sewing machine as set forth in claim 10, the rib on said bobbin case holder being provided with grooves in the circumferential face thereof at spaced intervals, such grooves substantially reducing the area of said circumferential face that cooperates with the circumferential wall of said raceway in the rotary component and thereby greatly reduces the torque applied to the bobbin case holder upon rotation of the rotary `component.

12. In a lockstitch sewing machine as set forth in claim 11, said area of the circumferential face of the rib being reduced to such an extent that the peak pressure of said shoulder against said finger is not more than about 0.5 ounce during each revolution of the rotary component and the average pressure is about 0.2 ounce.

13. In a lockstitch sewing machine as set forth in claim 1, the disposition and amount of the eccentricity of said raceway in relation to the axis of rotation of said rotary component being such yas to cause the orbital movement of said bobbin case holder during al1 operations of the machine to be substantially cincular and have a radius or not more than about .006 of an inch.

14. In a lockstitch sewing machine as set forth in claim 3, the surfaces at one side of each of said grooves provided in said rib which extend from the inner to the outer ends thereof being inclined at an angle between 20 and 30 to a line extending from the axis of rotation of said rotary component to the outer ends of said surfaces, said inclination being in the direction of approach of the loop seizing beak of said rotary component, and the surfaces of said grooves lat the opposite sides thereof being inclined at a greater angle in the opposite direction.

References Cited UNITED STATES PATENTS 1,364,279 1/ 1921 Hohmann 112-228 2,108,412 2/1938 Sauer 112-228 2,232,624 2/1941 Nissen 112-181 X 2,352,598 7/1944 Billington 112-181 X 2,941,488 6/1960 Attwood 112-228 3,074,367 1/ 1963 Habedank et al 112-228 JORDAN FRANKLIN, Primary Examiner.

H. ROSS, Examiner.

Claims

1. IN A LOCKSTITCH SEWING MACHINE HAVING A DRIVEN SHAFT, A ROTARY HOOK HAVING A ROTARY COMPONENT SECURED TO SAID SHAFT, SAID ROTARY COMPONENT HAVING A LOOP SEIZING BEAK, A BOBBIN CASE HOLDER WITHIN SAID ROTARY COMPONENT, A STATIONARY RETAINIG FINGER COOPERATING WITH SAID HOLDER TO PREVENT ROTATION THEREOF WITH SAID ROTARY COMPONENT, SAID ROTARY COMPONENT HAVING A SUBSTANTIALLY ANNULAR RACEWAY THEREIN AND SAID BOBBIN CASE HOLDER HAVING A RADIALLY EXTENDING RIB COOPERATING WITH SAID RACEWAY, SAID RACEWAY BEING DISPOSED SLIGHTLY ECCENTRICALLY IN RELATION TO THE AXIS ABOUT WHICH SAID ROTARY COMPONENT IS ROTATED, THE REGION OF SAID RACEWAY WHICH IS AT A MAXIMUM DISTANCE FROM THE AXIS OF ROTATION OF SAID ROTARY COMPONENT BEING LOCATED WITHIN A ONE-QUARTER CIRCUMFERENTIAL ARC EXTENDING FORWARDLY OF THE HOOK BEAK AND BEING SO DISPOSED AS TO MAINTAIN SAID BOBBIN CASE HOLDER WITH MINIMUM ORBITAL MOVEMENT WITHIN SAID ROTARY COMPONENT.