US3747547A

US3747547A - Bobbin changing mechanism method and product

Info

Publication number: US3747547A
Application number: US00118148A
Authority: US
Inventors: N Mayer; S Lanes
Original assignee: BOBBIN MONITOR CORP
Current assignee: BOBBIN MONITOR CORP
Priority date: 1971-02-23
Filing date: 1971-02-23
Publication date: 1973-07-24
Anticipated expiration: 1990-07-24
Also published as: IT947830B; FR2127695A5; DE2208557A1

Abstract

Coreless bobbins are loaded from a supply into an empty bobbin case and then automatically transferred into the bobbin holder and hook assembly of a conventional lockstitch sewing machine. Upon runout of the bobbin thread, and upon the signalling of such runout electrically, the empty bobbin case is automatically withdrawn from the holder and hook assembly for reloading and a new loaded bobbin case is automatically inserted into the holder and hook assembly of the sewing machine.

Description

United States Patent [1 1 Mayer et al.

[ July 24, 1973 BOBBIN CHANGING MECHANISM METHOD AND PRODUCT [75] Inventors: Nathan Mayer, East Brunswick;

Stanley S. Lanes, Matawan, both of NJ.

[73] Assignee: Bobbin Monitor Corporation,

Jamesburg, NJ.

[22] Filed: Feb. 23, 1971 [21] Appl. N0.: 118,148

[52] 11.8. CI. 112/186 [51] Int. Cl D05b 59/04 [58] Field of Search 112/186, 185, 180,

[56] References Cited UNITED STATES PATENTS Schumann et al. Dobner et al 2/1956 Schuman et al. 112/180 2,507,470 5/1950 Hirsch 112/181 2,808,795 10/1957 Wortham 112/186 X 3,376,838 4/1968 Schiffmacher et al 112/186 FOREIGN PATENTS OR APPLICATIONS 908,215 10/1962 Great Britain 112/186 Primary Examiner-H. Hampton Hunter Attorney-'-Amster & Rothstein [57] ABSTRACT Coreless bobbins are loaded from a supply into an empty bobbin case and then automatically transferred into the bobbin holder and hook assembly of a conventional lockstitch sewing machine. Upon runout of the bobbin thread, and upon the signalling of such runout electrically, the empty bobbin case is automatically withdrawn from the holder and hook assembly for reloading and a new loaded bobbin case is automatically inserted into the holder and hook assembly of the sewing machine.

15 Claims, 20 Drawing; Figures PAIENIEUJUL 24 ma 747, 547

SHEET I 1 [1F 5 BOBBIN CHANGING MECHANISM METHOD AND PRUINUCT The present invention relates generally to methods and apparatus for the automatic changeover of bobbins in sewing mechanisms, and in particular to an improved method for feeding bobbins to a sewing machine, an automatic bobbin changing apparatus and improved components and product utilizable with such method and apparatus.

In the typical lockstitch sewing machine utilizing a bobbin thread wound upon a bobbin spool, the bobbin changing procedure involves the machine operator in a number of sequential steps which usually include reaching under the machine and removing the bobbin case containing the exhausted or partially exhausted spool of bobbin thread, unlatching the spool from the case, removing the spool and replacing the same with a new spool containing a full bobbin, reloading the bobbin case into the holder and hook assembly of the machine and thereafter re-establishing the stitch by the hand manipulation of the sewing machine causing the needle thread to engage the bobbin thread through the throat plate.

Particularly with the advent of present day sewing machines which are capable of operating at stitching rates in the range of 5,000 to 6,000 stitches per minute, the manual bobbin change sequence presents a number of practical problems to the machine operator. Initially, in the absence of an automatic changing mechanism, or at the very least of a bobbin runout signalling system, the operator must be concerned with when the supply of bobbin thread will be exhausted. This often results in operator slowdown toward the end of the period in which the operator feels that the bobbin thread is about to be exhausted. Frequently, an operator will discard partially exhausted bobbins and will reload the sewing machine prematurely or will completely exhaust the supply of bobbin thread, with the necessity of then pulling back the work and restitching. In many fabrics, pull-back and restitching causes the restitched length to have a patchy appearance; and indeed many fabrics cannot tolerate the extra needle holes formed incident tothe needle penetration without actual stitching due to the exhausted bobbin supply and the resulting product becomes a reject. Further, there is a potential for the provision of a double stitch line if the operator is not particularly careful in retracing his or her steps in the work. Still further, when utilizing a conventional bobbin containing bobbin thread wound on a reusable metal or throwaway type of spool, there is a tendency for the bobbin spool to turn within the bobbin case which may result in tangling or fouling of the bobbin thread. This occurs most frequently when an operator has repetitive short runs (i.e. pockets) and is caused by the inertia of the bobbin in the bobbin case. In all events, the bobbin change time is totally unproductive, usually representing anywhere from 40 seconds to 60 seconds for the operator to go through the change se quence. Between the bobbin changing times, including the inherent operator slowdown when the operator believes that the bobbin thread is about to run out, the need for restitching and the potential for fouling of the bobbin thread, there can be a substantial loss in operator productivity, particularly, if in response to bobbin thread run-out or tangling of the bobbin thread, the needle thread, and possibly the needle as well, break.

Obviously, there exists a need for improved bobbin changing techniques and methods for the vast number of lockstitch sewing machines which are in widespread use throughout the world. Although a variety of approaches have been suggested to avoid the foregoing difficulties, to our knowledge there has been no system or method evolved which as by a simple attachment to a conventional sewing machine and the provision of an appropriate hand-operated or automated control, the machine operator is automatically advised of the imminent runout of the bobbin thread, with the warning occurring sufficiently in advance of runout to enable the operator to immediately stop sewing and by a simple manipulation, such as pushing a button or pressing a switch, is able to initiate a bobbin changing cycle during which the empty bobbin case in the sewing machine is automatically removed and replaced by a bobbin case loaded with bobbin thread. Thereupon, the operator, without further adieu and with minimum risk of bobbin thread fouling, loss of stitch or breaking of a needle or needle thread, is able to resume the stitching operation.

Broadly, it is an object of the present invention to provide improved mechanisms and techniques obviating one or more of the foregoing difficulties and achieving one or more of the foregoing objectives. Specifically, it is within the contemplation of the present invention to provide a bobbin changing mechanism and method and related bobbin assembly and construction which facilitates automatic bobbin reloading initiated prior to bobbin thread runout; which enables the stitching operation to be discontinued prior to improper stitching; which provides a rapid and automatic bobbin changing cycle and the reestablishment of the stitching operation; and which accomplishes the foregoing with minimum risk of machine malfunction, operator fatigue and lost productive time.

The bobbin changing method and apparatus of the present invention employs an improved bobbin assembly which comprises at least two toroidal coreless wound bobbins disposed in leading and trailing relation to each other and in axial alignment with each other. Preferably, each of the bobbins includesplural bobbin thread convolutions packed to provide a toroidal body having a substantially cylindrical outer peripheral wall adapted to conform to and fit snugly within the bobbin case and terminating at its opposite ends in leading and trailing faces. The leading and trailing bobbins are interconnected by an intermediate length of bobbin thread extending from the leading face of one of the bobbins at its inner periphery, over its outer peripheral wall, over the outer wall of the trailing one of the bobbins and then merging with the toroidal body thereof at its trailing face. Advantageously, this bobbin assembly can include a substantial number of individual bobbins disposed in axial alignment one behind the other for automatic feed to the sewing machine such that the supply need not be replenished more frequently than several (i.e. two or three) times a day as compared to a typical sewing machine running on straight goods which may require as many as seven to 10 changeover-s an hour. 1

In accordance with method aspects of the present invention, woundcoreless bobbins are fed in succession in the required bobbin case to the bobbin holder of a sewingmachine by forming a bobbin assembly of the foregoing type including at least two toroidal coreless and cheekless wound bobbins in leading and trailing relation to each other, loading the leading bobbin into the bobbin case by axially moving the leading bobbin away from the trailing bobbin and while still connected thereto by an intermediate length of bobbin thread and then moving the loaded bobbin case from the location at which it is loaded into a transfer location in axial alignment with the bobbin holder, with the leading bobbin still connected to the trailing bobbin to draw out said intermediate length of bobbin thread. Thereupon, the intermediate length of bobbin thread is severed at a point removed from the loaded bobbin case to leave a tail of bobbin thread on the leading bobbin. In the final step, the loaded bobbin case is moved into the bobbin holder with the bobbin thread tail extending therefrom. In response to the first needle stroke, the bobbin thread tail is pulled under the tensioning spring of the bobbin case and guided into stitch-forming relation with the needle thread, such that the sewing machine is capable of resuming its stitching function in its normal mode.

In accordance with apparatus aspects of the present invention, there is provided an automatic bobbin changing mechanism for a sewing machine of the type which utilizes a bobbin case containing a wound bobbin and received within a bobbin holder for engagement of the bobbin thread by a hook rotating on a hook axis which mechanism comprises a support adapted to be mounted on the sewing machine, for example, by replacing the conventional slide plate of the sewing machine. A carrier is mounted on the support for rotation about a carrier axis extending parallel to and offset from the hook axis, with the carrier including at least two bobbin case receivers at circumferentially spaced locations. Each receiver is adapted to receive a bobbin case for transfer between a bobbin loading position at a removed location from the bobbin holder and a case transfer position at a confronting location in alignment with the bobbin holder. Bobbin loading means are provided at the removed location which are adapted to receive a supply of coreless bobbins for feed one at a time into empty bobbin cases presented successively in the bobbin loading position. Provision is made for turning the carrier to bring the loaded bobbin case into thecase transfer position at which time means are operable to disengage the loaded bobbin case from its receiver and transfer the same to the bobbin holder of the sewing machine. Sensing means are operable to detect the runout of the bobbin thread in the loaded bobbin case in the sewing machine and means are operable in response to the sensing means to disengage the empty bobbin case from the bobbin case holder and return the same to the receiver at the case transfer position for movement to the bobbin loading position for the reloading of the empty bobbin case from the bobbin supply.

The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of a presently preferred but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a plan view with parts broken away showing a typical sewing machine including a bobbin feeding mechanism or attachment embodying features of the present invention;

FIG. 2 is a perspective and diagrammatic view showing the bobbin changing mechanism in elemental form to facilitate an understanding of the invention, with the mechanism shown in the running mode of the sewing machine prior to a bobbin changing cycle;

FIG. 3 is a fragmentary view similar to FIG. 2 but showing the bobbin changing mechanism in its case transfer phase, with the transfer member being positioned to pick up the empty bobbin case in the conventional bobbin case holder and hook assembly of the sewing machine; a

FIG. 4 is a fragmentary view similar to FIG. 3 but with the case transfer phase advanced to the point where the empty case has been withdrawn from the bobbin case holder and reloaded into the carrier of the bobbin changing mechanism;

FIG. 5 is a diagramatic view similar to FIG. 4 but with the carrier having rotated through to bring the empty case into the bobbin loading position, and with the transfer phase advanced to the point wherein a loaded bobbin case has been engaged within the holder and hook assembly of the sewing machine;

FIG. 6 is a simplified diagramatic and schematic showing of a bobbin thread runout detection system embodied in a simplified form of the present invention;

FIG. 7 is an elevational view, on an enlarged scale, of an improved bobbin case employed in the present mechanism, shown from the closed base wall end thereof;

FIG. 8 is a sectional view, partially taken along line 88 of FIG. 7 and showing in full and dotted lines the transfer head employed with the bobbin case during the transfer phase of the bobbin changing cycle which includes a first sequence during which an empty bobbin case is withdrawn from the bobbin holder and a second sequence, after a loaded bobbin case is brought into the case transfer position, during which the transfer head loads the bobbin case into the bobbin holder;

FIG. 9 is a bottom plan view of the improved bobbin case of the present invention taken on FIG. 8 and showing the bobbin case as held within the bobbin holder of a conventional sewing machine and with the bobbin thread emerging therefrom beneath the adjustable tension spring;

FIG. 10 is a diagramatic elevational view showing the stitching cycle stopped and at a point wherein the previous bobbin thread has run out and a new bobbin thread is in position beneath the sensing contact preparatory to reestablishment of stitching;

FIG. 11 is a view similar to FIG. 10 at a later time in the stitch forming sequence;

FIG. 12 is a view similar to FIG. 11 but at a still further time in the stitching-forming sequence in which a stitch is substantially formed after the start-up of the sewing machine following bobbin thread replenishment;

FIG. 13 is a diagramatic and sectional view along a typical stitch line illustrating the segment thereof which includes the overlapping portions of bobbin thread resulting from runout of one bobbin, replenishment of the bobbin thread and pickup of stitching;

FIG. 14 is a sectional view, on an enlarged scale, taken substantially along the line 14-14 of FIG. 1 and showing the details of a typical bobbin changing mechanism embodying features of the present invention as mounted on a lockstitch sewing machine in operative relation to the bobbin case holder and hook assembly thereof;

FIG. shows an illustrative cam development for the main actuating cam of the bobbin changing mechanism;

FIG. 16 is a diagramatic showing of the cam development, stretched out for convenience in illustration, and including progressive showings at various times in the bobbin changing cycle to assist in understanding the present invention;

FIG. 17 is a sectional view taken substantially along the line 17-17 of FIG. 14 and looking in the direction of the arrows showing the mechanism at a point in its cycle wherein a loaded bobbin case is waiting at the bobbin loading position removed from the case transfer position and during the normal stitching mode of the sewing machine between the reloading of bobbins;

FIG. 18 is a view similar to FIG. 17 but showing the loaded bobbin case as it approaches the case transfer position and with an empty bobbin case approaching the bobbin loading position, the carrier having rotated counterclockwise through something less than 180 from the position illustrated in FIG. 17;

FIG. 19 is a sectional view taken substantially along the line 19-19 of FIG. 14 and looking in the direction of the arrows; and,

FIG. 20 is a sectional view taken substantially along the line 20-20 of FIG. 14 and looking in the direction of the arrows.

Referring now specifically to the drawings, and initially to FIG. 1, there is shown a typical lockstitch sewing machine, generally designated by the reference numeral 30, which includes a machine table 32, bed plate 34 and machine body or head 36. The machine head 36 includes the usual main shaft which is driven at one end and is operative at the other or head end to actuate a needle bar (not shown) for reciprocating needle 38 (see FIG. 2) through its needle stroke in relation to the bobbin holder and hook assembly 40 which is mounted beneath the bed plate 34 and is rotated by hook shaft 42. The present bobbin changing mechanism, generally designated by the reference numeral 44, is constructed for use with a wide variety of conventional sewing machines of the type generally described herein and as exemplified by machines manufactured by Singer, Union Special, Brothers, Necchi, Pfaff and the like, such machines capable of providing Federal Stitch No. 301, commonly called a lockstitch. Accordingly, further description of such conventional sewing machines is deemed unnecessary for those skilled in this art and for an understanding of the present invention.

In this illustrative embodiment, the bobbin changing mechanism 44 is illustrated and described in conjunction with a rather elementary manual actuating system including hand crank 46 (FIG. 1) and a highly simplified runout signalling system (FIG. 6). However, it will be appreciated, as the description proceeds, that the present mechanism is particulary suited to be completely automated in response to the signalling of bobbin thread runout. In such a completely automated version, the change cycle will occur without operator intervention. The signalling system will disable the sewing machine during the bobbin changing cycle and the cycle will go forward to remove an empty bobbin case from the bobbin holder and replace the same by a bobbin case having loaded therein a new coreless bobbin, followed by the signalling of the machine operator that the machine has a replenished supply of bobbin thread and is conditioned for the next stitching interval at the end of which the bobbin runout is again signalled and the bobbin changing cycle automatically repeated by the automated controls.

An overall understanding of the invention can be had by progressive reference to FIGS. 2 to 5 inclusive and the following description of the elements of bobbin changing mechanism 44 and its bobbin changing cycle. In these simplified diagramatic views, the bobbin changing mechanism 44 is seen to include a rotatable bobbin case the two 48 having opposed bobbin case receivers R1, R2 which move in succession from a case transfer position in axial alignment with the bobbin holder and hook assembly 40 and the hook shaft 42 to a bobbin loading position at a removed location. The mechanism 44 includes a case transfer mechanism 50 which includes a transfer member 52 which is operable along the axial path in'alignment with the hook axis between operative and retractive positions relative to carrier 48 and the assembly 40. In the illustrative position of FIG. 2, the sewing machine is running and has one of thetwo bobbin cases (X1) received within the holder and hook mechanism 40, with the other of the bobbin cases (X2) being supported on the carrier 48 at the bobbin loading position and containing therein a bobbin B2 which is fed into bobbin case X2 from the bobbin supply magazine 54. Magazine 54 is mounted to be in axial alignment with successive empty bobbin cases brought into the bobbin loading position such that it can feed successive coreless bobbins, such as leading bobbin B2, into the successively emptied bobbin cases X1, X2 which are brought into this loading position. During the normal running mode of the sewing machine, the bobbin thread BTl emerging from bobbin B1 in bobbin case X1 is monitored by a corresponding contact S1 (see FIG. 6) in the illustrated and highly simplified signalling device 56 which includes energizing source 56a, main switch 56b, step-down transformer 56c and indicator bulb 56d. The secondary of step-down transformer 60 is grounded at 56c as is the particular bobbin case X1 at 56f such that upon runout of the bobbin thread BTl, the operator is signalled by light 56d to initiate the bobbin changing cycle by turnbase wallof the empty bobbin case Xl. Thereupon, the

transfer member 52 is turned to lock the transfer head within the bobbin case such that upon thereturn stroke thereof (compare FIGS. 3 and 4) the empty bobbin case X1 is retracted from the bobbin mechanisms 40 of the sewing machine and loaded into the aligned and previously empty receiver of the carrier (see FIG. 3). The transfer member 52 then is released from the transferred empty bobbin case X1 and moved to a clearance position relative to carrier 48 on the side thereof remote from the bobbin mechanism 40, as illustrated diagramatically and indicated by the several arrows on transfer member 52 in FIG. 4. Thereupon the carrier 48 turns through (compare FIGS. 4 and 5) to bring empty bobbin case X1 into alignment with the bobbin supply magazine 54 (see FIG. 5) and concur rently the loaded and waiting bobbin case X2 is moved to the case transfer position. The FIG. 5 showing illustrates bobbin X2 already moved from the case transfer position supported on carrier 48 by the next forward stroke of transfer member 52 into the holder and hook assembly 40 of the sewing machine. The transfer member 52 then moves through its return stroke, as indicated by the directional arrow in FIG. 2, into the retracted position relative to bobbin holder and hook assembly 40 and the bobbin changing apparatus 44 is once again in the standby position shown diagramatically in FIG. 2. In such standby position, the sewing machine has been loaded and is running with a full bobbin case X2; and the mechanism 44 has its empty receiver R2 aligned with assembly 40, with the other bobbin case X1 waiting in the bobbin loading position for the next bobbin changing cycle.

With the foregoing general understanding of the overall mechanisms and sequence of operations during a typical bobbin changing cycle, reference will now be made to the detail showing in the remaining figures for a description of the specific construction of a typical bobbin changing mechanism which is preferably constructed to be mounted on the sewing machine as an attachment which may be suspended from the machine by replacing the slide plate thereof. As seen best in FIG. 14 and as is generally understood, in a conventional sewing machine, the bed plate 34 includes a stationary throat plate 34a provided with the required feed dog slots (not shown) and needle hole 34b through which needle 38 reciprocates during the normal operation of the sewing machine. Rather than the conventional sewing machine slide plate, there is provided a combined slide and mounting plate 60 which is received within a slide plate guideway 340 (see FIGS. 17 to 20) such that slide plate 60 may be moved toward and away from throat plate 340, as may be required from time to time in the servicing of the sewing machine. Slide plate 60 may be locked into position on the bed plate 34 of the sewing machine in any convenient fashion, as by the provision of one or more mounting screws 62 (see FIG. 20) which extend through top mounting plate 64 and are tapped into the lock plate or bar 66, which is drawn up against the underside of the feed bed 34 upon tightening of the mounting screws 62. Top plate 64 is part of a frame or chassis 68 which includes spaced and parallel front and rear mounting

plates

70, 72 connected by a bottom plate 74. The front mounting plate 70 is spaced in relation to the bobbin holder and hook mechanism 40 to provide adequate space for the carrier or bobbin changing carrier or shuttle 48 which is journalled for rotation about a hori zontal carrier axis which is offset from, spaced below and parallel to the axis of hook shaft 42. In this illustrative embodiment, the mechanism or attachment 44 includes a main shaft 76 which is appropriately journalled on the back mounting plate 72 and has attached thereto the main actuating cam 78 which in the form of a barrel cam extending from the back mounting plate 72 through the central cutout 70a in the front mounting plate 70 which is also provided with an enlarged well 70b. The main actuating cam 78 is provided with an axial and integral hub 80 extending beyond plate 70 on which hub the carrier 48 is journalled. The carrier is held on hub 80 in any convenient fashion, such as by lock washer 82 and nut 84. Thus, both the carrier 48 and the main cam 78 are capable of turning on the common axis afforded by shaft 76. The carrier 48 and main cam 70 thus are mounted for rotation relative to each other and for movement in unison (when carrier 48 is coupled to the main actuating cam 78) as will be subsequently described. This construction is necessary in this illustrative embodiment since the bobbin changing mechanism 44 is designed with an operating cycle in which main cam 78 rotates through 360 and carrier 48 rotates only during approximately 180 of cam rotation.

The mechanism 44 is actuated via the main cam 78 through the provision of a main driving sprocket 86 which is pinned to shaft 76 and is connected via chain 88 to the actuating sprocket 90 (see FIG. 1) which is on actuating shaft 92 carrying hand crank 46. Thus, in response to turning of hand crank 46, main shaft 76 rotates the barrel cam 78 to initiate and complete a bobbin changing cycle. Provision may be made in the manual actuating mechanism to permit the turning of shaft 76 only in the particular direction for which the mechanism 44 is designed; and appropriate detents, etc. may be provided such that the manual drive is decoupled at the end of a bobbin changing cycle to avoid a situation wherein the operator inadvertently goes beyond the requisite 360 of rotation to the main cam 78. Also, as previously indicated, this simple manual actuating mechanism may be replaced by an automated control in which an appropriate fractional horsepower motor would be mounted directly on shaft 76 (at the location of drive pulley 86), with the motor being connected in an appropriate motor control including the bobbin runout sensors (see FIG. 6).

In this illustrative embodiment, which is constructed to employ two bobbin cases, each of which is successively loaded with a coreless and cheekless bobbin (i.e. B1, B2), there are provided two bobbin receivers or seats R1, R2 circumferentially spaced at 180 relative to each other on carrier 48. The receivers are of identical construction and are constructed to snugly receive and support the bobbin cases for movement from the bobbin loading position removed from the hook axis to the case transfer position along that axis and to permit operation of the transfer mechanism 50 including the transfer member 52. Since the bobbin receivers R1, R2 are constructed to receive somewhat modified bobbin cases X1, X2, it will be useful to first described the modified bobbin case, seen best in FIGS. 7 to 9 inclusive. In the modified bobbin case construction suitable for both cases X1 and X2, bobbin case 94 has a cupshaped bobbin case body 96 which includes a cylindrical body wall 98 terminating at one end in a case opening 100 through which the bobbin B is loaded and terminated and closed at the other end in a base wall 102 which is curved in the usual fashion. In the curved base wall 102 contiguous with its junction with the adjacent end of the cylindrical body wall 96 and at the 12 oclock position on the bobbin case 94, there is provided the usual needle hole 104. Rather than providing the bobbin thread tensioning spring at approximately the 11 oclock position, as is conventional, the modified bobbin case 94 is provided with a bobbin thread tensioning and guiding mechanism at a diametrically opposed location corresponding approximately to 6 o" clock. This mechanism includes a V-shape cut 106 (see FIG. 9) in the cylindrical body wall 98 which extends inwardly from case opening 100 and terminates at its apex in a throat 108 through which the bobbin thread emerges (see FIGS. 7 and 8). The contiguous portion of the curved base wall 102 is provided with a radial guideway 110 in the same plane as the throat 108 through which the bobbin thread is guided between base wall 102 and the adjacent sensor or contact S. The bobbin thread tensioning and guiding mechanism is completed by the provision of tensioning spring 112 having the usual adjustment screw 114. As described in copending application Ser. No. 136,706, filed Apr. 23, 1971, entitled Bobbin Runout Signalling Device, the emergence of the bobbin thread BT at the 6 oclock location and at a point substantially removed from the needle hole 104 and the coacting sensor S provides a bobbin runout signal with a reasonable length of bobbin thread remaining and available for continued stitching until the operator (or an automatic control) is capable of responding to the bobbin runout signal to discontinue the stitching operation. Thus there is the reasonable assurance that the stitching operation will be discontinued without interrupting the continuity of the stitch, as illustrated in FIG. 10, and enabling the stitch to be resumed as progressively illustrated in FIGS. 1 1 to 13, with the remainder btl of the exhausted bobbin thread BTl captured in the stitch line as the stitching operation is resumed with the replenished bobbin thread BT2. It will be appreciated that the FIG. 13 showing is on a greatly exaggerated scale and that in the typical stitched assembly, there will be very little tell-tale trace along the stitch line length wherein there is an overlap of bobbin threads at the underside of the stitched assembly. Of course, any tell-tale presence of the bobbin thread, such as the beginning bt2 of the next bobbin shown in FIG. 13 can be trimmed. As may also be appreciated from inspecting FIGS. 11 and 12, the beginning bt2 of the replenishing bobbin thread BT2 is automatically engaged beneath the sensor at the commencement of the stitching operation and interengaged with the needle thread NT at the time the stitching operation is resumed.

Continuing with the description of the modified bobbin case 94, it would be appreciated that the usual bobbin spool keeper mounted on the curvedbase wall 102 is eliminated and this wall is constructed with a simple keyhole shaped slot 116 through which the head of the transfer member 52 is inserted for withdrawing the empty bobbin case" from the bobbin holder, as illustrated diagramatically in FIGS. 3 and 16 and as willbe more fully described. Finally, the bobbin case 94 is provided on the cylindrical body wall 98 with diametrically

opposed guideways

118, 120 which extend lengthwise of wall 98, are arranged at the 3 oclock and 9 oclock positions respectively and are adapted to receive corresponding holding springs provided in the bobbin receivers R1, R2 of the carrier or shuttle 48 and also in the bobbin holding and hook mechanism 40.

Now to a description of the identical bobbin case receivers R1, R2, as seen best in FIGS. l4, l6 and 17, receiver R1 includes a circular seat 122 which is of a depth corresponding substantially to the depth of cylindrical body wall 98 and of a diameter to snugly accommodate bobbin case 94. The bottom of the seat 122 is relieved away, as indicated at 124, to provide a curved shoulder against which an annular segment of the curved base wall 102 rests. The curved shoulder 124 terminates in through opening 126 to the backside of the carrier 48. Opening 126 provides the necessary clearance for the transfer member 52 to pass during the forward and return strokes thereof when an empty bobbin case is removed from the assembly 40 and the transfer member moves to the clearance position illustrated in FIG. 4 and when the transfer head moves through its forward stroke to push a reloaded bobbin case back into the assembly 40 as illustrated in FIG. 5. The construction of the respective bobbin case receivers R1, R2 is completed by the provision of diametrically

opposed springs

128, 130 which are engaged respectively in the guide ways or slots 118, and extend lengthwise of circular seat 122. Appropriate clearances are provided behind the respective springs 128, such that they may function to engage the bobbin case at the 3 oclock and 9 oclock positions, both in the bobbin loading position as exemplified by the loaded bobbin case X2 in FIG. 17 and during movement to the case transfer position as substantially. shown in FIG. 18.

Based upon an understanding of the modified bobbin case and the manner in which it is held in carrier 48, it will be appreciated that the otherwise conventional bobbin holder and hook assembly 40 of the conventional machine must also be modified. As seen best in FIG. 14 and in the severalprogressive showings of FIG. 16, assembly 40 includes a conventional revolving hook 40a which rotates with hook shaft 42 and is provided with raceway 40b which receives a modified bobbin holder 40c held stationary by the conventional keeper 40d and provided with diametrically

opposed spring fingers

128, 130 received respectively in bobbin case guide ways 118', 120'. This arrangement holds the bobbin case 94 in a stationary position relative to the bobbin holder 400, with this subassembly being held stationary as bobbin hook 40a rotates under control of book shaft 42 in the conventionallmanner to interengage the needle thread NT and the bobbin thread ET in the usual fashion, as shown diagramatically in FIGS. 10 to 12 inclusive.

As seen best in FIG. 14, the bobbin supply magazine 54 is stationary and includes an elongated and cylindrical magazine body 54a which terminates at one end in an exit opening 54b coextensive and in axial alignment with the successive receivers R1, R2 which are brought into the bobbin loading position and is closed at its opposite end by a base wall 54c. The magazine 54 is removably mounted to extend with its axis parallel to and spaced from the axis of the hook shaft 42 on a mounting bracket 132 on thebottom plate 74 of the frame 68. The magazine 54 contains the plurality of toroidal coreless wound bobbins disposed one behind the other and in axial alignment witheach other, with the successive bobbins in the magazine being designated as B3, B4, B5, etc. Each of the bobbins is of identical construction. Representative bobbin, designated by thenumere] 134, is seen to include plural bobbin thread convolutions packed to provide a toroidal body 134a having a substantially cylindrical outer peripheral wall terminating at one end in a leading face 134!) which is curved to conform generally to the curved base wall 102 of the bobbin case 94 and at its opposite end in a planar trailing face 134a. Each of the bobbins is interconnected by a continuation of the bobbin thread of the leading one of the bobbins which emerges from the inner periphery thereof at its leading face (i.e. face 1314b), extends over its outer peripheral wall and the outer peripheral wall of the next adjacent and trailing bobbin and merges with the toroidal body of the trailing bobbin at its trailing face. The thread continuation between leading bobbin B2 and trailing bobbin B3 is representative and designated by the reference numeral 136. Successive continuations (i.e. continuation 136) will provide the requisite bobbin tails between successive bobbins fed into the sewing machine (i.e. tail bt2 in FIGS. to 12). Behind the stack of bobbins within magazine body 54a, there is disposed a spring 138 which is seated against base wall 54c and continuously urges successive leading bobbins into the empty bobbin cases 94 in the receivers R1, R2 which are successively presented at the bobbin loading position in response to each 180 index of the carrier 48.

Reference will now be made to FIGS. 14 to 16 inclusive for a description of the bobbin case transfer mechanism 50 which is operable during approximately the first 90 of rotation of the main actuating cam 78 to withdraw the empty bobbin case from the bobbin holding and hook assembly 40 and during approximately the last 90 of the bobbin changing cycle to load the next full bobbin case into the assembly 40 and to thereafter retract for running of the sewing machine. The case transfer mechanism 50 includes the transfer member 52 which includes an elongated cylindrical body 52a which is mounted for axial sliding movement in alignment with hook shaft 42 on the front and back mounting

plate

70, 72. Toward its trailing end, body 52a is provided with an elongated follower keyway 52b which receives cam pin 52c on back plate 72. Follower keyway 52b and cam pin 52c cooperate to rock transfer member 52 through a limited angle at the forward limit of its axial reciprocation to lock the same to an empty bobbin case for its withdrawal from assembly 40 as will be described. Intermediate its ends, the transfer member body 520 carries a cam follower head 52d which is supported between collars 52e, 52f fixed to the body and extends into the cam track 78a on main cam 78. Follower head 52d is held against rotation by also slidably mounting the same on slide pin 521 (see FIG. 20) on frame 68. Projecting from the forward end of body 52a is mounting stern 52g which at its leading end carries a traverse case engaging pin 52h which is dimensioned to fit through keyhole slot 1 16 in the bobbin case (see FIG. 7) and to be locked within the case upon rocking of member 52 (see FIG. 8). Behind pin 52h is a case pusher head 52i which has a concavely curved front face adapted to engage and bear against the outer surface of the curved base wall 102 of the bobbin case 94 during the forward case inserting stroke of member 52 (see FIG. 8). Head 52i is mounted on stem 52g with a back-up spring 52j therebehind which provides a resilient cushioning mount for head 52i.

Reference will now be made to the illustrative cam development of FIG. 15 and to the diagramatic showing of FIG. 16 for an explanation of the function of the bobbin case transfer mechanism 50 which is functional during the beginning and end of a bobbin changing cycle of the machine. During the normal running of the sewing machine, the transfer mechanism 50 is in the standby position A (corresponding to FIGS. 2 and 14), with member 52 retracted and in a rotational attitude such that the transverse pickup pin 52h is oriented to enter the keyway slot 116 in bobbin case 94.

The rise portion of cam track 78a between positions A and B (FIG. 15) is such as to advance the transfer member 52 through a forward stroke to the bobbin case pickup position B (corresponding to FIG. 3); and after pickup pin 52h enters the bobbin case, it is rotated due to the camming action of pin 520 in cam slot 52b to lock pin 52h within the bobbin case 94 against the inner surface of base wall 102. The cam development of track 78a between position B and position C (see FIG. 15) is such as to cause the transfer member 52 to move through its retracting stroke, with the coacting pin 52c and cam slot 52b at the opposite extremity being arranged to rotate member 52 to disengage pin 52h from bobbin case 94 after the latter is seated in receiver R1 of carrier 48. Thereupon, the pin 52h is aligned relative to slot 116 and may be disengaged therefrom such that the transfer member 52 may be retracted relative to the bobbin case and moved to the clearance position C. During the next 180 of rotation of main cam 78, cam follower 52d is in the dwell portion of cam track 78a during which time carrier 48 is rotated through 180 to bring receiver R2 into a bobbin case transfer position (not shown but corresponding generally to the FIG. 18 position). Thereupon, the rise portion of the cam track 78a between position D and position E is such as to advance the transfer member 52 from the retracted clearance position C through its forward stroke. During the first portion of the forward stroke, the pusher head 52i engages the exterior of base wall 102 to thrust the loaded bobbin case X2 forwardly from receiver R2 and into the empty bobbin holder, with the forward position of pusher head 52i corresponding to the case loading position E. It is to be noted that in such case loading position, the degree of forward movement of the transfer member 52 is somewhat less than that in the case pickup position B since it is not necessary for the pickup pin 52h to enter the bobbin case during the case loading stroke. The final cam development between position E and position A is such as to return the transfer member 52 to the standby position for the normal running mode of the sewing machine While the transfer mechanism 50 is in the retracted clearance position commencing at position C on the cam development and for the next 180 of the cam rotation, it is inactive and the transfer mechanism 50 is clear of the carrier 48. At this point, the carrier has an empty bobbin case in one receiver (i.e. receiver R1) and a loaded bobbin case in the other receiver (i.e. receiver R2). During this second 180 of cam rotation, provision is made for coupling carrier 48 to main cam 78 to index carrier through 180' to bring the empty bobbin case to the bobbin loading position removed from the bobbin holder and hook assembly 40 and to bring the loaded bobbin case to that position for reloading of the sewing machine. Coupling of the main actuating cam 78 to the carrier 48 is accomplished by the cam operated coupling mechanism, seen best. in FIGS. 14, 19 and 20. This cam actuating coupling mechanism includes coupling pin which is mounted on main cam 78 for longitudinal movement along a path parallel to and radially offset from shaft 76. The trailing end of pin 140 extends into a clearance bore 78c which opens into an annular well 78d formed in the rearward end of the cam 78. Within the well 78d there is mounted a face cam 142 which has a progressive annular rise arranged to drive coupling pin 140 forwardly through well 78e at the forward end of cam 78 and into one of two diametricaly opposed coupling slots 48a, 48b formed on the adjacent face of carrier 48. Coupling pin 140 is biased against face cam 142 by biasing spring 140a seated within clearance bore 780 and bearing against cam 78 at one end and against a washer l40b pinned to coupling pin 140. When the bobbin transfer mechanism is in standby position A, the coupling pin 140 is approximately at the 6 oclock position as seen in FIGS. 14 and 19 (position A being specifically designated in FIG. 19). In response to clockwise rotation of the main cam 78, as indicated by the directional arrow in FIG. 19, coupling pin 140 moves along a circular path until it confronts the slot 480; and under bias of spring 140a, it enters slot 48a and moves through a lost motion until the coupling pin seats itself against the end of slot 48a. This occurs approximately at the 9 oclock position and corresponds to the transfer mechanism 50 being in the retracted clearance position C. Continued rotation of cam 78 and coupling pin 140 in the clockwise direction will cause carrier 48 to turn through 180, bringing coupling slot 48a into the position occupied by coupling slot 48b in FIG. 19. Correspondingly, this brings coupling slot 48b into the position occupied by coupling slot 48a to thereby index the carrier 48 through 180. Thereupon, the develop ment of face cam 142 permits the coupling pin 140 to retract from coupling slot 48a to decouple carrier 48 from the actuating cam 78a in the indexed position until the next bobbin changing cycle. Decoupling occurs at approximately position D on the cam development (see FIGS. 15 and 16) such that the rise portion of cam track 78a will be operative to advance the transfer member 52 relative to the indexed, but stationary carrier in which a loaded bobbin case is presented for axial transfer into the bobbin holder and hook assembly 40. As the main cam 78 completes the final portion of its rotation, corresponding to the loading of the bobbin case, the coupling pin 140 returns to the 9 oclock position awaiting the next carrier indexing sequence which will occur during the next bobbin changing cycle,but with coupling pin 140 entering the indexed coupling slot 48b.

Appropriate detent mechanisms may be provided, as is generally understood by those skilled in the art, to releasably lock variousparts of the mechanism in their respective indexed positions. For example, and as seen in FIG. 20, follower 52d on transfer member 52a may be provided with a spring biased ball 52k engaged in one or the other of the ball recesses on member 52a to successively lock member 52 in the rotational position wherein transverse pickup pin 52h is aligned with keyhole slot 16 in bobbin case 94 and in the indexed rotational position in the locked or pickup position relative thereto. In similar fashion, a detent mechanism may be associated with the carrier 48 to lock the same in one or the other of its indexed positions wherein the successive loaded bobbin cases are presented in alignment with assembly 40 fortransfer thereto- Mounted on carrier 48 are two thread runout sensors S1, S2 associated respectively with bobbin case receivers R1, R2. The thread runout sensors are disposed in succession in positions to bear against the bobbin case 94 on the base wall 102 contiguous to thread guide slot 110 (as shown in FIGS. 2, 6 and 14) during the normal running mode of the sewing machine. However, during the bobbin changing cycle, the respective thread sensors S1, S2 must be retracted to a non-sensing position relative to the holder 40c of assembly 40 to permit the withdrawal of the empty bobbinv case and the replacement of the same with the loaded bobbin case, followed by the return of the respective sensors to the sensing position for the next running mode or stitching interval of the sewing machine. Since the construction of the respective sensors S1, S2 and their movement between the sensing or operative position and the non-sensing or retracted position is the same, it will suffice to describe only one of the sensors and its related mechanisms in detail. For example, as seen best in FIGS. 14 and 17 to 19; sensor S1 includes a resilient contact blade 144 which is pivoted on carrier 48 at blade pivot 146 which extends parallel to and is spaced below the aligned hook shaft 42 and the transfer member 52. Blade pivot 46 is received within an insulating sleeve 148 and extends through carrier 48 to the rearward face thereof (see FIG. 19) at which it carries a cam follower 150 which is biased by spring 152 anchored and insulated on carrier 154 to normally pivot the contact blade 144 to the sensing position. As previously indicated, the adjacent face of the main cam 78 is provided with a well 78e which accommodates the rearward end of blade pivot 146 and the cam follower 150. The well 78e is surrounded by an annular flange 78f of the main cam 78 which is constructed of an insulating material. As seen in FIG. 19, an annular segment of the electricallyinsulating flange 78e is provided with a conductive insert 156 which is disposed in the sector which confronts cam follower 150 when the bobbin changing mechanism 44 is in its standby condition during the normal running mode of the sewing machine. The inner surface of the conductive insert 156 is provided with a cam cut- I out 156a which permits the cam follower 150 under influence of spring 152 to turn the contact blade 144 of the corresponding sensor into its operative or sensing position. However, in response to rotation of the cam 78 in its operative clockwise direction (as shown in FIG. 19), the follower 150 rides up onto the continuous peripheral camming surface afforded by the cylindrical surrounding wall of well 78e to turn the cam follower 150, blade shaft 146 and contact blade 144 into the retracted position removed from the assembly 40 and oriented to permit the unobstructive functioning of the bobbin changing mechanism during its functional cycle.

While the main cam 78 is in its stationary starting po-' sition shown in FIGS. l4, l7 and 19 with the case transfer mechanism 50 in the standby position and the particular sensor blade 144 bearing against the bobbin case 94, provision is'made for completing the requisite connection from that blade to the control circuit shown in FIG. 6. This simply lights bulb 560! over the secondary of transformer 560 to ground.56e when the bobbin thread runs out. However, in a more sophisticated circuit, this could initiate an automatic change cycle and disable the sewing machine for the duration of that cycle. The circuit is completed by the mounting on front frame plate of an insulated brush 158 which is spring biased against the outer periphery of conductive insert and also bears against the outer periphery of flange 78fduring rotation of main cam 78. Contact brush 158 is connected by an appropriate lead wire 160 into the simplified circuit shown in FIG. 6.

Provision is made on the indexab le carrier 48 and the stationary bobbin feeding cartridge 54 for severing successive intermediate lengths of thread (i.e., length bt2 in FIGS. 10 to 12) as the loaded bobbin case is indexed from the remote bobbin loading position to the case transfer position and to also guide the length of bobbin thread being drawn during the indexing operation. In this illustrative embodiment, this is accomplished by providing on the flat inner face 48d of carrier 48 a central projecting thread guide flange 48c which is formed with a circumferentially extending V-shaped thread guide 48c (see FIG. 14). Accordingly, as the loaded bobbin case is indexed through its 180 travel relative to the cartridge 54, the particular bobbin being indexed (i.e., bobbin B2) is moving away from the next bobbin to be loaded (i.e., bobbin B3) and the thread continuation 136 therebetween is lengthened, as by thread being drawn from the flat trailing face of bobbin B3. During this sequence, the lengthening thread continuation 136 extends within a portion the V-shaped thread guide 48c betwhen the 6 oclock and 12 oclock positions. After drawout of the interconnecting length of bobbin thread 136, cut-off is accomplished by mounting on the flat annular segment 48d of carrier 48 of

movable cutters

162, 164 which cooperate with a stationary cutter 166 which is mounted on the leading end of magazine 54 in position to coact, in succession, with the moving

cutter blades

162, 164. The successive coaction between

cutter blades

162, 164 with the stationary cutter 166 may be best appreciated by progressively considering FIGS. 17 and 18. FIG. 17 shows cutter blade 162 in its normal stationary and starting positions at the beginning of a bobbin changing cycle, while FIG. 18 illustrates that cutter blade having turned counter-clockwise through approximately 180 to its position for cut-off of bobbin thread continuation bt2 drawn incident to the advancement of bobbin B2 in case X2 toward the case transfer position in alignment with assembly 40. In this illustrative mechanism and as may be appreciated by considering FIG. 18, the cut-off of the thread continuation bt2 occurs, slightly in advance of the loaded bobbin case coming to rest in. the indexed case transfer position. Once cut-off is accomplished, the indexed bobbin case containing the loaded bobbin is free to be loaded into the assembly 40 by the operation of the actuating mechanism 50, as previously described.

A typical sequence of installation and operation will now be described in order to facilitate a more complete understanding of the present invention:

In order to equip the sewing machine 30 with the bobbin changing mechanism 44 of the present invention, the usual slide plate of the sewing machine is removed and replaced with the slide plate 60 of the chassis 68 and is locked in position by tightening down of the mounting screws 62. The otherwise conventional sewing machine is modified to replace the conventional bobbin holder with the modified bobbin holder 40c. The requisite supply of bobbins 134 is placed into the magazine 54, with the leading bobbin being biased into the aligned bobbin case which is of the modified construction shown in FIGS. 7 to 9 inclusive. The appropriate control is associated with the sewing machine 30. This may require modification of the motor control if the more advanced version of control is desired in which the sewing machine is disabled during the bobbin changing cycle and the cycle is automatically initiated in response to the runout of the bobbin supply in assembly 40. Finally, the mechanism is placed into the illustrated mode for normal running of the sewing machine in which a loaded bobbin case is mounted within the bobbin holder 400 of assembly 40.

Thereupon, the sewing machine 30 is equipped for the completely automatic or semi-automatic change of bobbins, with the bobbin change being indicated by the lighting of signal light 56d. In this illustrative embodiment, this is followed by the operator manually manipulating hand crank 42 to initiate and complete the bobbin changing cycle. At the end of the bobbin changing cycle, and with the bobbin thread coming underneath the sensor in the control illustrated in FIG. 6, the signal light 56d is extinguished thereby advising the operator that the machine has been replenished with the requisite bobbin supply whereupon the operator proceeds with the next stitching interval or sequence.

Since the stitching operation upon bobbin thread runout is detected with a length or tail of bobbin thread available beneath the fabric assembly (see FIG. 10), and in view of the operation of the bobbin changing mechanism, there is a high order of assurance that the stitch line will have no discontinuities nor tell-tale evidence of bobbin runout and the subsequent automatic replenishment. In its preferred form, the bobbin changing mechanism is an attachment which may be easily installed on any sewing machine by simply replacing the otherwise conventional bobbin holder and employing the modified bobbin cases associated with the mechanism. It will be appreciated, however, that the mechanism could be incorporated into the basic sewing machine design by the sewing machine manufacturer as original equipment. Insofar as the bobbin supply is con cerned, the illustrated and described supply is preferred in that the coreless and cheekless bobbins of the described configuration facilitate a highly reliable change mechanism and cycle, and also maximize the bobbin thread supply for the particular bobbin case design.

What we claim is:

1. An automatic bobbin changing mechanism for a sewing machine of a type utilizing a bobbin case containing a wound bobbin, a bobbin holder and a rotating hook, said wound bobbin being received within a bobbin holder for engagement of the bobbin thread by a hook rotating on a hook axis comprising a support adapted to be mounted on said sewing machine, a carrier mounted on said support for rotation about a carrier axis extending parallel to and offset from said hook axis, said carrier including at least two bobbin case receivers at circumferentially spaced locations and each adapted to receive a bobbin case for transfer between a bobbin loading position at a removed location from said bobbin holder and a case transfer position at a confronting location in alignment with said bobbin holder, bobbin loading means at said removed location adapted to receive a supply of coreless bobbins for feeding one of said coreless bobbins into an empty bobbin case in said bobbin loading position, means for indexing said carrier to bring the loaded bobbin case into said case transfer position, case transfer means movable relative to said carrier and operable when the loaded bobbin case is in said case transfer position to disengage the loaded bobbin case from its receiver and transfer the same into said bobbin holder of said sewing machine, sensing means operable when said sewing machine is running to detect the runout of bobbin thread in the loaded bobbin case in said sewing machine and means operable in response to said sensing means to disengage the empty bobbin case from said bobbin holder and return the same to the receiver at said case transfer position for movement to said bobbin loading position for reloading the empty bobbin case from said supply.

2. A mechanism according to claim 1 wherein said carrier includes two receivers circumferentially spaced at approximately 180 relative to each other and said mechanism is operable with two bobbin cases which are loaded in succession and then transfer to and from said bobbin holder during a bobbin changing phase of the mechanism cycle.

3. A mechanism according to claim 1 wherein said sensing means bears against the loaded bobbin case while said sewing machine is running to detect the runout of the bobbin thread and including means for moving said sensing means to a retracted position prior to operation of the means which disengages the empty bobbin case from said holder.

4. A mechanism according to claim 1 wherein the supply of bobbin is interconnected by a length of bobbin thread and including means for cutting said length after loading the leading one of the bobbin into an empty bobbin case at said bobbin loading position.

5. A mechanism according to claim 4 wherein the means for cutting is operable approximately at the time the loaded bobbin case moves into said case transfer position.

6. A mechanism according to claim 4 wherein the means for cutting includes a movable cutter for each bobbin case receiver and a stationary cutter coacting in succession with said movable cutters.

7. A mechanism according to claim 1 wherein said case transfer means includes a transfer member mounted for reciprocal movement along a path in axial alignment with said hook axis and including first means for engaging an empty bobbin case in said bobbin holder and withdrawing the same into an empty one of said case receivers on said carrier and second means for thrusting a loaded bobbin case from a loaded one of said case receivers into said bobbin holder.

8. A mechanism according to claim 7 wherein said case transfer member is movable during its operating sequence through successive case receivers in said case transfer position and is retracted to a clearance position relative to said carrier during indexing thereof.

9. A mechanism according to claim 1 wherein said support is in the form of a slide plate adapted to replace the conventional slide plate of the sewing machine to suspend said mechanism in operative relation to said bobbin holder.

10. An automatic bobbin changing mechanism for a sewing machine of the type utilizing a bobbin case containing a wound bobbin, a bobbin holder and a rotating hook, said wound bobbin being received within a bobbin holder for engagement of the bobbin thread by a hook rotating on a hook axis comprising a support adapted to be mounted on said sewing machine, a carrier mounted on said support for indexing movement, said carrier including at least two bobbin case receivers each adapted to receive a bobbin case for transfer between a bobbin loading position at a removed location from said bobbin holder and a case transfer position at a confronting location in alignment with said bobbin holder, bobbin loading means at said removed location adapted to receive a supply of bobbins for feeding bob bins one at a time into empty bobbin cases in said bobbin loading position, means for indexing said carrier to bring the loaded bobbin case into said case transfer position and case transfer means including a transfer member mounted for reciprocal movement relative to said carrier and including first means for engaging an empty bobbin case in said bobbin holder and withdrawing the same into an empty one of said case receivers on said carrier and second means for thrusting a loaded bobbin case from a loaded one of said case receivers into said bobbin holder of said sewing machine.

11. A mechanism according to claim 10 including sensing means operable to detect the runout of the bobbin thread in the loaded bobbin case in said sewing machine and means operable in response to said sensing means to disengage the empty bobbin case from said bobbin holder and return the same to the receiver at said case transfer position for movement to said bobbin loading position for reloading the empty bobbin case from said supply.

12. A mechanism according to claim 10 wherein said support is in the form of a slideplate adapted to replace the conventional slide plate of the sewing machine to suspend said mechanism in operative relation to said bobbin holder.

13. A mechanism according to claim 10 wherein said carrier includes two receivers circumferentially spaced at approximately relative to each other and said mechanism is operable with two bobbin cases which are loaded in succession and then transfer to and from said bobbin holder during a bobbin changing phase of the mechanism cycle.

14. A mechanism according to claim 11 wherein said sensing means bears against the loaded bobbin case while said sewing machine is running to detect the runout of the bobbin thread and including means for moving said sensing means to a retracted position prior to operation of the means which disengages the empty bobbin case from said holder.

15. A mechanism according to claim 10 wherein said case transfer member is movable during its operating sequence through successive case receivers in said case transfer position and is retractedto a clearance position relative tosaid carrier during indexing thereof.

Claims

2. A mechanism according to claim 1 wherein said carrier includes two receivers circumferentially spaced at approximately 180* relative to each other and said mechanism is operable with two bobbin cases which are loaded in succession and then transfer to and from said bobbin holder during a bobbin changing phase of the mechanism cycle.

10. An automatic bobbin changing mechanism for a sewing machine of the type utilizing a bobbin case containing a wound bobbin, a bobbin holder and a rotating hook, said wound bobbin being received within a bobbin holder for engagement of the bobbin thread by a hook rotating on a hook axis comprising a support adapted to be mounted on said sewing machine, a carrier mounted on said support for indexing movement, said carrier including at least two bobbin case receivers each adapted to receive a bobbin case for transfer between a bobbin loading position at a removed location from said bobbin holder and a case transfer position at a confronting location in alignment with said bobbin holder, bobbin loading means at said removed location adapted to receive a supply of bobbins for feeding bobbins one at a time into empty bobbin cases in said bobbin loading position, means for indexing said carrier to bring the loaded bobbin case into said case transfer position and case transfer means including a transfer member mounted for reciprocal movement relative to said carrier and including first means for engaging an empty bobbin case in said bobbin holder and withdrawing the same into an empty one of said case receivers on said carrier and second means for thrusting a loaded bobbin case from a loaded one of said case receivers into said bobbin holder of said sewing machine.

13. A mechanism according to claim 10 wherein said carrier includes two receivers circumferentially spaced at approximately 180* relative to each other and said mechanism is operable with two bobbin cases which are loaded in succession and then transfer to and from said bobbin holder during a bobbin changing phase of the mechanism cycle.

15. A mechanism according to claim 10 wherein said case transfer member is movable during its operating sequence through successive case receivers in said case transfer position and is retracted to a clearance position relative to said carrier during indexing thereof.