US3675603A

US3675603A - Sewing machine convertible from lock stitch to chain stitch

Info

Publication number: US3675603A
Application number: US38734A
Authority: US
Inventors: Chikao Yamashita
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1969-05-23
Filing date: 1970-05-19
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11
Also published as: JPS4918738B1

Abstract

A lock stitch sewing machine concurrently capable of carrying out chain stitching, namely, performing lock stitching when fitted with a throat plate adapted for said stitching and chain stitching when provided with another throat plate suitable for said stitching.

Description

1 1 July 11,1972

United States Patent Yamashita [56] References Cited UNITED STATES PATENTS [$4] SEWING MACHINE CONVERTIBLE FROM LOCK STITCH T0 CHAIN STITCH [72] inventor:

Clriimo Yamashita, Aichi-ken, Japan [73] Assignee: Brother Kogyo Kahushikl Katha, Nagoyashi, Japan [22] Filed: May 19, 1970 Primary Examiner-James R. Boier Attorney-Kemon, Palmer & Eatabrook 211 App]. No.2 311,734

[30] Foreign Application Priority Data ABSTRACT machine concurrently capable of carrying namely, performing lock stitching when ate adapted for said stitching and chain stitching when provided with another throat plate suitable for Feb. 26,1970

a LM M Um HUM UUU 7Ciaims,24DrawlngFigures PATENTEDJIJL 1 1 m2 sum 01 or 11 M INVENTOR.

PATENTEDJUL 11 1972 3,675,603

sum 02 or 11 INVENTOR.

no, bvm I W PATENT'EDJUL 1 1 I972 3. 675.603

sum on u? 11 (A5; V/Alg 9 INVENTOR.

BY W INVENTOR SHEET 05 0f 11.

FIG.

PKTENTEDJUL 1 1 I972 MW,MW

PATENTEUJUL 1 1 I972 sum 06 0F 1 INVENTOR.

BY arnm/ W FIG. 12

PNENTEUJUL I 1 I972 3. 675.603

saw 07 or 11 I N VE N TOR.

PA'TENTEDJULH m2 3,675,603

SHEET 08 0F 11 INVENTOR.

P'ATENTEDJUL 1 I 1912 sum 10 or 11 INVENTOR.

PATENTCDJUU 1 I972 SHEET 11 0F 11 INVENTOR.

SEWING MACHINE CONVERTIBLE FROM LOCK STITCH 'IO CHAIN STITCH This invention relates to a sewing machine for lock stitching and more particularly to a machine also capable of chain stitching.

A sewing machine in common use is of a lock stitch type. It has been desired that the machine be also capable of forming chain stitches, if required. To meet this demand, there have been employed various types of chain stitch forming device. To convert the original lock stitch sewing machine to that of chain stitching, however, the bobbin case or its retainer of a rotary or oscillating type loop taker had to be replaced with parts adapted for chain stitching. A lock stitch throat plate had to be replaced with a different throat plate suited for chain stitching which had a long needle aperture extending in the direction in which there was fed a work fabric. Further the needle thread had to be passed through an auxiliary thread guide in order to reduce the quantity of the needle thread at the time of chain stitching. Thus replacement or operation of a large number of parts caused great trouble to a general household user of a sewing machine. Moreover, parts were likely to be lost and wrong operation led to the failure of chain stitching to be smoothly performed.

It is an object of the present invention to simplify the operation of switching from the lock stitching to the chain stitching or vice versa only by replacement of a first and second throat plate adapted for lock and chain stitching respectively.

A further object of the invention is to reduce the quantity of the needle thread released by a thread takeup mechanism when the second throat plate is fitted due to replacement and assure the smooth operation of a chain stitching device, thereby effecting the better performance of chain stitching.

The present invention provides a sewing machine equipped with a lock stitching device as well as with a chain stitching device co-operable therewith which is capable of lock stitching when fitted with a first throat plate adapted for said lock stitching and also chain stitching when fitted with a second throat plate suited therefor, thereby enabling switching from the lock to the chain stitching or vice versa to be realized simply by interchange of the first and second throat plates and offering great convenience to a general household user of a sewing machine.

Further, the present invention provides an easy operable sewing machine of simple construction which eliminates the necessity of replacing bobbins as has been required for the prior art sewing machine without causing any trouble to a general user of a sewing machine and yet is capable of being manufactured with ease and at low cost and always performing good chain stitching.

The present invention will be more fully understood from the following description taken with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an ordinary lock stitch sewing machine permitting the use of a chain stitching device according to an embodiment of the present invention;

FIG. 2 is a similar perspective view of FIG. 1 showing by a two dots-dash line a frame containing a loop taker rotatable about a horizontal axis parallel with the direction in which there is fed a work fabric;

FIG. 3 is an elevation of an entire chain stitching device where a thread loop released from a loop taker is retained by a loop retaining member;

FIG. 4 is a sectional view on line 4-4 of die chain stitching device of FIG. 3;

FIG. 5 is a plan view of the device of FIG. 3, taken from line $-5 thereof;

FIG. 6 is a sectional view on line 66 of the device of FIG.

FIG. 7 is a sectional view on line 7--7 of the device of FIG. 5;

FIG. 8 is a sectional view on line 88 of the device of FIG.

FIG. 9 is a sectional view on line 9-9 of the device of FIG.

FIG. 10 is a bottom plan view of the device of FIG. 7;

FIG. 11 is a perspective view of a first throat plate for lock stitching;

FIG. 12 is a perspective view of a second throat plate for chain stitching;

FIG. 13 is a bottom plan view of the second throat plate of FIG. I2;

FIG. 14 illustrates the condition in which there is pulled off the loop shown on line 14-14 of FIG. 4 in fragrnental en- Iargement;

FIG. 14a is a top view ofthe same;

FIG. 15 is a fragmental sectional view corresponding to FIG. 3 where the first throat plate is fitted to the frame;

FIG. 16 is a fragmental sectional view corresponding to FIG. 4 where the loop seized by the loop retaining member is released by the needle when it is brought down;

FIG. 17 corresponds to FIG. 3 where the thread loop seized by the loop taker is being broadened;

FIG. 18 is a side view of the device of FIG. 17; FIG. I9 is an elevation of the thread seizing member of FIG. 1

, FIG. 20 illustrates the condition in which the thread seizing member is brought to an operative position;

FIG. 21 shows the thread seizing member in an inoperative state; and

FIGS. 22 and 23 represent modifications of the thread seizing member, and FIG. 22 is an elevation thereof corresponding to FIG. ISI and FIG. 23 corresponds to FIG. 20.

There will now be described with reference to the appended drawings a chain stitching device according to an embodiment of the present invention.

The sewing machine of FIGS. 1 and 2 is an ordinary lock stitch type. A machine frame 20 has a cylindrical bed 22 with a work supporting surface mounted on a base 21. From the cylindrical bed 22 rises a standard 23 supporting a bracket arm 24 overhanging the bed 22. At the end of the cylindrical bed 22 is positioned the later described loop taker. To said end is movably fitted a cap member 25 so as to allow a bobbin case to be inserted into and taken out of the loop taker. A main drive shafl 26 joumaled lengthwise in the bracket arm 24 drives all the moving parts of the sewing machine and may be actuated by an electric motor, by a foot treadle or the like (not shown). A counterbalanced crank 27 on the main shaft 26 is operatively connected by means of a connecting rod 28 to a needle bar 29 endwise slidable along a support 30 pivotally secured at 31 on the bracket arm 24 and supporting at the bottom end a thread carrying eyed needle 32. A needle thread takeup lever 33 is also actuated by the crank 27 and constrained by an anchor link 34 so as to tighten and slacken the needle thread alternately in timed relationship with the endwise reciprocation of the needle 32. The path of the needle thread extends from a supply source (not shown) to a thread stretching device 35 through an eyelet 36 in the takeup lever 33, and then through appropriate guides such as a thread guide 37 on the needle bar 29 and finally to the needle eye. Such arrangement for controlling the needle thread is typical of that which is required for lock stitching.

Numeral 38 is a loop taker shaft mounted on the frame 20 rotatably about a horizontal axis parallel with the direction in which there is fed a work fabric 39. The loop taker shaft 38 is fitted at the end with a loop taker 41 carrying a loop seizing beak 40. The loop taker shaft 38 is connected to a lower shaft 44 through a set of

gears

42 and 43. The lower shaft 44 interlooks with the main drive shaft 26 through a timing belt 45, allowing die loop taker 41 to rotate twice for each reciprocation of the needle. The needle and loop taker are driven in such timed relationship that while the needle is brought down, the loop coming out of the needle eye is seized by the loop taker 41 and while the needle is lifted, the seized loop is released from the loop taker 41. To the loop taker 41 is fitted a bobbincase retainer 47 adapted to accommodate an ordinary bobbin case 46. At the front upper part of the loop retainer 47 is formed a recess 48 near the point through which the needle passes endwise. Numeral 49 represents a restraining member whose base end is fixed to the frame by screws 50. At the end of the restraining member 49 is formed a tongue 53 freely engaging the recess 48 so as to define an opening 52 therewith for permitting the passage of the released loop 51 released from the loop taker 41 pulled up by the thread takeup mechanism, thereby preventing the bobbin case retainer 47 from rotating with the loop taker 41.

In the cylindrical bed 22 is disposed the later described feed dog 54 perfonning the known four feed motions through the slot of the throat plate. The feed dot 54 advances the work fabric 39 on the work support in a prescribed direction during each endwise reciprocation of the needle 32. The feed dog 54 is fixed to a feed bar 56 connected to a feed advancing shaft 55. The feed advancing shaft 55 is made to swing by a twoforked rod 58 embracing a feed cam 57 on the main shaft 26, causing the feed dog 54 to make feed advancing and backward movements. The feed bar 56 is operatively connected to an oscillating shaft 61 actuated by a rod 60 embracing a feed lift eccentric 59 fixed to the main shafi 26. Rotation of the main shaft 26 raises the feed dog 54. lt will be appreciated that as it is conventional in the art, a mechanism for linearly feeding the work fabric 39 has a timed relationship to the reciprocation of the needle, so that while the needle 32 is lifted above the work fabric 39 on the throat plate, the feed dog 54 is lifted and advanced and while the needle descends, the feed dog 54 is brought beneath the throat plate back to its original position. Numeral 62 denotes an operating knob for causing the feed dog to make a drop feed. Numeral 63 is a manually operable knob for controlling the feed rate and reverse movement of the feed dog 54. Numeral 64 also denotes a manually operable knob for controlling the amplitude of the zigzag motion of the needle 32.

Numeral 65 is a loop retaining member having its intermediate portion rotatably mounted on the restraining member 49 by a stepped screw 66. The free end of the loop retaining member 65 constitutes a loop retaining section 67 for temporarily holding the released loop 51 pulled up through the opening 52 by the thread takeup mechanism. One side 67a of the loop retaining section 67 is so formed (FIG. 14) as not to project from one side 53a of the tongue 53 positioned on that part of the restraining member 49 to which there is pressed the recess 48 of the bobbin case with the rotation of the loop taker 41. Accordingly, the loop 51 released from the loop taker 41 is pulled up without being detained in a space between said one side 53a of the tongue 53 and recess 52. This enables good uniform chain stitches to be always formed without any ob struction and the loosening and consequential double formation of chain stitches.

Numeral 68 is a spring stretched across the other end of the loop retaining member 65 and the lug 70 of the later described fitting member 69. The spring 68 causes the loop retaining member 65 to rotate anticlockwise as shown in P16. 5, thereby normally keeping the retaining section 67 at a loop retaining position above the opening 52 so as to hold a loop released from the loop taker 41. Numeral 71 represents a groove formed at the upper part of the bobbin case retainer 47 across the recess 48 so as to extend toward both sides thereof The groove 71 has a sufliciently large size to receive the retaining section 67 of the loop retaining member 65. Above the groove 71 is disposed a projecting wall 72 for guiding the loop 51 released from the loop taker 41 onto the retaining section 67 so as to securely hold it thereon. The projecting wall 72 is so formed as to have its top positioned below that part of the bobbin case retainer 47 embracing both sides of the tongue 53 of the restraining member through which the needle 32 passes endwise. Accordingly, the loop released from the retaining section 67 is pulled up by the loop takeup mechanism without any obstruction and the slackening a consequential double formation of chain stitches. Coupled with the fact that one side 67a of the retaining section 67 is so fonned as not to project from one side 53a of the tongue 53, the aforementioned arrangement enables the needle thread to be fed smoothly and in consequence good chain stitches to be always formed. Accordingly, the device of the present invention is very useful, because there is no need for any machining of parts in practical application.

As seen from FIG. 3, the free end of the loop retaining member 65 is bent to surround the restraining member 49 so as to form a bent section 74 which contacts the underside of the restraining member 49 to prevent it from being lifted. Accordingly, when the retaining section 67 of the loop retaining member 65 lifts the bobbin case retainer 47 through the projecting wall 72, there is not applied any excess load to the race portion between the bobbin case retainer 47 and loop taker 41. This prevents the obstructed rotation of the loop taker 41 and the occurrence of noises and wear. Further, since the loop is securely retained by the loop retaining member 65, there can be efiected constant chain stitching.

Numeral 75 is an actuating plate pivoted to the restraining member 49 rotatably about a pin 76 fixed to the base end of said restraining member 49. The other end of the loop retaining member 65 engages the rising section 750 of said actuating plate 75 by the action of the spring 68, so that the free end 75b of the actuating plate 75 is normally urged upward so as to face the underside of the feed dog 54. The actuating plate 75 is swung downward with the descent of the feed dog 54 to cause the loop retaining member 65 to rotate against the action of the spring 68, thereby allowing the loop 51 retained by the loop retaining member 65 to be released by the thread takeup mechanism after the needle passes through the loop 51 next time.

As apparent from FIGS. 7, 9 and 10, a pivoting member 77 which supports the pin 76 of the actuating plate 75 so as to allow said actuating plate 75 to rotate in a space between the backside of the restraining member 49 and said pivoting plate 77, is fixed to the backside of the restraining member 49 by a pair of screws 79 passing through long slots 78 perforated in the fitting member 69 and restraining member 49. When the screws 79 are loosened to cause the pivoting member 77 to slide slightly along the long slots 78, then the pin 76 about which the actuating plate 75 is pivoted can be adjusted in position, thereby controlling the time at which the loop retaining member 65 is actuated by the feed dog 54. Accordingly, the operating time of the loop retaining member 65 is always set at a position adapted for chain stitching. To the suspended strip 93 of the restraining member 49 is pivoted a manually operable lever 94 for disengaging the throat plate by a stepped screw 95. One end 96 of the lever 94 so extends as to face the underside of that part of the throat plate where there is disposed an engaging elastic plate 87, and the other end of the lever 94 constitutes an operating knob 97. Numeral 98 represents a spring stretched across the throat plate disengaging lever 94 and restraining member 49. The spring 98 causes the lever 94 to rotate anticlockwise as shown in FIG. 6. According to the foregoing embodiment, there are fitted to the restraining member 49 all the loop retaining member 65, acmating plate 75 and throat plate disengaging lever 94, so that all these members may be put together as single unit, offering great advantage in assembling and manufacturing the subject device.

To the bracket arm 24 is pivoted a lever 99 rotatably about a fulcrum 100. At one end of the lever 99 is formed a thread seizing member 101 bent in the U-shape which cooperates with the thread takeup lever 33 in order to reduce the quantity of the needle thread released by said thread takeup lever 33. The thread seizing member 101 is located in a slot 1010 through which the thread takeup lever 33 passes and so formed as to embrace it. The thread seizing member 101 is normally kept in an inoperative position where it does not substantially reduce the quantity of the needle thread slackened by the thread takeup mechanism by means of a spring 102 stretched across the lever 99 and bracket arm 24 (H6. 21). The other end of the lever 99 is connected through a link 103 to an actuating lever 105 fitted to the cylindrical bed 22 by means of a pivot 104. The open end of the actuating lever 105 so extends as to face the underside of the first throat plate 80.

The second throat plate 90 is provided with an actuating projection 106 to press the other end of the actuating lever 105. Therefore when there is fitted the second throat plate 90 the actuating lever 105 is depressed by the actuating projection 106, causing the lever 99 to rotate about the fulcrum 100 with the descent of the link 103 and in consequence bringing the thread seizing member 101 from its inoperative position to that where it reduces the quantity of the needle thread as shown in FIG. 20. It will be noted that the first throat plate 80 is not provided with the actuating projection 106.

There will now be described the application of a chain stitching device according to the foregoing embodiment and the manner in which there is conducted chain stitching. FIGS. 3 to 6 show the condition in which the loop 51 released from the loop seizing beak 40 of the loop taker 41 is pulled up by the thread takeup mechanism and passes through the opening 52 between the tongue 53 and recess 48 to be retained by the retaining section 67 of the loop retaining member 65. At this time the feed dog 54 is in a rising position and disengaged from the actuating plate 75. The second throat plate 90 for chain stitching does not of course have a screw 89 as is the case with the first throat plate, so that when the feed dog 54 is brought down, the actuating plate 75 is in an inoperative position and the thread seizing section 101 is actuated by the actuating projection 106 of the second throat plate 90 to be brought to an operative position as shown in FIG. 20. When the work fabric 39 is carried forward one stitch pitch by the feed dog 54 and the needle 32 descends again into the loop 51 as shown in FIG. 16, then the feed dog 54 is brought downward and its underside engages the free end 75b of the actuating plate 75 to press said plate 75 downward for rotation. Accordingly, the rising section 750 of the actuating plate 75 actuates the other end of the loop retaining member 65 engaging said plate 75 to rotate the loop retaining member 65 against the action of the spring and release the loop 51 held by the retaining section 67.

As operation goes on, a fresh loop 51 formed by the fall of the needle 32 is seized by the loop seizing beak 40 of the loop taker 41 in preparation for the following chain stitching cycle. As shown in FIGS. 17 and 18, while the fresh loop 51 is being broadened by the loop taker 41, the preceding loop is pulled into the work fabric 39 to form a chain stitch. At this time, the thread takeup lever 33 descends to slacken the thread. However, since the thread seizing member 101 is positioned above the lever 33 when it is brought down, the thread is taken up by the thread seizing section 101 as shown in FIG. 20, so that the quantity of the needle thread to be supplied next time is reduced by that portion thus taken up. When the chain stitch is actually formed, the quantity of the needle thread becomes insufficient by that portion thus reduced as the loop is gradually broadened by the loop taker 41. Accordingly, the part of the preceding loop corresponding to said insufficient portion is pulled backward, causing the loop to be properly drawn into the work fabric 39 with the resultant formation of good chain stitches. Later when the feed dog 54 is lifted again, the loop retaining member 65 is brought back to its original position and the retaining section 67 is inserted into the groove 71 to be brought again to a position to retain the loop.

When, upon completion of desired chain stitching, it is desired to use a sewing machine for its original loclt' stitching, the cap member 25 of the cylindrical bed 22 is first opened and then the knob 97 of the manually operable lever 94 for disengaging the throat plate is depressed with the finger to cause the lever 94 to rotate against the action of the spring 98. Then the engaging elastic plate 87 of the second throat plate 90 is disengaged from the projection 86 by one end 96 of the lever 94, causing the second throat plate to be forcibly pushed out. After said second throat plate is taken out, there is fitted instead the previously provided first throat plate 80 for the original lock stitching. When the first throat plate 80 is to be fitted, it is first guided on to the stepped section 81 or a throat plate receiving seat of the cylindrical bed 22 and then the elastic plate 85 of said first throat plate 80 is pressed in for engagement with the underside of the peripheral portion of the opening for said plate so as to securely set it in place and that side of said plate 00 where there is disposed the engaging elastic plate 87 is pressed from above. Then the engaging elastic plate 87 registers with the projection 86, setting the first throat plate 80 in a prescribed place as shown in FIG. 15. At this time the screw 89 of the first throat plate engages the actuating plate 75 to press it for rotation from the position indicated by a two-dots dash line to that of a solid line, thus preventing its operation regardless of the movement of the feed dog 54. The loop retaining member 65 is operated in the same manner as in chain stitching, and brought to an inoperative position, quite independently of the loop passing through the opening 52 between the tongue 53 and recess 48 as shown in FIG. 16. Since the first throat plate 80 is not provided with an actuating projection 106, the actuating lever 105 is left free and the lever 99 is actuated by a spring 102 and the thread seizing member 101 is brought to an inoperative position shown in FIG. 21. At this time, the thread seizing member 101 is positioned below the lower dead point of the thread takeup lever 33 as illustrated, so that the quantity of the needle thread slackened by the thread takeup lever 33 is not substantially reduced. Therefore, when the shuttle thread is supplied to the case 46 there can be started ordinary lock stitching. When it is desired again to perform chain stitching, it is only required to fit the second throat plate in place of the first throat plate 80 in the same manner as in their interchange.

With the device according of the foregoing embodiment, the descent of the feed dog 54 due to operation of the knob 62 depresses the actuating plate 75 for rotation, bringing the loop retaining member 65 to an inoperative position. Accordingly, when there is conducted embroidering by lock stitching with the feed dog 54 depressed, there is no need to exchange the second throat plate 90 for the first throat plate 80, so that if it is desired alter chain stitching to carry out embroidering by lock stitching, it is not necessary to exchange these throat plates, but simply to operate the knob 62.

FIGS. 22 and 23 represent modifications of the thread seizing member 101. According to these modifications, the end of the lever 99 is fitted by a screw 107 with a thread seizing member 108 consisting of wire bent into a rectangular form. The thread is supplied from the stretching device 35 through the thread seizing member 108 to the thread takeup lever 33. With these modifications, when the thread seizing member 108 is in an operative position as shown in FIG. 23, the quantity of the needle thread slackened by the thread takeup lever 33 is decreased as in the aforementioned embodiment. When the thread seizing member is brought from its operative position down to its inoperative position, the thread is substantially left free from the action of the thread seizing member 108, and its quantity is not decreased. The thread seizing member 108 can be adjusted in position by loosening the screw 107.

As mentioned above, the present invention provides a lock stitch sewing machine equipped with a chain stitching device widely to broaden its application, thus offering great advantage to its general user.

What is claimed is:

1. A sewing machine including a frame having a bed with a work supporting surface,

a thread carrying eyed needle supported on the frame for endwise reciprocation,

a needle thread take-up mechanism mounted on the frame for alternately tightening and loosening the needle thread in timed relationship with the endwise reciprocation of the needle,

said bed having an opening formed with a throat plate receiving seat about said opening,

a loop taker assembly mounted in the bed below the throat plate receiving seat and circularly moved for seizure of thread loops formed by the reciprocation of the needle to form lock stitches,

a mechanism for linearly feeding a work fabric including a feed dog making the known four motions to advance the work fabric in a prescribed direction on the work supporting surface during each endwise reciprocation of the needle,

a movable loop retaining member positioned in the opening of the bed for temporarily retaining the loop which is being pulled up by the thread take-up mechanism following the release from the loop taker assembly,

an urging means connected to the loop retaining member for normally setting the loop retaining member in a position to retain the loop released from the loop taker assembly, and

an actuating member provided between the loop retaining member, and the feed dog and having a first portion operatively connected with the loop retaining member, a second portion disposed adjacent the opening of the bed and a third portion normally urged toward the lower end of the feed dog, 7

said actuating member being adapted to move the loop retaining member against the action of the urging means by the downward movement of the feed dog, thereby causing the loop retained by the loop retaining member to be released therefrom after the needle passes through the loop in the next downward movement, said second portion of said actuating member being adapted to be engaged by an actuating means on the bottom of a throat plate to thereby hold the loop retaining member in the released position for lock stitching.

2. A sewing machine according to claim 1 including a throat plate formed with an actuating means on the underside thereof engaging the second portion of the actuating member thereby disengaging the actuating member from the feed dog and setting the loop retaining member in non-operable condition.

3. A sewing machine according to claim 1 including a throat plate and a thread quantity adjusting means, said thread quantity adjusting means being provided for reducing the quantity of the needle thread slackened by the thread take-up mechanism in co-operation therewith, said thread quantity adjusting means including an actuatable member adjacent said opening in said bed, and an actuating projection formed on the underside of said throat plate cooperating with said actuatable member for bringing the thread quantity adjusting means in an operable position so as to reduce the quantity of the needle thread.

4. A sewing machine according to claim 3 wherein said thread take-up mechanism includes a reciprocable thread take-up lever, and said thread quantity adjusting member is bent in U-shaped to pass the take-up lever therein.

5 A sewing machine according to claim 1 wherein said feeding mechanism includes means for causing the feed dog to remain in its lowered position and an operating knob for the same, thereby the loop retaining member is brought in arresting condition not to retain the loop released from the loop taker assembly through the actuating member when the operating knob is operated.

6. A sewing machine including a frame having a bed with a work supporting surface,

a thread carrying eyed needle supported on the frame for endwise reciprocation,

a needle thread take-up mechanism mounted on the frame for alternately tightening and loosening the needle thread in time relationship with the endwise reciprocation of the needle,

a throat plate removably mounted on the throat plate receiving seat about said opening to close the opening of the bed, and perforated with a needle aperture adapted for chain stitching,

a loop taker mounted in the bed below the throat plate and rotated about an axis for seizure of thread loops formed by the reciprocation of the needle to form lock stitches, a bobbin case retainer journaled in the loop taker and adapted to accomodate an ordinary bobbin case therein,

a restraining member fixed in the bed below the throat plate for preventing the bobbin case retainer from rotating with the loop taker,

a mechanism for linearly feeding a work fabric including a feed dog making the known four motions to advance the work fabric in a predetermined direction during each endwise reciprocation of the needle,

a loop retaining member rotatbly supported on the restraining member to temporarily retain the loop which is being pulled up by the thread take-up mechanism following the release from the loop taker at one of its end,

spring means stretched between the loop retaining member and the restraining member for imparting a'rotating force to the loop retaining member to normally keep it in a position to retain the loop released from the loop taker,

an actuating plate having a base end swingably supported by the restrain member, an intermediate portion disposed adjacent the opening of the bed and a free end normally urged toward the lower end of the feed dog by the engagement of the other end of the loop retaining member to which a rotating force is imparted by the spring means,

said actuating plate being adapted to swing downward by the downward movement of the feed dog to rotate the loop retaining member against the action of the spring means, thereby causing the loop retained by the loop retaining memberto be released therefrom after the needle passes through the loop in the next downward movement.

7. A sewing machine according to claim 6 wherein the restrainingmember is further fitted with a manually operable lever for forcibly removing a throat plate to be fitted to the throat plate receiving seat.

i F l

Claims

1. A sewing machine including a frame having a bed with a work supporting surface, a thread carrying eyed needle supported on the frame for endwise reciprocation, a needle thread take-up mechanism mounted on the frame for alternately tightening and loosening the needle thread in timed relationship with the endwise reciprocation of the needle, said bed having an opening formed with a throat plate receiving seat about said opening, a loop taker assembly mounted in the bed below the throat plate receiving seat and circularly moved for seizure of thread loops formed by the reciprocation of the needle to form lock stitches, a mechanism for linearly feeding a work fabric including a feed dog making the known four motions to advance the work fabric in a prescribed direction on the work supporting surface during each endwise reciprocation of the needle, a movable loop retaining member positioned in the opening of the bed for temporarily retaining the loop which is being pulled up by the thread take-up mechanism following the release from the loop taker assembly, an urging means connected to the loop retaining member for normally setting the loop retaining member in a position to retain the loop released from the loop taker assembly, and an actuating member provided between the loop retaining member, and the feed dog and having a first portion operatively connected with the loop retaining member, a second portion disposed adjacent the opening of the bed and a third portion normally urged toward the lower end of the feed dog, said actuating member being adapted to move the loop retaining member against the action of the urging means by the downward movement of the feed dog, thereby causing the loop retained by the loop retaining member to be released therefrom after the needle passes through the loop in the next downward movement, said second portion of said actuating member being adapted to be engaged by an actuating means on the bottom of a throat plate to thereby hold the loop retaining member in the released position for lock stitching.

5. A sewing machine according to claim 1 wherein said feeding mechanism includes means for causing the feed dog to remain in its lowered position and an operating knob for the same, thereby the loop retaining member is brought in arresting condition not to retain the loop released from the loop taker assembly through the actuating member when the operating knob is operated.

6. A sewing machine including a frame having a bed with a work supporting surface, a thread carrying eyed needle supported on the frame for endwise reciprocation, a needle thread take-up mechanism mounted on the frame for alternately tightening and loosening the needle thread in time relationship with the endwise reciprocation of the needle, said bed having an opening formed with a throat plate receiving seat about said opening, a throat plate removably mounted on the throat plate receiving seat about said opening to close the opening of the bed, and perforated with a needle aperture adapted for chain stitching, a loop taker mounted in the bed below the throat plate and rotated about an axis for seizure of thread loops formed by the reciprocation of the needle to form lock stitches, a bobbin case retainer journaled in the loop taker and adapted to accomodate an ordinary bobbin case therein, a restraining member fixed in the bed below the throat plate for preventing the bobbin case retainer from rotating with the loop taker, a mechanism for linearly feeding a work fabric including a feed dog making the known four motions to advance the work fabric in a predetermined direction during each endwise reciprocation of the needle, a loop retaining member rotatbly supported on the restraining member to temporarily retain the loop which is being pulled up by the thread take-up mechanism following the release from the loop taker at one of its end, spring means stretched between the loop retaining member and the restraining member for imparting a rotating force to the loop retaining member to normally keep it in a position to retain the loop released from the loop taker, an actuating plate having a base end swingably supported by the restrain member, an intermediate portion disposed adjacent the opening of the bed and a free end normally urged toward the lower end of the feed dog by the engagement of the other end of the loop retaining member to which a rotating force is imparted by the spring means, said actuating plate being adapted to swing downward by the downward movement of the feed dog to rotate the loop retaining member against the action of the spring means, thereby causing the loop retained by the loop retaining member to be released therefrom after the needle passes through the loop in the next downward movement.

7. A sewing machine according to claim 6 wherein the restraining member is further fitted with a manually operable lever for forcibly removing a throat plate to be fitted to the throat plate receiving seat.