US3625169A

US3625169A - Chain-stitch-forming device for lock-stitch sewing machines

Info

Publication number: US3625169A
Application number: US867721A
Authority: US
Inventors: Chikao Yamashita; Koji Nishiyama
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1969-09-01
Filing date: 1969-10-20
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07
Also published as: CH514716A

Abstract

A chain-stitch-forming member is fitted into the loop of a lockstitch sewing machine in place of the usual bobbin case. The chain-stitch-forming insert member has a loop retaining projection for retaining a loop in cooperation with a needle of the machine and a cam mechanism between the loop taker and the projection to effect the prescribed movement of the projection to form chain-stitches as the machine operates.

Description

United States Patent Chikao Yamashita Aichi-ken;

Koji Nishiyama, Osaka-shi, both of Japan 867,72 1

Oct. 20, 1969 Dec. 7, 1971 Brothers Kogyo Kabushiki Kaisha Mizuho-ku, Nagoya-shi, Japan [72] Inventors [21 App]. No. [22] Filed [45 Patented [73 Assignee [32] Priorities Sept. 1, 1969 [33] Japan Mar. 5, 1969, Japan, No. 44/ 16671; Oct. 21, 1968, Japan, No. 43/766611 [54] CIIAIN-STITCH-FORMING DEVICE FOR LOCK- STITCH SEWING MACHINES 13 Claims, 18 Drawing Figs.

[52] U.S.Cl 112/168,

51 1111.0 005111/14 50 FieldoiSearch 112/168, 199,201,232,181,183

[56] References Cited UNITED STATES PATENTS 727,053 5/1903 Anthony 112/168 3,173,390 3/1965 Bartosz 112/168 3,173,391 3/1965 Doerner 112/168 3,253,560 5/1966 Ketterer et a1. 112/168 3,447,498 6/1969 Eguchi 112/168 X Primary ExaminerH. Hampton Hunter Anorney-F1ynn & Frishauf ABSTRACT: A chain-stitch-forming member is fitted into the loop of a lock-stitch sewing machine in place of the usual bobbin case The chain-stitch-forming insert member has a loop retaining projection for retaining a loop in cooperation with a needle of the machine and a cam mechanism between the loop taker and the projection to effect the prescribed movement of the projection to form chain-stitches as the machine operates.

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PATENTEDDEB (I971 3.625169 sum user 12 FIG. 3

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PATENTEU DEE 7197i sum 120i 12 CIIAIN-S'IITCI-I-FORMING DEVICE FOR LOCK-STITCH SEWING MACHINES The present invention relates to sewing machines and more particularly to devices for converting a lock stitch sewing machine into a chain stitch sewing machine.

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. While, to meet this demand, there have been employed various types of chain stitch device, they are of complicated arrangement and fail to be easily fitted into the sewing machine.

With respect to the ordinary sewing machine having lock stitch forming instrumentalities with a loop taker for performing lock stitches in cooperation with a needle, the present invention consists in fitting a chain stitch forming member into the loop taker in place of the ordinary bobbin case so as to permit always chain stitching of very good conditions. According to the present invention, the chain stitch forming member has the same shape and size and can be detachably fitted into the loop taker in the same manner as the ordinary bobbin case, so that interchange of the bobbin case for said chain stitch forming member or vice versa is very simple. Moreover, a sewing machine according to the present invention has exactly the same arrangement as the ordinary lock stitch type, except for said chain stitch forming, member, thus offering great advantage in construction.

This invention can be more fully understood from the following detailed description when taken in connection 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 stitch forming device according to the invention, wherein a frame is shown by two dot-dash lines and which includes a loop taker swingable around a horizontal axis extending parallel with a direction of feeding of a work fabric;

FIGS. 2 to 7 jointly present a chain stitch forming device for fitting the sewing machine shown in FIG. 1, according to an embodiment of the invention; FIG. 2 is an elevation of an entire chain stitch forming device where a thread loop released from a loop taker is retainedby a loop retaining projection extended upwardly; FIG. 3' is a sectional view on line 3-3 of the chain stitch forming device of FIG. 2; FIG. 4 is a similar sectional view on line 3-3 of said device as taken from the opposite side of the device to that shown in FIG. 3 where the loop retaining projection is inclined in such direction as allows it to be removed from the released loop; FIG. 5 is a plan view, with part broken away, of the device of FIG. 2 as taken from line 5-5 thereof; FIG. 6 shows the perspective views of the constituent parts of the device of FIG. 2; and FIG. 7 is a perspective view of a modification of the bridge member of the device of FIG. 2;

FIGS. 8 to 11 jointly show a chain stitch forming device according to another embodiment of the invention, said device being adapted for use in a lock stitch sewing machine wherein there is disposed a loop taker swingable around the horizontal axis normal to the direction in which the work fabric travels; FIG. 8 is a side view of said chain stitch device where there is retained by a loop retaining projection a thread loop released from the loop taker; FIG. 9 is a sectional view on line 99 of the device of FIG. 8; FIG. 10 is a side view of said device similar to that of FIG. 8 where there is retained by the loop seizing beak of the loop taker a loop freshly formed by a result of the endwise reciprocation of the needle and FIG. 11 is a sectional view on line 11-11 of the device of FIG. 10;

FIGS. 12 to 18 jointly illustrate a chain stitch forming device according toa third embodiment of the invention, which includes a loop taker rotatable around a horizontal axis extending parallel with a direction of feeding of a work fabric. FIG. 12 is an elevation of said device where there is retained a loop released from the loop taker by the upwardly truned loop retaining projection of a chain stitch forming member of said device; FIG. 13 is a sectional view on line l3-13 of the device of FIG. 12; FIG. 14 is a plan view of the device of FIG. 12 as taken from line 1414; FIG. 15 is a sectional view of the device similar to that of FIG. 13 where there is released the loop; FIG. 16 is a sectional view of a chain stitch forming member as taken from line 16-l6 of the device of FIG. 13; FIG. 17 is a sectional view of said member of FIG. 16 as taken from line 17-17 thereof; and FIG. 18 gives the perspective views of the dismembered parts of the member of FIG. 16.

A sewing machine shown in FIG. 1 is an ordinary lock stitch type, a machine frame 20 including a bed 21 from which rises a standard 22 supporting a bracket arm 23 overhanging the bed. A main shaft 24 journaled lengthwise in the bracket arm 23 drives all of the moving parts of the sewing machine and may be actuated by an electric motor (not shown), by a foot treadle or the like. A counterbalanced crank 25 on the main shaft 24 is operatively connected by means of a connecting rod 26 to a needle bar 27 endwise slidable in a support 28 pivotally secured as at 29 in the bracket arm and carrying at its lower extremity an eye-pointed needle 30. A needle thread takeup lever 31 is also actuated by said crank 25 and constrained by an anchor link 32 so as to draw tight and slacken the needle thread in timed relation with the endwise reciprocation of said needle 30. The path of the needle thread passes from a supply (not shown) to a thread tension device 33 through an eyelet 34 in the takeup lever 31, and then through appropriate guides such as the thread guide 35 on the needle bar 27 and to the needle eye. This needle thread control arrangement is typical of that which is required for lock stitch formation.

Below that part of the underside of the bed 21 which is disposed right under the needle 30 is provided a stitch forming or loop taker assembly 36 for carrying out a sewing operation cooperated with said needle as shown in FIGS. 2 to 7. Reference 37 is a loop taker housing secured to the frame in which an internal circular raceway 39 is defined by a cover ring 38 consisting of the part of said housing and the inner surface thereof. In the raceway 39 is formed a discontinuous peripheral bearing rib 40 and removably attached a loop taker 42 having a loop seizing beak 41 at its end portion in which a ordinary bobbin case 43 may be accommodated. The bobbin case is prevented from swinging with the loop taker by a recess 44 of said cover ring 38 as well known. Under the bed is provided a loop taker shaft 46 at the end of which is secured a driver 45 which causes the loop taker 42 to swing around the horizontal axis thereof. Under the bed also is mounted a swing shaft 49 which is rotated by a crank rod 48 connected to a crank portion 47 of said main shaft 24, the shaft 49 driving the loop taker shaft 46 through a set of bevel gears 50, 51. Consequently, the needle 30 and loop taker 42 are driven in time relation to seize a loop of a thread 52 carried on the eye of the needle 30 by the loop taker 42 during stroke of the needle 30 downwardly through a needle aperture 53 of a needle plate 54 supported by said bed 21 and the release of said seized loop from the loop taker 42 during the succeeding upward stroke of the needle 30 in this embodiment, the loop taker 42 oscillates back and forth in a rotary movement as customary in the art.

A conventional feed dog 56 is provided under the bed, which carries out a known feed motion or moving into and out of the slot 55 of the needle plate 54 and advances a work fabric 93 on the work support in one direction from said needle aperture 53 between each needle penetration thereof. The feed dog 56 is secured to a feed bar 58 connected with a feed advancing shaft 57 which is swung by a forked rod 60 having two forked end portions between which a feed cam 59 on the main shaft 24 is held, thereby applying feed advance and return movements to the feed dog 56. At the one end of the shaft 63 of a forked arm 62 connected to a feed lift eccentric 61 on said rock shaft 49 is provided an operable arm 64 operably connected to said shaft 57, the feed dog 56 being applied up and down movements by the rotation of the eccentric 61.

It will be appreciated that as it is conventional in the art the linear work-feeding mechanism is timed relatively to the needle reciprocation so that the feed dog 56 is lifted and advanced while the needle 30 is raised out of any work on the needle plate 54, and the feed dog 56 is lowered beneath the needle plates 54 and returned while the needle descends.

The chain stitch forming device of the present invention will be described with reference to FIGS. 2-7. A chain stitch adapter member 67 is placed into the loop taker 42 of assembly 36, rather than a bobbin case 43 and thread spool. At the center of the inner bottom surface of the loop taker 42 is a projecting bobbin supporting pin 66 (FIG. 3) having an annular groove 65 formed about the outer end portion. The chain stitch member 67 comprises a forward plate like member 68 made of a metal plate, at the upper end of which is disposed an upwardly extending loop retaining projection 69 and a rear member 71 of plastics material secured to the forward member 68 by screws 70. The part of said rear member 71 is formed as a contact element 74 which is engageable by the inner edge of the curved overhanging lip 73 of front wall 72 of the loop taker 42; the lip portion 73 functions as a cam member; its distance from the center of rotation of loop taker 42 is variable, as seen in exaggerated form in FIGS. 8 and 10. That portion 75 of the forward member 68 which lies near its projection 69 freely engages with recess 44 of the cover ring 38, preventing the chain stitch forming member 47, like the bobbin case of the ordinary sewing machine, from being unduly rotated. At the center of the member 67 is formed a hole 76 elongated in the vertical direction and having a prescribed width. The inner surface of the upper surface of the upper end 77 of the hole is inclined as seen in FIG. 3 for the undermentioned purpose. Bobbin supporting pin 66 is inserted into hole 76; since the hole is elongated, the chain stitch member 67 can reciprocate vertically. Numeral 78 represents a substantially L-shaped stop lever adapted to engage in groove 65 of pin 66. It is interposed between the forward and

rear members

68 and 71, whose intermediate portion is rotatably pivoted by a pivot 79 projectingly formed on said rear member 71. One end 80 of said lever 78 is so disposed as to face the annular groove 65 of the bobbin-supporting pin 66. Numeral 81 denotes a first spring stretched between the aforementioned end 80 of the lever 78 and the rear member 71. This spring 81 urges said end 80 into the annular groove 65 of the bobbin-supporting pin 66 for engagement therewith, thereby preventing the chain stitch forming member 67 from coming off the loop taker 42 and also urging said member 67 upward so as to allow the contact member 74 to be tightly attached to the curved overhanging lip 73 of the loop taker 42. A handgrip plate 82 is fitted to the front side of the forward member by a pin 83 swingably supported in the forward member 68. An extension arm 85 is engageable with the other end 84 of the L-shaped lever 78 and another arm 87is engaged by a second spring 86. The grip plate 82 is normally depressed by the action of the second spring 86. When the grip plate 82 is raised against the force of

springs

81 and 86, the arm member 85 engages with the other end 84 of the L-shaped lever 78 and rotates it to remove end 80 thereof from the annular groove 65 of the bobbin-supporting pin 66. Numeral 88 (FIG. 7) denotes a bridge member fixed to the loop taker housing 37 and numeral 89 (FIG. 2; FIG. a stationary thread guide formed on said bridge member 88. This guide 89 engages with the loop retaining projection 69 of the adapter 67 to allow the loop 52 released from the loop taker 42 to be temporarily retained by said projection 69, thereby obstructing the passage of the loop 52. The guide 89 is placed to be lower than the upper point reached by the loop retaining projection 69 for temporarily holding the loop of the thread 52 released from said loop taker 42 on projection 69. It prevents slipping out of the loop thread 52 by engagement with the projection 69. The curved overhanging lip 73 of the loop taker moves the adapter 67 downwardly by engagement with contact element 74, thus constituting a cam means and lowers the top of said projection 69 below the level of said stationary thread guide 89 according to said oscillating movement of said loop taker 42 to permit formation of the loop bythread 52 entrapped on said projection by the needle thread takeup mechanism after the needle upon being next lowered, has been passed through said loop. Numeral is a loop-restricting portion formed on the bridge member 88 in a manner to extend ahead of the loop retaining projection 48. When the loop released from the loop taker 42 is temporarily retained by the loop retaining projection 69, said loop-restricting portion 90 prevents said loop 52, due to the lifting action of a thread take up mechanism, from slipping over the upper surface of the loop-retaining projection 69 and getting through the gap between said projection and stationary thread guide 89.

To employ the chain stitch forming device of the present in vention in an ordinary lock stitch sewing machine of FIG. 1, the bobbin case is removed and the chain stitch member 67 is fitted instead into the loop taker 42. The grip plate 82 is raised against the force of

springs

81, 86 and the adapter 67 will then snap in place similar to the bobbin case.

Operation and formation of chain stitches: FIGS. 2 and 3 present the condition where the loop 52 released from the loop taker 42 is lifted by the thread takeup mechanism of FIG. 1, passes between the portion 75 of the forward member 68 lying near the projection 69 and the recess 44 of the loop taker 42 and is brought to rest at the upper part of the projection 69 by the stationary thread guide 89. At this time, the loop tends, due to the lifting action of the thread takeup mechanism, to slip over the upper surface of the projection 69 and get through the gap between said projection 69 and guide 89 (this tendency becomes particularly prominent as the machine operation is more accelerated). However, the loop restriction portion 90 formed on the bridge member 88 obstructs the loop in slipping over the upper surface of the projection 69, thus preventing the omission of stitches.

After the aforementioned condition is realized, the work fabric 93 is made to feed by the work-feeding mechanism for a distance equivalent to one stitch pitch. The needle 30 is brought down into the loop 52 allowing the curved overhanging lip 73 of the loop taker 42 to engage with the contact member 74. As a result of the rotary movement of loop taker 42, camming portion 73 engages member 74, and the chain stitch forming member 67 is urged downward against the force of the first spring 81 therein. This downward urging is continued until the loop-retaining projection 69 disengages from the stationary threaded guide 89; movement of the adapter member 67 is guided by the elongated hole 76 engaging with the bobbin supporting pin 66. Upon disengagement of projection 69 from guide 89, the loop 52 retained by said loop retaining projection 69 'is released. After the loop 52 is released, the rear part of the upper end 77 of the elongated hole 76 engages with the bobbin supporting pin 66, so that the downward movement of the chain stitch forming member 67 is stopped. Rotation of the loop taker 42 however, continues, and the contact member 74 continues to be engaged by the curved overhanging camming lip 73 of the loop taker 42. As shown in FIG. 4, therefore the loop-retaining projection 69 of the chain stitch forming member 67 is inclined outwardly, that is, away from guide 89 and restricted portion 90, thus separating from the released loop 52. The inclined portion 77 on the inner surface of the upper end of the elongated hole 76 permits this tilting movement of member 67.

As the sewing machine keeps on running, a loop freshly formed by the downward needle 30 is seized by the loop taker 42 in preparation for the following stitch forming operation. At this time, and upon reverse rotary movement of loop taker 42 and with it, camming lip 73, the loop-retaining projection 69 of the chain stitch member 47 is returned from its inclined position conversely to the aforesaid case, allowing said member 67 to be lifted to its original level. Accordingly, when the loop retaining projection 69 is raised again, it is prevented from again seizing the released loop, causing no double stitches and permitting good stitching at all times.

As shown in FIG. 7, a top portion 91 engaging with the upper end surface of the loop retaining projection 69 when it is lifted may be arranged on bridge member 88. Guide 89 and loop restricting portion 90 are formed into a rectangular inverted C shape or channel in cross section and surrounding projection 69, thereby defining a groove 92. According to this arrangement, when the loop 52 released from the loop taker 42 is temporarily retained by the loop-retaining projection 69, the major part of the loop 52 is prevented by the loop-restricting portion 90 from passing over the upper end surface of said projection 69. Even then the loop 52 tends to pass between said projection 69 and groove 92 and slip over the upper end surface of said projection 69. However, the top portion 91 of the aforesaid rectangular C shaped section fully retains the loop 52, and reliably prevents skipping of stitches. Manufacture of the stationary thread guide 89 and loop-restricting portion 90 together with top portion 91 and the bridge member 88 is easily and cheaply accomplished.

Embodiment of FIGS. 8 to 11: the chain stitch forming device is adapted for use in a lock stitch sewing machine wherein the loop taker assembly (consisting of a loop taker housing, loop taker and bobbin case retainer) is rotatable about a horizontal axis arranged perpendicularly to the direction in which a work fabric travels over a needle plate. The same parts of this embodiment as those of the preceding one are denoted by the same numerals and description thereof is omitted. A chain stitch forming member 100 is fitted to a bobbin supporting pin 66 (FIGS. 8 and 9) projecting at the center of the inner bottom surface of the loop taker 42. About the outermost end of said pin 66 is formed an annular groove 65. The chain stitch member 100 is supported by pin 66 in a manner to move vertically through a vertically elongated hole 101 and another elongated hole 102 having the same length as the former 101 perforated by punching. Member 100 is prevented from moving inward by an embossed part 103 formed thereon so as to engage with the outermost end of the supporting pin 66. An upwardly extending loop retaining portion 104 is formed on member 100. Member 100 is further formed with a contact strip 105 closely attached under pressure to the inside of the curved overhanging lip 73 of the loop taker 42 which constitutes a cam member functioning as in the preceding embodiment. The intermediate part 106 located at the base of said loop-retaining projection 104 prevents, jointly with the recess 44 of the cover ring 38, the chain stitch forming member 100 from being unduly rotated, as is the case with the preceding embodiment and an ordinary bobbin case. The loop retaining projection 104 is formed to have a wide width in an opposite direction to the projection of the preceding embodiment, namely, in a direction perpendicular to that in which a work fabric 93 travels. The chain stitch forming member 100 has a stop lever 108 rotatably supported by a pivot 107, the middle part essentially of said lever extending in a direction to face the annular groove 65 of the pin 66. A spring 109 is stretched between the other end of lever 108 and one side of the stitch forming member 100. Spring 109 causes the lever 104 to be fitted into the annular groove 65 so as to prevent said lever 108 from coming off the loop taker 42 of the chain stitch forming member 100 and urges member 100 upward to allow the contact strip 105 to be pressed to the curved overhanging lip 73 of the loop taker 42. A hand-operable lever 110 extends to the opposite side of the pivot 107 as an extension of the stop lever 108 in order to remove the stop lever 108 from the annular groove 65. A stationary thread guide 11] is fonned at the underside of the needle plate 54. Stationary thread guide 11] engages with the loop-retaining projection 104 so as to allow the loop 52 released from the loop-seizing beak 41 of the loop taker 42 to be temporarily retained by the loop-retaining projection 104, thereby preventing the loop 52 from passing over projection 104.

A depression 112 is formed at that part of the needle plate which is located around the needle eye when it is brought down, so as to ensure the smooth run of the loop 52, when the thread is tightened. A strip 113 is formed on the stop lever [08, which engages with the upper surface of the bobbin-supporting pin so as to prevent the chain stitch forming member 100 from falling inwardly.

Operation: Essentially, the operation is similar to that previously described. When a work fabric 93 is moved forward for a distance equivalent to one stitch pitch and the needle 30 is brought down again to the loop 52, the return rotation of the loop taker 42 causes the curved overhanging camming lip 73 of said loop taker 42 to engage with the contact strip 105, thereby urging the chain stitch forming member downward against the action of the spring 109. Downward urging is continued, the stitch forming member 100 is guided by the

elongated holes

101 and 102 engaging with the supporting pin 66, until the loop-retaining projection 104 is brought to a position where it is disengaged from the stationary thread guide 1 l 1. At this time the loop 52 retained by said projection 104 is released. Before it is urged downward to a position where it is disengaged from the guide 111, the loop-retaining projection 104 is pressed to the guide 111 under the action of the curved overhanging lip 73 of the loop taker 42 as a result of the return rotation of said loop taker 42.

FIGS. 10 and 11 show the condition where, upon completion of a return oscillation, the loop taker 42 made a forward rotation and the loop seizing beak 41 took up a loop freshly formed by the descending needle 30. The chain stitch forming member 100 is inclined in such a direction as to allow the loop-retaining projection 104 to be removed from the released loop 52 under the action of the curved overhanging lip 73 of the loop taker 42, namely, in a direction in which said member 100 is carried away from the needle 30. Since the lip 73 of the loop taker 42 frictionally contacts the contact strip 105, the inclination of the chain stitch forming member 100 is caused by the forward rotation of said loop taker 42 in the same direction as the rotation. Of course, this inclination is carried out insofar as the intermediate portion 106 of the loop retaining projection 104 is allowed to move crosswise in the recess 44. As the sewing machine further keeps on running, the chain stitch forming member 100 is lifted conversely to the just preceding operation and brought back from the aforesaid inclined position.

in the second embodiment of the present invention, the stationary thread guide was formed on the underside of the needle plate, but the recess of the loop taker may be used as it is to serve as such stationary thread guide. However, the provision of a separate stop member is preferred to obtain tight stitches and in order to bring the needle reliably into the loop.

Like the preceding embodiment, that of FIGS. 8 and 11 offers great convenience, because chain stitches can bemade simply by fitting a chain stitch forming member into a loop taker assembly in place of the bobbin case of the ordinary lock stitch sewing machine. Double stitches are prevented and good chain stitches are formed. in addition, this embodiment is of simpler arrangement than the first embodiment, because a single spring serves the double purpose of allowing the stop lever to be fitted into the annular groove of the bobbin supporting pin to prevent this lever from coming off the loop taker and urging the chain stitch member upward so as to cause the contact strip thereof to be pressed to the curved overhanging lip of the loop taker.

Embodiment of FIGS. 12 to 18: The same parts, particularly those associated with the loop takeup assembly, of this third embodiment as those of the preceding embodiments are denoted by the same numerals and description thereof is omitted.

A machine frame supports the rotary loop taker shaft of a loop taker assembly which can fully rotate about the central axis of said assembly. A loop taker 121 is fitted to the end of shaft 120. A bobbin case retainer 122 containing a detachably fitted bobbin case of the known type is slidably retained in loop taker 121 which is so designed as to make two full rotations during endwise reciprocation of the needle 30. A recess 123 is formed at that part of the peripheral wall of the retainer 122 which is located near the point of needle penetration. A restraining member 124 for the bobbin case retainer 122 is fitted to the machine frame, one end of said member 124 being fixed by screws 125' (FIG. 14). The upper end of restraining member 124 is formed with a projection 125 freely engaging with the aforesaid recess 123 thereby allowing the bobbin case retainer 122 to be brought to rest. In this embodiment, similar to the other embodiments, the loop taker 121 and needle 30 are driven in timed relationship with each other. A cylindrical case 128 is used in place of an ordinary bobbin case, at the central part of which there is projectingly disposed a short tube 129 for receiving the bobbin-supporting pin 126 projectingly provided at the central part of the inner bottom surface of the retainer 122 and having an annular groove 127 at the top part. Cylindrical case 128 has a grip plate 130 (FIG. 12) for allowing it to be detachably fitted into the retainer 122 and has substantially the same shape and size as an ordinary bobbin case. The case has a projection 132 fitted in a recess 131 of said bobbin case retainer 122. The short tube 129of the cylindrical case 128 is inserted into a guide plate 133 (FIG. 18), which is securely set in place within the cylindrical case 128 by a coil spring 134 and stop ring 135..

A loop holder 136, perforated with a vertically elongated hole 137, is introduced over the short tube 129, and placed to move vertically through the space defined by the guide plate 133 and the mutually facing folded portions 138 formed on both sides of said guide plate 133. The upper end of the loop holder 136 is notched to form a notch portion 140. The final projecting end forms a contact member 141, extending through the folded portions 138 formed in the guide plate 133 and those formed in the loop taker, and an upward projection 142 holding the loop. A notch 143 is formed on the bottom wall of the recess 123 so as to allow the projection 142, together with the cylinder case 128 to be detachably fitted into the retainer 122. A spring 144 is stretched between the guide plate 133 and loop holder 136 so as to urge the loopretaining projection 142 upward at all times. The aforementioned members denoted by numerals 128 to 144 constitute a chain stitch member to be detachably fitted into a loop takeup assembly. A stationary thread guide 145 open at one end, is formed on the projection 125 of the restraining member 124 (FIG. 15). Guide 145 engages the end of the upward projection holding the loop by the action of the spring 144, thereby allowing the loop, when released from the loop-seizing beak 146 of loop taker 121 to be retained by projection 142. A cam portion 147 is formed in the loop taker 121 so as to engage with the contact member 141 of the loop holder 136 when the needle is brought down into a loop retained by the upward projection 142, thereby allowing the loop holder 136 to be brought down against the force of the spring 144 to release a loop from the loop retaining upward projection 142.

Operation: FIGS. 12 to 14 show the condition where the loop 52 released from the loop-seizing beak 146 of the loop taker 121 is lifted by a threaded takeup mechanism (not shown) and retained by the loop retaining upward projection 142 in cooperation with the guide 145 formed on the projection 125 of the restraining member 124. After the aforesaid condition is reached, a work fabric 93 is fed by one stitch pitch. When the needle is brought down again into the loop 52 the cam portion 147 (FIG. 15) formed on the loop taker 121 engages with the contact member 141, as a result of the rotation of the loop taker 121, and urges loop holder 136 downward against the action of the spring 144, thereby releasing the loop 52 retained by the loop-retaining upward projection 142. As the sewing machine further keeps on running, the loop-seizing beak 146 of the loop taker catches a loop, freshly formed by the downcoming needle 30, in preparation for the formation of the following chain stitch. At this time the contact member 141 is disengaged from the cam portion 147 to allow the loop retaining member 136 to be lifted again by the action of the spring 144 and brought to a state ready to seize the loop 52 released from the loop taker.

In this third embodiment, the loop holder 136 is arranged to move with respect to the stationary cylinder case 128. However, the chain stitch member may be so arranged as to permit these members to move as an assembly.

As in the first and second embodiments, the chain stitch device of the third embodiment is of simple arrangement and can be detachably fitted with ease into an ordinary lock stitch sewing machine. The device of the third embodiment particularly is simple in arrangement, so that it can be easily manufactured at low cost.

What we claim is:

1. A chain stitch forming device for a lock stitch sewing machine, said machine including a frame having a work support formed with a needle aperture;

a thread-carrying eyed needle disposed above the work support for endwise reciprocation through said needle aperture;

a needle thread takeup mechanism mounted on said frame for alternately tightening and loosening said needle thread in timed relationship with the endwise reciprocation of said needle;

a loop taker disposed on said frame for circularly moving about the axis of the loop taker assembly, said loop taker being formed with a bobbin-receiving cavity to accommodate a bobbin;

stop means for preventing the bobbin from making circular movement together with said loop taker,

means for driving said needle and loop taker in timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of the needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker;

and a linear work-feeding mechanism for advancing said work fabric carried on its support in a prescribed direction from said needle aperture during each endwise reciprocation of said needle;

wherein said chain stitch forming device comprises a body member formed to be fitted into the cavity of said loop taker in replacement of a bobbin;

an upwardly projecting loop-retaining member disposed on said body member on the work-feeding side close to the point of needle penetration;

means connected to said loop-retaining member to urge it upwardly;

a stationary thread guide interposed between said loopretaining member and said point of needle penetration positioned at a point lower than the maximum height attained by the top of said loop-retaining member to temporarily retain the loop released from the loop taker on said loop-retaining member by cooperation of said thread guide and said loop-retaining member; and

cam means located between said loop taker and said loopretaining member operating in synchronism with the needle and engaging said loop retaining member to move the top of said loop-retaining member down to below the level of said stationary thread guide as a result of the circular movement of said loop taker and to allow the loop retained on said loop-retaining member to be taken off therefrom by said thread takeup mechanism after said needle, upon being brought down during a subsequent stitch-forming movement passes through said loop, thereby forming chain stitches with threads carried by said needle.

2. The chain stitch forming device for a lock stitch sewing machine according to claim 1 further comprising means for moving said top of said loop-retaining member by the action of said cam means in such direction as to remove said top from said released loop after said top is brought down to below the level of said stationary thread guide.

3. The chain stitch forming device for a lock stitch sewing machine according to claim 1 wherein said stationary thread guide is positioned on the underside of said work support formed with said needle aperture.

4. The chain stitch fonning device for a lock stitch sewing machine according to claim I wherein said body member is formed t'o'fit the bobbin cavity and is of substantially the same shape and size as a bobbin case to hold a bobbin when the machine is to make lock stitches, said body member being detachably fitted into the loop taker, and having a movable grip plate disposed at the front of said body member to removably lock said body member in position in the loop taker.

5. The chain stitch forming device for a lock stitch sewing machine according to claim 1 wherein the loop taker has a bobbin-supporting pin positioned therein, the pin being formed with an annular groove at the furthest end;

and said body member comprises a vertically elongated hole engaging with said bobbin-supporting pin so as to permit the vertical movement of said upwardly projecting loopretaining member;

a stop lever having a base and an open end, the base being pivoted to said body member and the open end facing the annular groove of said bobbin-supporting pin;

resilient means located between said stop lever and body member and urging said stop lever to engage with said annular groove, thereby preventing said body member from coming off said loop taker and also urging said body member upwardly and manually operable means for disengaging said stop lever from said annular groove against the action of said resilient means.

6. The chain stitch forming device for a lock stitch sewing machine according to claim 5 wherein said elongated hole further has a predetermined width in the direction of said bobbin-supporting pin and an inclined upper end surface, said inclined upper end surface being engageable by said cam means to shift the top of said loop-retaining member to a point removed from the released loop after the top of said loop retaining member is brought down to below the level of said stationary threaded guide.

7. The chain stitch device for a lock stitch sewing machine according to claim 5 wherein said manually operable means comprises a grip plate fitted to said body member and located to rise or fall as required at the front part of said body member in order to disengage said stop lever from said annular groove;

and a spring for normally keeping said grip plate in lowered state, thereby enabling said stop lever to be disengaged from said annular groove when said grip plate is made to rise against the action of said spring.

8. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support formed with a needle aperture, a needle with a thread carrying eye positioned above said support and capable of making vertical reciprocations through the needle aperture, a needle thread takeup mechanism disposed on the frame for alternately tightening and loosening the needle thread in timed relationship with the vertical reciprocations of the needle, a loop taker housing secured to said frame and having an internal circular raceway, a bobbin case, a loop taker having a discontinuous peripheral bearing rib journaled in said raceway for oscillating movement around a horizontal axis and adapted to accommodate said bobbin case, a stop means for preventing said bobbin case from making oscillating movement together with said loop taker, means for driving said needle and loop taker in prescribed timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of said needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker, and a linear feeding mechanism of a work fabric held on its support member for advancing it in a prescribed direction from the needle aperture during the reciprocations of said needle, said chain stitch forming device comprising a chain stitch forming member fitted into said loop taker in replacement of said bobbin case, an upwardly projecting loop-retaining member mounted on said chain stitch forming member in a manner to be located close to said needle aperture, means shiftably mounting said loop-retaining member for movement between an upper loop-retaining position and a lower loop releasing position; 1

means normally biassing said loop retaining member into said upper loop-retaining position;

a stationary thread guide interposed between said loopretaining member and said needle aperture at a point lower than a maximum height attained by the top of said loop-retaining member so as to temporarily retain the loop on said loop-retaining member after being released from said loop taker, and cam means provided on said loop taker to engage the chain stitch forming device for a predetermined time during each stitch cycle to lower the top of said loop-retaining member below the level of said stationary thread guide as a result of the oscillating movement of said loop taker so as to allow the loop retained on said loop-retaining member to be moved therefrom by the thread takeup mechanism after said needle passes through said loop on its next stitching cycle thereby forming chain stitches with threads carried by said needle.

9. The chain stitch forming device for a lock stitch sewing machine according to claim 8 wherein said cam means on the loop taker is formed on the curved overhanging lip of the front loop expanding wall thereof.

10. The chain stitch forming device for a lock stitch sewing machine according to claim 8 including a bridge member fitted on the loop taker housing and the stationary thread guide formed in the bridge member.

11. The chain stitch forming device for a lock stitch sewing machine according to claim 10 wherein said bridge member is formed with a loop-restricting portion located close to said loop-retaining member to prevent the loop released from said loop taker, while being temporarily retained by said loop retaining member, from passing over the top of said loopretaining member due to the lifting action of said thread takeup mechanism and being pulled through the space between loop-retaining member and the stationary thread guide.

12. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support formed with a needle aperture, a thread carrying eyed needle supported about the work support for endwise reciprocation through said needle aperture, a needle thread takeup mechanism mounted on said frame for alternately tightening and loosening said needle thread in timed relationship with the endwise reciprocation of said needle, a loop taker disposed on said frame rotatably about the axis of the loop taker assembly, a bobbin case retainer supported in said loop taker and adapted to accommodate a bobbin case, said bobbin case retainer being provided with a recess near said point of needle penetration, a restraining member, the base of which is fixed to said frame and the end of which has a projection freely engaging with said recess so as to prevent said bobbin case retainer from rotating together with said loop taker, means for driving said needle and loop taker in timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of the needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker, and a linear work-feeding mechanism for advancing said work fabric carried on its support in a prescribed direction from said needle aperture during each endwise reciprocation of said needle characterized in that it further comprises a body member fitted into a bobbin case retainer in replacement of said bobbin case, an upwardly projecting loop retaining member disposed on said body member on the workfeeding side close to the point of needle penetration, means connected to said loop retaining member so as to urge it upwardly, a stationary thread guide formed on the projection of said restraining member for temporarily retaining the loop released from the loop taker on said loop-retaining member in cooperation therewith and cam means formed on said loop taker engaging, and bringing the top of said loop retaining member down to below the level of said stationary thread machine according to claim 12 wherein the stationary thread guide is open and formed in the projection of said restraining member, the bottom plane of said guide being positioned lower than a maximum height attained by the top of said loop retaining member.

Claims

1. A chain stitch forming device for a lock stitch sewing machine, said machine including a frame having a work support formed with a needle aperture; a thread-carrying eyed needle disposed above the work support for endwise reciprocation through said needle aperture; a needle thread takeup mechanism mounted on said frame for alternately tightening and loosening said needle thread in timed relationship with the endwise reciprocation of said needle; a loop taker disposed on said frame for circularly moving about the axis of the loop taker assembly, said loop taker being formed with a bobbin-receiving cavity to accommodate a bobbin; stop means for preventing the bobbin from making circular movement together with said loop taker, means for driving said needle and loop taker in timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of the needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker; and a linear work-feeding mechanism for advancing said work fabric carried on its support in a prescribed direction from said needle aperture during each endwise reciprocation of said needle; wherein said chain stitch forming device comprises a body member formed to be fitted into the cavity of said loop taker in replacement of a bobbin; an upwardly projecting loop-retaining member disposed on said body member on the work-feeding side close to the point of needle penetration; means connected to said loop-retaining member to urge it upwardly; a stationary thread guide interposed between said loop-retaining member and said point of needle penetration positioned at a point lower than the maximum height attained by the top of said loop-retaining member to temporarily retain the loop released from the loop taker on said loop-retaining member by cooperation of said thread guide and said loop-retaining member; and cam means located between said loop taker and said loopretaining member operating in synchronism with the needle and engaging said loop retaining member to move the top of said loop-retaining member down to below the level of said stationary thread guide as a result of the circular movement of said loop taker and to allow the loop retained on said loopretaining member to be taken off therefrom by said thread takeup mechanism after said needle, upon being brought down during a subsequent stitch-forming movement passes through said loop, thereby forming chain stitches with threads carried by said needle.

4. The chain stitch forming device for a lock stitch sewing machine according to claim 1 wherein said body member is formed to fit the bobbin cavity and is of substantially the same shape and size as a bobbin case to hold a bobbin when the machine is to make lock stitches, said body member being detachably fitted into the loop taker, and having a movable grip plate disposed at the front of said body member to removably lock said body member in position in the loop taker.

5. The chain stitch forming device for a lock stitch sewing machine according to claim 1 wherein the loop taker has a bobbin-supporting pin positioned therein, the pin being formed with an annular groove at the furthest end; and said body member comprises a vertically elongated hole engaging with said bobbin-supporting pin so as to permit the vertical movement of said upwardly projecting loop-retaining member; a stop lever having a base and an open end, the base being pivoted to said body member and the open end facing the annular groove of said bobbin-supporting pin; resilient means located between said stop lever and body member and urging said stop lever to engage with said annUlar groove, thereby preventing said body member from coming off said loop taker and also urging said body member upwardly and manually operable means for disengaging said stop lever from said annular groove against the action of said resilient means.

6. The chain stitch forming device for a lock stitch sewing machine according to claim 5 wherein said elongated hole further has a predetermined width in the direction of said bobbin-supporting pin and an inclined upper end surface, said inclined upper end surface being engageable by said cam means to shift the top of said loop-retaining member to a point removed from the released loop after the top of said loop retaining member is brought down to below the level of said stationary thread guide.

7. The chain stitch device for a lock stitch sewing machine according to claim 5 wherein said manually operable means comprises a grip plate fitted to said body member and located to rise or fall as required at the front part of said body member in order to disengage said stop lever from said annular groove; and a spring for normally keeping said grip plate in lowered state, thereby enabling said stop lever to be disengaged from said annular groove when said grip plate is made to rise against the action of said spring.

8. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support formed with a needle aperture, a needle with a thread carrying eye positioned above said support and capable of making vertical reciprocations through the needle aperture, a needle thread takeup mechanism disposed on the frame for alternately tightening and loosening the needle thread in timed relationship with the vertical reciprocations of the needle, a loop taker housing secured to said frame and having an internal circular raceway, a bobbin case, a loop taker having a discontinuous peripheral bearing rib journaled in said raceway for oscillating movement around a horizontal axis and adapted to accommodate said bobbin case, a stop means for preventing said bobbin case from making oscillating movement together with said loop taker, means for driving said needle and loop taker in prescribed timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of said needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker, and a linear feeding mechanism of a work fabric held on its support member for advancing it in a prescribed direction from the needle aperture during the reciprocations of said needle, said chain stitch forming device comprising a chain stitch forming member fitted into said loop taker in replacement of said bobbin case, an upwardly projecting loop-retaining member mounted on said chain stitch forming member in a manner to be located close to said needle aperture, means shiftably mounting said loop-retaining member for movement between an upper loop-retaining position and a lower loop releasing position; means normally biassing said loop retaining member into said upper loop-retaining position; a stationary thread guide interposed between said loop-retaining member and said needle aperture at a point lower than a maximum height attained by the top of said loop-retaining member so as to temporarily retain the loop on said loop-retaining member after being released from said loop taker, and cam means provided on said loop taker to engage the chain stitch forming device for a predetermined time during each stitch cycle to lower the top of said loop-retaining member below the level of said stationary thread guide as a result of the oscillating movement of said loop taker so as to allow the loop retained on said loop-retaining member to be moved therefrom by the thread takeup mechanism after said needle passes through said loop on its next stitching cycle thereby forming chain stitches with threads carried by said needle.

11. The chain stitch forming device for a lock stitch sewing machine according to claim 10 wherein said bridge member is formed with a loop-restricting portion located close to said loop-retaining member to prevent the loop released from said loop taker, while being temporarily retained by said loop retaining member, from passing over the top of said loop-retaining member due to the lifting action of said thread takeup mechanism and being pulled through the space between loop-retaining member and the stationary thread guide.

12. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support formed with a needle aperture, a thread carrying eyed needle supported about the work support for endwise reciprocation through said needle aperture, a needle thread takeup mechanism mounted on said frame for alternately tightening and loosening said needle thread in timed relationship with the endwise reciprocation of said needle, a loop taker disposed on said frame rotatably about the axis of the loop taker assembly, a bobbin case retainer supported in said loop taker and adapted to accommodate a bobbin case, said bobbin case retainer being provided with a recess near said point of needle penetration, a restraining member, the base of which is fixed to said frame and the end of which has a projection freely engaging with said recess so as to prevent said bobbin case retainer from rotating together with said loop taker, means for driving said needle and loop taker in timed relationship in such a manner that while said needle is being brought downwardly through said needle aperture, the loop coming out of the needle eye is seized by said loop taker and that while said needle is being brought upwardly, the seized loop is released from said loop taker, and a linear work-feeding mechanism for advancing said work fabric carried on its support in a prescribed direction from said needle aperture during each endwise reciprocation of said needle characterized in that it further comprises a body member fitted into a bobbin case retainer in replacement of said bobbin case, an upwardly projecting loop retaining member disposed on said body member on the work-feeding side close to the point of needle penetration, means connected to said loop retaining member so as to urge it upwardly, a stationary thread guide formed on the projection of said restraining member for temporarily retaining the loop released from the loop taker on said loop-retaining member in cooperation therewith and cam means formed on said loop taker engaging, and bringing the top of said loop retaining member down to below the level of said stationary thread guide as a result of rotary movement of said loop taker so as to allow the loop retained on said loop-retaining member to be taken off therefrom by said needle thread takeup means after the needle being brought down next time passes through said loop, thereby forming chain stitches with threads carried by said needle.

13. The lock stitch forming device for a lock stitch sewing machine according to claim 12 wherein the stationary thread guide is open and formed in the projection of said restraining member, the bottom plane of said guide being positioned lower than a maximum height attained by the top of said loop retaining member.