US3596620A

US3596620A - Rotary looptaker for lockstitch sewing machines

Info

Publication number: US3596620A
Application number: US208A
Authority: US
Inventors: Willi Vogel
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1969-03-07
Filing date: 1970-01-02
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: FR2034711A1; GB1240085A; DE1911562B1; CH496131A; SE352115B

Abstract

In a rotary looptaker for lockstitch sewing machines of the type comprising a rotating cup-shaped looptaker body having a circular raceway engaged by the bearing rib of a stationary bobbin case, said raceway being formed by a shoulder on the inside edge of the cylindrical sidewall of said body and a ring-shaped cove overlying the recess formed by said shoulder, the looptaker body is subdivided into a plurality of segments by slits extending from a reinforced central bottom portion thereof radially outwardly and along the cylindrical wall in a direction parallel to the looptaker axis. The segments with their shoulders forming part of the raceway are elastically connected and the cover forming the remaining part of the raceway is rigidly connected with the central bottom portion of the looptaker body.

Description

United States Patent Inventor Appl. No. Filed Patented Assignee Priority ROTARY LOOPTAKER FOR LOCKSTITCH SEWING MACHINES 8 Claims, 5 Drawing Figs.

US. Cl. 1 12/228 Int. CL D0511 57/14 Field ofSeareh 112/228,

References Cited UNITED STATES PATENTS 2/1918 Leathem 112/228 1,596,487 8/1926 l-lohmann et al 1 12/228 3,465,700 9/1969 Kuhar 1 12/228 FOREIGN PATENTS 913,799 12/1962 Great Britain 112/228 Primary Examiner Alfred R. Guest Attorney-Greene & Durr ABSTRACT: ln a rotary looptaker for lockstitch sewing machines of the type comprising a rotating cup-shaped looptaker body having a circular raceway engaged by the bearing rib of a stationary bobbin case, said raceway being formed by a shoulder on the inside edge of the cylindrical sidewall of said body and a ring-shaped cove overlying the recess formed by said shoulder, the looptaker body is subdivided into a plurality of segments by slits extending from a reinforced central bottom portion thereof radially outwardly and along the cylindrical wall in a direction parallel to the looptaker axis. The segments with their shoulders forming part of the raceway are elastically connected and the cover forming the remaining part of the raceway is rigidly connected with the central bot tom portion of the looptaker body.

PATENTEIJ nus 31971 3; 596, 620

4 sum 2 or 2 INVI-SNTOR W/ L-L-l VOG-EA- fTHRL. BATH A rromv EY ROTARY LOOPTAKER FOR LOCKSTITCI-I SEWING I MACHINES raceway is formed by an offset or shoulder on the inner edge 1 of the cylindrical sidewall of the looptaker body and a covering ring overlying the recess formed by said shoulder and secured to said body.

Known looptaker constructions of this type have the disadvantage of jamming or looking as a result of the penetration of foreign bodies or particles, such as pieces of thread known as sewing dust, into the space between the raceway of the looptaker body and the bearing rib of the bobbin case. The threads or other foreign particles, upon penetration, cause a considerable increase of the friction between the raceway and bearing rib due to relative canting of the parts. While the bearing rib is commonly provided with transverse slots designed to cut the caught threads, it is found that the results obtained are unsatisfactory in practice due to the fact that rotation of the looptaker is blocked after jamming by a thread or other foreign particle, preventing thereby a transfer of the particles to the next slot of the rib for removal. Besides, since the slots do not move during rotation of the looptaker, they act as collecting points of the thread dust or other foreign particles.

There are already known rotary looptaker constructions, wherein a part of the looptaker raceway is enabled to yield resiliently in the radial direction. Other constructions make it possible, in the case of a foreign body penetrating the looptaker raceway, for the cover ring forming part of the raceway to yield in the axial direction of the looptaker body. In other words, all the known constructions have in common that the raceway is enabled to yield in a single direction only, that is, either radially or axially, resulting thereby in a partial or practically unsatisfactory solution only of the problem of preventing jamming or blocking of the looptaker due to foreign matter entering the looptaker raceway.

Accordingly, an important object of the present invention is the provision of an improved looptaker construction of the referred to type which is substantially devoid of the aforementioned and related drawbacks and shortcomings by ensuring a positive and accurate positioning of the bobbin case of the looptaker, substantially independently of penetrations of thread dust or other foreign particles into the raceway of the looptaker body, to thereby securely and positively prevent jamming or blocking of the looptaker parts.

A more specific object of the invention is the provision of simple and efficient means capable of accomplishing the foregoing objects and suitable for structural incorporation in conventional looptaker structures of the referred to type.

The invention, both as to the foregoing and ancillary objects as well as novel objects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this disclosure and wherein:

FIG. 1 is an exploded" perspective view, showing the parts of one form of a rotary looptaker constructed in accordance with the principles of the invention;

FIG. 2 is an elevational view, shown partly in section, of the parts according to FIG. 1 assembled into an operative looptaker unit;

FIG. 3 is a fragmentary side view, to an enlarged scale, of FIG. 2;

FIG. 4 is a plan view of an alternative looptaker construction according to the invention, shown with the bobbin case removed; and

FIG. 5 is a partial sectional view taken on line V-V of FIG. 4.

Like reference numerals denote like parts in the different views of the drawings.

With the foregoing objects in view, the invention involves principally the subdivision of the looptaker body or raceway respectively into a plurality of parts or segments capable of elastically yielding in both the radial and axial directions in respect to the looptaker axis.

More particularly, the foregoing object is achieved by the provision of a number of radial slits in the cup-shaped looptaker part orbody including the shoulder or offset forming part of the looptaker raceway, said slits extending from a 0 preferably reinforced central bottom portion or zone of said body radially along and to the edge of the cylindrical wall thereof, whereby to provide a number of segments elastically connected with said central zone, with further means being provided to rigidly connect the cover ring, forming the remainder of the looptaker raceway, with said central bottom zone. With the cylindrical wall of the looptakerbody being normally interrupted and shaped with one end terminating in a looptaker beak, the cover ring being advantageously similarly interrupted is shaped to form a point extending into a recess of the looptaker beak.

The required elasticity of the connection between the individual looptaker segments and the central body portion may be achieved by the use of a suitable material and/or construction of the connecting parts, such as a reduction of the cross section of said parts. More specifically, the connections intervening between the looptaker raceway and the central bottom zone of the looptaker body should have an elasticity such that the segments offer a predetermined and adequate resistance against deformation by the normal stress or load obtaining during rotation of the looptaker, to substantially prevent deflection during normal operation. On the other hand, if a thread or other foreign particle enters the looptaker raceway, resulting thereby in said resistance exceeding the predetermined limit value so as to cause jamming of the raceway with the bearing rib of the bobbin case, the respective segment in the vicinity of the point of entering of the foreign body or bodies is deflected both in the radial and axial directions, while allowing the remaining segments to retain their normal positions, to ensure or maintain a uniform guidance of the bobbin case bearing rib.

According to a preferred embodiment of the invention the looptaker body is composed of two cup-shaped parts, one mounted concentrically within the other with their cylindrical sidewalls at a predetermined spacing distance and with their bottom walls firmly connected with one another. In this case, the inner part being split into segments is formed with the offset or shoulder forming part of the looptaker raceway, while the outer part serves for the mounting of the cover ring forming the remaining raceway part of the looptaker. In order to prevent excessive outward deflection of the segments, the outer part may be provided with striplike projections forming abutments positioned opposite and centrally in respect to said segments.

According to an alternative embodiment of the invention, the segments of a single cup-shaped looptaker body are connected alternately elastically and rigidly respectively with the central bottom zone of said body and the cover ring is connected to the segments which are rigidly connected with said bottom zone.

The shoulders of the elastically mounted segments together with the cover ring form the looptaker raceway in the manner of the first described embodiment, while the remaining rigidly mounted segments are formed with shoulders of a size in exwithin the former, and an interrupted cover ring 4 forming a circular raceway together with a shoulder of part 2 for engagement by the bearing rib of stationary looptaker body or bobbin case comprised, in the example shown, of a lower case 5 and an upper case 6, the latter being disposed within the former and containing the under thread bobbin 7. I

Part 1 has a bottom wall 8 whose outer surface is fitted with a hub 9, FIG. 2, for the mounting of the looptaker upon the looptaker drive shaft 10 of a conventional sewing machine. The bottom 8 is further fitted upon its inside surface with a centering rim or ring 11 and extends radially outwardly into the cylindrical side wall 12, the latter being interrupted, as at l and having an end thereof terminating into the looptaker point or beak 13 for the seizing of the needle thread loop during a stitch-forming operation.

Part 2 of the rotating looptaker body has a bottom14 and a cylindrical sidewall 15 being interrupted as at 2' and of lesser diameter than the sidewall 12 of part 1, to enable part 2 to be concentrically mounted within part 1 with an adequate clearance or intermediate space remaining between the sidewalls of the parts.

In the assembled position of the parts, FIG. 2, the centering ring 11 of part 1 engages a bore 16 in the bottom wall 14 of part 2 and a ringshaped reinforced central portion or zone 17 of part 2 engages the bottom of part 1. Part 2 is firmly secured to the part 1 by means of countersunk screws 18, to form a composite looptaker unit 3, FIG. 2. For this purpose, the heads of the screws 18 engage conical depressions 19 in the central zone 17, while the shanks of the screws engage threaded bores 20 in the bottom of part 1 disposed radially outwardly of the centering ring 1 1.

The marginal zone of the cylindrical wall 15 of the part 2 is formed with an outwardly thickened or reinforced portion or rim 21 whose inner edge is offset, to provide a shoulder 22. The part 2 is furthermore subdivided into a plurality or preferably equal segments 24 by the provision of slits 23 starting at points outside of the central zone 17 of the bottom wall 14 and extending at first radially outwardly along said bottom wall and in the axial direction along and to the edge the sidewall 15. As a consequence the segments 24 are connected with the reinforced central zone 17 in such a manner as to enable the same to give or yield by elastic deformation, in both radial and axial directions in respect to the looptaker axis, under the influence of a deflecting force exceeding a predetermined minimum value. This may be achieved by a proper design (reduced thickness or cross section and choice of materials) of the parts between the central and marginal portions 17 and 21.

Advantageously, the portions of the wall 12 opposite to and coincident with the segments 24 are provided with striplike projections or abutments 25 parallel to the looptaker'axis, to limit the outward deflection of said segments.

The cover ring 4 is secured to the wall 12 of the looptaker part 1 by means of screws 26 which advantageously engage threaded bores 27 provided in the reinforced parts or abutments 25 of the wall, as shown in the drawings.

The interrupted cover ring 4 terminates at one end thereof in a point 28 positioned below the looptaker beak 13. To this end, the looptaker beak projects beyond the edge of the wall 12 of the part 1 and covers with its enlarged portion 29, FIG. 3, both the point 28 of the ring 4 as well as the point 30 of the segment 24 adjoining the beak 13 point 30 being in turn covered by the point 28. As a consequence, the needle thread loop seized by the looptaker beak 13 is prevented from entering the space between part 1 and the ring 4 or part 2 respectively, ensuring thereby a proper guidance of the thread by the outer surface of the ring 4.

The shoulder 22 of the looptaker part 2 together with the covering ring 4 forms a raceway for the bearing rib 31 of the lower case 5 of a conventional bobbin case having an upper case 6 supporting the underthread bobbin 7. The looptaker furthermore includes a thread guide plate 33 secured, by the aid of screws 32, to the outer surface of the wall 12 of part 1.

The guide plate 33 has a thread guiding edge 34 spaced radially from and obliquely intersecting the looptaker beak l3, and a thread drawoff edge 35.

In operation, if a piece of thread or other foreign matter penetrates into the looptaker raceway and gets jammed between the latter and the bearing rib 31 of the bobbin case, the segment 24 in the vicinity of the jamming point gives way or yields, by virtue of its elasticity, in both radial and axial directions in respect to the looptaker axis, substantially without affecting the remaining segments 24 of the looptaker body. In contrast to the known arrangements, there is thus ensured by the invention an accurate guidance of the rib 31 of the bobbin case in the raceway of the looptaker body 3. The abutments 25 opposite the segments 24 prevent excessive deviation or deflection of the segments.

The jammed foreign particle is carried along by friction with the rotating looptaker part 2 and ejected outwardly by centrifugal action through theslits '23, in the same manner as any sewing dust entering the looptaker raceway.

As pointed out, adequate elasticity of the segments 24 may be achieved by suitable construction of the pants, such as by the part 2 having a lesser thickness than the part 1 as shown, or by using different materials, that is, with part 2 having a greater elasticity than part 1, in a manner readily understood.

The bobbin case 5 is furthermore shown provided with a notch 36 which in a known manner cooperates with a stationa ry rotation-restraining tongue (not shown), to provide an escape gap for the needle thread loop upon being cast around the case and pulled up by the thread takeup lever of the sewing machine, to interlock with the bobbin thread for the formation of lockstitches in accordance with conventional stitchforming operation.

According to the alternative embodiment of the invention shown by FIGS. 4 and 5, the looptaker body 41 consists of a single cup-shaped part replacing the two-part body 3 composed of parts 1 and 2 according to the embodiment of FIGS. 13. Again, the cylindrical wall 42 and the outer portion of the bottom wall 43 of the body 41 are provided with slits 44 extending radially outwardly from the central portion or zone 45 of the bottom 43 and along the cylindrical wall portion 42, whereby to subdivide the outer part of the body into a number of alternately broad and

narrow segments

46 and 47 respectively. The inside edges of the marginal zones of the side walls 42 of the broad segments-46 are offset, to provide shoulders 48 forming part of the looptaker raceway. Similarly, the walls 42 of the narrow segments 47 have their inner edges formed with offsets 49 which are slightly larger than the corresponding offsets 48 of the segments 46.

Secured to the rigid segments 47, by means of screws 51, is the interrupted covering ring whose point 52 underlies, in the same manner as in the embodiment of FIGS. 1-3, enlarged portion 53 of the looptaker beak 54 forming part of the body 41.

In other words, whereas the segments 47 are connected rigidly with the central zone 45 of the bottom 43, each of the intervening segments 46 is connected with said zone through an elastic intermediate part 55. As a consequence, the segments 46 are enabled to give or yield, upon penetration of a thread or other foreign particle into the looptaker raceway formed by the shoulder 48 and the ring 50, by elastic deformation or bending of the respective section 55, in substantially the same manner as described in reference to the first embodiment and without affecting the remaining segments 46 or sections 55, respectively.

Excessive deflection of the segments 46 is prevented, in the example shown, by the thread guide plate 56 secured, by the aid of screws 57, to the rigid segments 47 which latter have a slightly larger radius than the peripheral walls of the segments 46.

In the foregoing the invention has been described in reference to preferred exemplary devices. It will be evident, however, that variations and modifications, as well as the substitution of equivalent parts for those shown herein for illustration, may be made without departing from the broader purview and spirit of the invention.

I claim:

l. A looptaker for lockstitch sewing machines comprising in combination:

1. a rotary cup-shaped looptaker body having a bottom wall and an interrupted cylindrical sidewall shaped with one end terminating in a looptaker beak,

2. an interrupted ring-shaped cover secured to said sidewall, to provide a circular raceway together with a shoulder upon the inner edge of said sidewall,

. said body being subdivided into a plurality of segments by angularly spaced slits extending radially outwardly from a central portion of said bottom wall and along said sidewall in a direction parallel to the axis of said body,

4. a stationary bobbin case having a bearing rib disposed within said raceway, and

5. means to cause at least part of said segments forming said raceway together with said cover to be joined to said bottom wall portion in both radially and axially yielding elastic connection therewith and to cause said cover to be rigidly connected to said bottom wall portion.

2. A rotary looptaker as claimed in claim 1, wherein said body consist of a pair of concentric cup-shaped inner and outer parts arranged with the central reinforced bottom portion of the inner part, being of relatively smaller diameter and slit into a plurality of segments, connected to the inside of the bottom wall of the outer part of relatively greater diameter and with said cover ring connected to the edge of said outer part and forming a raceway with shoulders on the inside edge of said segments.

3. A rotary looptaker as claimed in claim 2, including a plu rality of abutments projecting inwardly from the sidewall of said outer part, each of said abutments being positioned centrally in respect to the adjacent segment of said inner part.

4. A rotary looptaker as claimed in claim 2, wherein said inner looptaker part has a wall thickness being less than the wall thickness of said outer looptaker part.

5. A rotary looptaker as claimed in claim 2, wherein said inner looptaker part consists of a material of greater elasticity than said outer looptaker part.

6. A rotary looptaker as claimed in claim 1, wherein a set of first segments of said body of relatively greater elasticity alternates with second rigid segments and wherein the offsets of said first segments form said raceway together with said cover ring connected to said second segments, said second segments formed with offsets of a size in excess of said first offsets.

7. A rotary looptaker as claimed in claim 6, wherein said first segments include intermediate portions of reduced cross section compared with said first segments.

8. A rotary looptaker as claimed in claim 6, including a thread guide plate secured to the periphery of said second segments, to limit the radial deflection of said first segments.

Claims

1. A looptaker for lockstitch sewing machines comprising in combination: 1. a rotary cup-shaped looptaker body having a bottom wall and an interrupted cylindrical sidewall shaped with one end terminating in a looptaker beak, 2. an interrupted ring-shaped cover secured to said sidewall, to provide a circular raceway together with a shoulder upon the inner edge of said sidewall, 3. said body being subdivided into a plurality of segments by angularly spaced slits extending radially outwardly from a central portion of said bottom wall and along said sidewall in a direction parallel to the axis of said body, 4. a stationary bobbin case having a bearing rib disposed within said raceway, and 5. means to cause at least part of said segments forming said raceway together with said cover to be joined to said bottom wall portion in both radially and axially yielding elastic connection therewith and to cause said cover to be rigidly connected to said bottom wall portion.

3. A rotary looptaker as claimed in claim 2, including a plurality of abutments projecting inwardly from the sidewall of said outer part, each of said abutments being positioned centrally in respect to the adjacent segment of said inner part.

3. said body being subdivided into a plurality of segments by angularly spaced slits extending radially outwardly from a central portion of said bottom wall and along said sidewall in a direction parallel to the axis of said body,