US3570429A

US3570429A - Thread guide for a rotary-hook-type sewing machine

Info

Publication number: US3570429A
Application number: US811854A
Authority: US
Inventors: Susanna Bolt; Harald Swifarth
Original assignee: Mefina SA
Current assignee: Mefina SA
Priority date: 1968-04-18
Filing date: 1969-04-01
Publication date: 1971-03-16
Anticipated expiration: 1988-03-16
Also published as: BE730827A; SE362668B; CH473261A; BR6907527D0; NL6904639A; AT297463B; IE33026L; DK132452C; DE1914516A1; IE33026B1; DK132452B; FR2006408A1; GB1204096A; JPS4816213B1; ES365694A1

Abstract

A blade or wire, mounted underneath the cover for the guard ring and in the path of the underthread on its way to the needle, is so shaped that when the sewer pulls the underthread tight, while threading the machine preparatory to sewing, it is caused to move under the tension skid automatically.

Description

United States Patent Susanna Bolt Geneva;

Harald Seifarth, Chatelaine-Geneva, Switzerland Apr. 1, 1969 Mar. 16, 1971 Melina S.A. Fribourg, Switzerland Apr. 18, 1968 Switzerland [72] Inventors Appl. No. Filed Patented Assignee Priority THREAD GUIDE FOR A ROTARY-HOOK-TYPE SEWING MACHINE 3 Claims, 4 Drawing Figs.

us. Cl

[5 1 r n c1.. ..D05b57/10 5 WI/AIYlll/I/l/l/l/ [50] Field of Search 112/184, 260, 233, 232, 228, 229, 231

[5 6] References Cited 7 UNITED STATES PATENTS 1,188,818 6/1916 Parkes 112/233 2,232,624 2/1941 Nissen 112/233 2,488,052 11/1949 Casas Robert.... 112/233 3,011,463 12/1961 Fujita 112/260 Primary ExaminerI-I. Hampton Hunter Attorneys-Emory L. Groff and Emory L. Groff, Jr.

ABSTRACT: A blade or wire, mounted underneath the cover for the guard ring and in the path of the underthread on its way to the needle, is so shaped that when the sewer pulls the underthread tight, while threading the machine preparatory to sewing, it is caused to move under the tension skid automatically.

Ptentd March 16, 1971 3,570,429

2 Sheets-Sheet l INVENTORS Sum/m4 B04 A ma/mp SE/FA PT/I ATTORNEY Meme 357,29

2 Sheets-Sheet a 38 h 36 I 1 I 39 ya i L 36 f 3 2 0 INVENTORS BY m ATTORNEY THREAD GUIDE FOR A ROTARY-HOOK-TYPE SEWING MACHINE The invention relates to the combination in a rotary-hooktype sewing machine of a bobbin case carrying the underthread, a guard ring for holding the bobbin case, and an arrangement including a skid for adjusting the tension of the underthread.

When the sewer threads her machine preparatory to sewing, she must guide the underthread by hand under the skid of the tensioning arrangement. Since this step in the threading operation is rather tedious, it is desirable to make it as quick and simple as possible.

In accordance with the invention, this step is made entirely automatic.

An object of the invention is a guide means for automatically moving the underthread under the skid when the sewer pulls upon it while threading her rotary-hook-type sewing machine.

This object and others of the invention will be apparent from the following detailed description, wherein the sewing machine has a free lower arm. 1

The invention will be described, with reference of the drawings, wherein:

FIG. l is a transverse section through the lower arm of the sewing machine;

FIG. 2 is a top view, partly cut away, of the front end of the lower arm;

FIG. 3 is a longitudinal section of the front part of the lower arm; and

FIG. 4 is a view similar to that of FIG. 3 but of another form of the invention, showing only the modified parts.

With reference to the FIGS. of the drawings the sewing machine comprises a free lower arm 1 within which is arranged the feed mechanism for the cloth. This mechanism is shown in the FIGS. only by the feed dog 3, the teeth of which project into openings 4 in the needle plate 5, which also has an elongated opening 6 to permit the needle 7 to move in its two extreme transverse positions when zigzag stitching. The needle 7 is fixed at the end of the needle bar 2 which is driven by a mechanism held in the head of the sewing machine, the head not being shown. A pressure foot 9 holds the cloth against the needle plate 5.

The arrangement for the underthread 10 includes a bobbin case 12, which is held in a guard ring composed of upper and lower guard rings 14 and 13, respectively. The two parts 13 and 14 are held together by screws 15 and intermediate blade springs 16. Defined between the parts 13 and 14 is a groove 17 that enables the guard ring 13 and 14 to be guided on an annular rib 13 incorporated by the cup-shaped rotary hook 19, the point of which the reference numeral 20. The rotary hook 19 is carried by a shaft 21 arranged substantially vertically and continuously rotated when the sewing machine is running. A retaining nose 22, held by screws against the upper guard ring M, holds the guard ring 13 and 14 in a fixed position within the rotary hook 19. The nose 22 cooperates with a stop, which in the present instance forms part of a release device that opens up a space between the nose 22 and the stop of said device when the loop of needle thread encircles the bobbin case.

The underthread 10, wound in the bobbin case 12, leaves the case through a slot 25 in the upper guard ring 14 and in a cylindrical skirt 26 on this guard ring. The thread 10 continues to the edge of this skirt and then passes under a skid 27 forming part of an arrangement for regulating the tension of the underthread. Against this skid presses a spring 28 the tension of which is controlled by a lever 29 pivoted at 30. A tension-adjusting member 31 that can be turned about an axis and has an eccentric head 32 acts on the end 33 of the lever 29, and varies the tension of the spring 28 on the skid 27 when turned. After the thread 10 leaves the skid 27 it enters a slot 34 in the cylindrical skirt 26 and takes the path towards the needle 7.

A cover 35, positioned substantially coplanar with the needle plate 5, is arranged horizontally above the bobbin case 12 to the FIGS.

and the rotary hook 19. In the embodiment illustrated in FIGS. 1 to 3, the cover 35 is mounted free to slide transversely with respect to the free lower arm 1. To this end, the lower face of the cover carries two tongues 36, which engage respective rails 37 of the lower arm 1. These tongues are formed in either end of a metal strip 38 held against the lower face of the cover 35.

The cover carries an underthread guide 39 used while threading the machine preparatory to sewing. In the form illustrated in FIGS. 1 to 3, the guide 39 consists of the edge of a blade 40 held at a slant under the cover 35. In this particular embodiment, the blade 40 is formed by a lateral prolongation of the metal strip 38, the prolongation being bent at an angle with respect to the strip. An underthread guide slot 41 is incorporated in the edge 42 of the cover 35. The under thread 10 slides over the edge 42 while the sewing machine is being threaded.

The machine is threaded preparatory to sewing in the following manner:

The cover 35 is opened and a bobbin case 12 of underthread 10 is placed in the guard ring 13 and 14. Thereupon the thread 10 is threaded through the slot 25 of the skirt 26, the cover 35 pushed back over the bobbin case 12, and the thread run through the slot 41 in the cover edge 42. The sewer now pulls on the thread 10 so as to stretch it tight between the slot 25 and the guide 39, thereby forcing it under the skid 27 (see FIG. 1). The guide 39 therefore ensures, as already noted, that the underthread is correctly positioned in the tension regulator, of which the skid 27 forms one part. This much done, the first step of preparing the machine for sewing is completed. The sewer must now pass the needle thread (not shown) through the eye of the needle 7 and then turn the handwheel manually until the needle has completed its first downward movement. When the needle is at the bottom of its stroke, the rotary hook point 20 catches the needle thread guided by the needle and forms a loop which it encircles about the guard ring 13 and 14 and therefore about the bobbin case 12 of underthread 10. The loop of needle thread at the same time grips the free end of the underthread 10. The sewer next pulls on the end of the needle thread, causing both the loop, now closed, and the end of the underthread 10 to be brought up through the opening 6. The ends of the two threads are then laid down flat on the needle plate 5, and the sewer can position them under the pressure foot 9 to make the desired stitch.

FIG. 4 shows a second form of the invention, in which the cover 35 is not slidingly mounted on the lower arm 1 but is hinged thereto by two arms 43. The guide 39 consists in this case of a metal wire fixed at a slant between the lower face of the cover 35, and one of the hinge arms 43.

One skilled in the art will recognize at once that various other embodiments lie within the scope of the invention. The guide 39, for example, can consist of any suitable part mounted underneath the cover 35.

The invention as described with reference to the FIGS. of the drawing was applied to a sewing machine having a rotary hook rotating about a substantially vertical axis. The guide 39 can also be employed, of course, in a sewing machine with a rotary hook turning on a horizontal axis or in one with any other arrangement of bobbin case and rotary hook. Instead of being mounted on the cover 35, the guide 39 can be carried by any other part of the lower arm 1, for example.

Although the preferred embodiments have been described, the scope of, and the breadth of protection afforded to, the in vention are limited solely by the appended claims.

We claim:

1. The combination in a rotary-hook-type sewing machine including a needle plate, a bobbin case carrying the underthread, a guard ring for holding said bobbin case, a tension regulator including a skid for adjusting the tension of the underthread, a movable cover for said bobbin case and said rotary hook, the improvement comprising underthread guide means for controlling the path taken by the underthread while threading the sewing machine preparatory to sewing so that the underthread automatically moves under said skid when the sewer pulls upon the underthread, said guide means comprising a blade fixed at a slant underneath said cover, said blade defining a slanted guide edge constituting said guide means proper and which is positioned in the path of the underthread on its way from said bobbin case to the needle plate of the machine so that when the underthread is tensioned against said slanted guide edge and pulled along its path from the bobbin case to the needle plate, said underthread is constrained in a lateral direction along said slanted guide edge to automatically move under said skid.

2. The combination in a rotary-hook-type sewing machine including a needle plate, a bobbin case carrying the underthread, a guard ring for holding said bobbin case, a tension regulator including a skid for adjusting the tension of the underthread, a cover for said bobbin case and the rotary hook, a pair of arms hinging said cover to the lower arm of the sewing machine, the improvement comprising underthread guide means for controlling the path taken by the underthread while threading the sewing machine preparatory to sewing so that the underthread automatically moves under said skid when the sewer pulls upon the underthread, said guide means comprising a wire fixed at a slant between the lower face of said cover and one of said hinge arms and positioned in the path of the underthread on its way from said bobbin case to the needle plate of the machine so that when the underthread is tensioned against said slanted wire and pulled along its path from the bobbin case to the needle plate, said underthread is constrained in a lateral direction along said slanted wire to automatically move under said skid.

3. The improvement as defined in claim 1, wherein said cover has an edge over which the underthread slides on its way to the needle plate when the sewing machine is being threaded preparatory to sewing and when the machine is in use, said cover edge having a slot through which the underthread passes for guiding said underthread.