EP0088113B1

EP0088113B1 - A rotating loop-taker in a sewing machine

Info

Publication number: EP0088113B1
Application number: EP82902839A
Authority: EP
Inventors: Leif Uno Larsen
Original assignee: Husqvarna AB
Current assignee: Husqvarna AB
Priority date: 1981-09-14
Filing date: 1982-09-13
Publication date: 1985-01-30
Also published as: SE8105458L; WO1983001078A1; DE3262158D1; EP0088113A1; SE428027B; JPS58501459A

Abstract

Improvement of a loop-taker of a sewing machine rotating around a shaft (3) fastened to the sewing machine body. The shaft is provided with a cam (6) which meshes with a cam follower (8) on one arm of a double lever arm (19), the other arm thereof supporting a loop-taker tip (10) and a needle guide (11). The position of the loop-taker tip in relation to the loop-taker body can then be changed during rotation enabling a better adaptation of the position of the loop-taker tip to the needle eye.

Description

The present invention is intended to bring about a rotating loop-taker in which a loop-taker tip can be adjusted to a needle eye position, when catching the upper thread loop.
When performing broad seams, a problem arises in taking the upper thread loop, owing to the fact that the needle eye position is changed in relation to the loop-taker tip, when the needle is moved laterally in sewing zig-zag and fancy seams.
In former design of such mechanisms it was assumed that the lateral movement of the needle must follow the circular path of the loop-taker tip, if the latter rotates in a horizontal plane, bringing about a rise in the price of the needle bar suspension and an increase of the mass forces.
Moreover, the loop-taker tip will arrive too late to the needle in the one extreme position and too early in the other extreme position, if the loop-taker has a perfect adjustment in the centre position. The circumstance is especially important in a loop-taker with a horizontal shaft.
According to the invention these drawbacks can be substantially eliminated by making the loop-taker tip movable in relation to the loop-taker body so that the tip can be adjusted to the needle eye position. Such an adjustment can e.g. decrease the demand for computer memory in computer controlled machines by the use of a loop-taker with a vertical shaft, as the lateral movement of the needle can be straight instead of arc-shaped and thus no computer controlled correction of the feeding with regard to such arc- shape will be necessary which it otherwise would be.
By the use of a loop-taker with a horizontal shaft the zig-zag width can be increased without the risk for missed stitches. A loop-taker with these advantages is characterized by the properties according to Claim 1.
An example of an embodiment of a loop-taker according to the invention is described in the following with reference to the accompanying drawings showing in:

Fig. 1 a cross section A-A of Fig. 2 illustrating the loop-taker and a bobbin cavity and stitch plate,
Fig. 2 the loop-taker without a bobbin, seen from above,
Fig. 3 a corrected path of the loop-taker tip following the several positions of the stitches, a, b, c, d and e and the seam produced when the feeding is zero, the needle position being seen from above,
Flg. 4 a corrected path of the loop-taker tip of a loop-taker with a horizontal shaft, and
Fig. 5 an exploded sketch of the loop-taker.

A loop-taker 1 according to Figs. 2 and 5 is provided with a toothed wheel 2 for driving and rotation in the direction of the arrow around a stationary shaft 3 secured in the sewing machine body 4 by means of a screw 5. The top end of the shaft 3 is a cam 6 constituting a curve 7 which meshes with a cam follower 8 on a lever arm 9 provided with a loop-taker tip 10 and a needle guide 11 which prevents the needle 12 from hitting the loop-taker tip when it passes the needle.
The lever arm 9 (Fig. 5) journalled by means of a pin 13 in the bearing 14 in the loop-taker is pressed by a leaf spring 15, fixed by means of the pin 16 in a hole 17 in the loop-taker, so that the cam follower 8 is held against the cam 6. The loop-taker tip 10 is movably disposed in a groove 18 in the loop-taker, and the lever arm 9 moves in a slot 20 and the needle guide 11 in a slot 19, so that the arm is kept in site against axial forces in the loop-taker.
A bobbin case 21, Figs. 1, 2 and 5 is journalled in the bearing 22 in the loop-taker by means of a flange 23.
The bobbin case has a cavity 24 for an under thread bobbin 25 including an under thread 26 which is pressed between a spring support 27 and a thread tension spring 28 fastened to the bobbin case by means of a screw 29. The under thread tension is adjusted by means of an adjusting screw 30 and the under thread is extended from the tension device through a slot 46, Figs. 2 and 5, to the hole 31 in the stitch plate (Fig. 1).
The bobbin case 21 is kept in site in the loop-taker by means of a pin 32 fastened by a screw 33 to the machine body 4. The bobbin case is further secured in the loop-taker by a bracket 34 including lugs 35, 36 and 37, which surround a corner 39 and a retainer 38 above a flange 40 on the bobbin case.
The bracket is fastened to the machine body 4 by a screw 41. Between the pin 32, the lugs 35, 36 and 37, the retainer 38 and the bobbin case there is a fissure in which a loop of the upper thread, formed when the thread 42 (Fig. 1) is taken by the loop-taker tip 10, can be guided around the bobbin case 21 when the loop-taker rotates. The dog 43 on the loop-taker tip (Figs. 1 and 5) guides the upper portion of the loop above the flange 44 of the bobbin case, while a notch 45 guides the lower portion of the loop beneath the bobbin case, whereupon the loop catches the under thread 26 and forms a stitch.
When the loop-taker rotates around the stationary cam 6 the cam follower 8 must follow the correcting curve 7, because it is pressed to the cam both by the spring 15 and the centrifugal force which acts on the heavier portion of the arm, where the loop-taker tip is positioned. The curve is so designed that the loop-taker tip leaves the usual circular path and corrects itself to the position of the needle eye, when the upper thread loop 42 is formed.
Fig. 3 is an example of a seam which can simply be sewn with the use of a correction of the path of the loop-taker tip. This path is seen from above, and the distances between a, b, c etc. are shown in enlargement.
In the Figure the arrow 47 denotes the normal direction of feeding of the cloth, while a, b, c, d and e denote the sequence of different needle positions used for producing the stitches f, g, h, i and j. By the way of correction of the path of the loop-taker tip by the distance I of the needle position c, it is provided a straight seam f, g, h, i and j without a correction of the cloth feeding. Thanks to this the saving of computer memory in computer controlled sewing machines is achieved as mentioned in the introduction.
Fig. 4 shows the path of a loop-taker tip of a loop-taker with a horizontal shaft and a needle position m in the right extreme position, the needle position n in the centre position and the needle position o in the left extreme position at the time when the loop-taker tip is about to catch the upper thread loop. If the needle has a perfect adjustment of the distance q between the needle eye and the loop-taker tip for taking the loop in the centre position n the distance p in the left position o will be too great and the distance r in the right position too small. By the way of correction of the loop-taker tip according to Fig. 3 so that the distance is q in all positions, it is possible to reach a better safety against missed stitches.
This description relates to a loop-taker with a vertical shaft and the tip is turned to the shaft. However, the invention could as well be applied to loop-takers turned from the shaft or to loop-takers with a horizontal shaft.

Claims

1. A rotating loop-taker of a sewing machine located on a loop-taker shaft disposed in the sewing machine body and provided with a loop-taker body and a loop-taker tip co-operating with the needle of the sewing machine, characterized in that the loop-taker tip (10) is a part of an arm, a slide or the like (9) journalled in the loop-taker body (1), and that guiding means (6, 8, 15) are disposed for adjusting the loop-taker tip in relation to the needle (12) in different zig-zag positions of the needle.

2. A loop-taker of a sewing machine according to Claim 1, characterized in that the loop-taker body is provided with a circular bearing surface (22) and a groove (18) through the wall of the bearing, the loop-taker tip projecting into said groove.

3. A loop-taker of a sewing machine according to Claim 2, characterized in that the loop-taker body has a slot (20) below the bearing surface (22) constituting a guideway for the arm.

4. A loop-taker of a sewing machine according to Claim 2, characterized in that next to the loop-taker tip on the arm a needle guide (11) is located which also projects into a slot (19) and separates the tip from contact with the needle.

5. A loop-taker of a sewing machine according to Claim 1, characterized in that said guiding means is constituted of a cam (6) provided on said loop-taker shaft (3) and a cam follower (8), co-operating with the cam and provided on the said arm (9) and an elastic member (15) for pressing the follower against the cam.

6. A loop-taker of a sewing machine according to Claim 4, characterized in that the masses of the loop-taker tip and the needle guide and their distances from the loop-taker shaft are determined to give an increased pressure of the cam follower against the cam at a high r.p.m. of the loop-taker body.