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(11) | EP 0 090 544 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
An outer shuttle for a sewing machine and process of making same Greife und Verfahren zu dessen Herstellung Boucleur et procédé pour le fabriquer |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to a process for manufacturing an outer shuttle, for a full rotary shuttle, for use in a sewing machine, and to an outer shuttle as such.
[0002] Generally, it is known that during regular operation of a sewing machine, the needle moves up and down and may contact the cone point provided on the outer shuttle for catching thread. When this happens, the cone point can be damaged or deformed, leading to stitches being missed and thread breakage troubles being induced. Previously, in order to solve the problem, the cone point, which is made of a piece of sintered hard alloy, was connected to a main body of the outer shuttle by brazing. One of the problems arising, however, is that the use of this additional part significantly increases the overall cost and complexity of machining, since the sintered alloy is extremely hard. It follows that, as a result of the connection by brazing, the reliability and strength of the contact face between the outer shuttle main body and the cone point decreases.
[0004] According to the present invention there is provided a process for manufacturing an outer shuttle for use in a sewing machine, characterised by the steps of: providing an outer shuttle main body; building up a projection by welding, on a portion of the outer shuttle main body where a cone point is to be formed; and machining the welded built up projection to form the cone point.
[0005] The present invention also provides a shuttle for use in a sewing machine having an outer main body, and a projection built up by welding on a portion thereof and machined to form a cone point.
[0006] The built up welding is preferably by plasma arc welding, and the outer shuttle main body can be made of case hardened steel.
[0007] Preferably, martensitic high chromium steel is used to build up the projection on an outer shuttle main body, whereon the built up welded portion is machined so as to form an accurate and hard cone point. The cone point has excellent impact resistance and abrasion resistance, and damage and deformation of the cone point caused by contact with a needle is generally avoided. Also, defects such as stitch skipping and thread breakage are less likely. Accordingly, with the invention, manufacturing is easy and gives a sufficient strength to the connection between the outer shuttle main body and the cone point.
[0008] In order that the invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings, in which:
Fig. 1 is a side view of a shuttle of the present invention, and
Fig. 2 is a schematic illustration showing the process of manufacturing the cone point of the outer shuttle thereof.
[0009] Fig. 1 shows a side view of a vertical full rotary shuttle embodying the present invention. On an outer shuttle 1, a boss 2 is provided which is driven rotatably about an axis 10. The outer shuttle 1 is provided with an inner shuttle 3. The outer shuttle 1 is also built up to have a crochet needle 4. At the tip of this crochet needle 4, a cone point 5 is formed. A spring 6 is screwed on the outer shuttle 1 and fixed firmly.
[0010] Referring now to Fig. 2, the manufacturing process of the cone point 5 is explained. The outer shuttle main body including the crochet needle 4, boss 2 and other small parts is made of a case hardened steel such as case hardened carbon steel or case hardened chrome molybdenum steel, and is formed by means of a precision casting, precision forging, machining or another suitable method. The outer shuttle main body may be fabricated using the same materials except for case hardened steel. Referring to Fig. 2(1), the tip of the crochet needle 4 on which the cone point 5 is to be provided is formed by means of machining or other process. As shown in Fig. 2(2), a strip of martensitic high chromium steel is used to perform built up welding by means of an electrode 8 at a portion where the cone point 5 is to be formed as a hardened cone point. This built up welding is carried out by means of a plasma arc welding process. According to this process, built up welding can be conducted successfully using a minimum amount of the martensitic high chromium steel welded to the case hardened steel which forms the outer shuttle main body.
[0011] The numeral 9 denotes the built up welded position formed by the welding procedure. The built up welding 9 is then machined and formed into a precise cone point 5 as shown in Fig. 2(3). The outer shuttle 1 thus formed together with the cone point 5 is then further hardened by means of a heat treatment such as a quench hardening.
[0012] In general, when martensitic high chromium steel is rapidly cooled down from the austenitic state to a lower temperature, a martensitic hardening is produced in the internal steel structure, so that appropriate hardness can be given to the cone point 5. Furthermore, tempering the martensitic hardened portion mentioned above is preferred, which imparts toughness to it. As a result, the cone point 5 is provided with both excellent impact resistance and abrasion resistance. In addition, it is advantageous that the martensitic high chromium steel has good plasticity in cold forming processes, such as the machining process in which the built up welding portion 9 is machined and formed into the cone point 5. Further, the welding procedure in which the built up welding portion 9 will be made is also simplified.
1. A process for manufacturing an outer shuttle (1) for use in a sewing machine, characterised
by the steps of: providing an outer shuttie main body; building up a projection (9)
by welding, on a portion of the outer shuttle main body where a cone point (5) is
to be formed; and machining the welded built up projection (9) to form the cone point
(5).
2. A process according to claim 1, characterised in that the method of welding is
plasma arc welding.
3. A process according to claim 1 or 2, characterised in that the outer shuttle main
body is made of case hardened steel.
4. A process according to claim 1, 2 or 3, characterised in that the projection is
of martensitic high chrome steel.
5. A process according to claim 4, characterised in that the projection is tempered
prior to machining.
6. A shuttle for use in a sewing machine having an outer main body, and a projection
(9) built up by welding on a portion thereof and machined to form a cone point (5).
7. A shuttle according to claim 6, characterised in that the outer shuttle main body
is made of case hardened steel.
8. A shuttle according to claim 6 or 7, characterised in that the projection is of
martensitic high chrome steel.
9. A shuttle according to claim 8, characterised in that the projection is tempered.
10. A sewing machine provided with a shuttle according to any one of claims 6 to 9
or made according to the method of any one of claims 1 to 5.
1. Verfahren zur Herstellung eines Greifers (1 ) zur Verwendung in einer Nähmaschine,
gekennzeichnet durch folgende Schritte: Schaffung eines Hauptkörpers für den Greifer,
Aufschweissen eines Vorsprungs (9) an einem Abschnitt des Hauptkörpers des Greifers,
auf dem eine Kegelspitze (5) gebildet werden soll, und Bearbeitung des aufgeschweissten
Vorsprungs (9) zur Ausbildung der Kegelspitze (5).
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass das Schweissverfahren ein
Plasmabogenschweissverfahren ist.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass der Hauptkörper
des Greifers aus einsatzgehärtetem Stahl hergestellt wird.
4. Verfahren nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, dass der Vorsprung
(9) aus martensitischem Hoch-Chromstahl besteht.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass der Vorsprung (9) vor der
Bearbeitung getempert wird.
6. Greifer zur Verwendung in einer Nähmaschine, gekennzeichnet durch einen Hauptkörper
und einen Vorsprung (9), der an einem Abschnitt des Hauptkörpers aufgeschweisst und
zur Ausbildung einer Kegelspitze (5) bearbeitet ist.
7. Greifer nach Anspruch 6, dadurch gekennzeichnet, dass der Hauptkörper des Greifers
aus einsatzgehärtetem Stahl besteht.
8. Greifer nach Anspruch 6 oder 7, dadurch gekennzeichnet, dass der Vorsprung (9)
aus martensitischem Hoch-Chromstahl besteht.
9. Greifer nach Anspruch 8, dadurch gekennzeichnet, dass der Vorsprung (9) getempert
ist.
10. Nähmaschine mit einem Greifer nach einem der Ansprüche 6 bis 9, oder die gemäss
dem Verfahren nach einem der Ansprüche 1 bis 5 hergestellt ist.
1. Procédé pour fabriquer un boucleur extérieur (1 ) utilisable dans une machine à
coudre, caractérisé par les mesures consistant à: prévoir un corps principal de boucleur;
réaliser une saillie (9) par soudage, sur une portion du corps principal du boucleur
où une pointe conique (5) doit être formée; et usiner la saillie (9) soudée ainsi
réalisée pour former la pointe conique (5).
2. Procédé selon la revendication 1, caractérisé en ce que le procédé de soudage est
un soudage au plasma d'arc.
3. Procédé selon la revendication 1 ou 2, caractérisé en ce que le corps principal
de boudeur est formé d'acier cémenté.
4. Procédé selon l'une des revendications 1, 2 ou 3, caractérisé en ce que la saillie
est formée d'acier martensitique à teneur élevée en chrome.
5. Procédé selon la revendication 4, caractérisé en ce que la saillie est trempée
avant usinage.
6. Boudeur utilisable dans une machine à coudre, comprenant un corps principal extérieur,
et une saillie (9) réalisée par soudage sur une portion de celui-ci et usinée pour
former une pointe conique (5).
7. Boucleur selon la revendication 6, caractérisé en ce que le corps principal du
boudeur est formé d'acier cémenté.
8. Boucleur selon la revendication 6 ou 7, caractérisé en ce que la saillie est formée
d'acier martensitique à teneur élevée en chrome.
9. Boucleur selon la revendication 8, caractérisé en ce que la saillie est trempée.
10. Machine à coudre munie d'un boucleur selon l'une des revendications 6 à 9 ou réalisée
conformément au procédé de l'une des revendications 1 à 5.