EP0061184B1 - Method of making sewing-machine needles - Google Patents

Description

The invention relates to a method for producing sewing machine needles from a cylindrical wire section by compression molding, in which, starting from a wire section diameter corresponding to the thickness of the needle piston, the wire section is reduced over at least the length of the needle shaft and the shoulder to approximately its end cross section and in which, in the region of the needle shaft, needle or thread channels are pressed in from the curved lateral surfaces of the wire section to produce a flattening, the lateral extension of which is reduced in a subsequent step.

A method which replaces the classic reduction method by means of a circulation press (DE-A-1 952 152) has been proposed by CH-A-302 627. There, the wire section in the area of the needle shaft and attachment to be formed is first pressed flat to the cross-sectional thickness of the needle shaft. After this flattening and pressing of the needle or thread channels, the lateral flattening residues are removed down to the cross-sectional dimension of the shaft, using cutting tools. This takes place, starting from the tip end of the blank, in a time-consuming milling stroke that extends over the entire length of the shaft. The latter is tool-intensive and also technically difficult, since the small needle body can hardly be mastered in the required manner and, for example, can be clamped without leaving printing marks. On the other hand, it is known, for example from US-A-4 037 641, to press the eye of the needle to form a beard and to separate the beard while still piercing the ear. The stock is reduced by means of a circulation press.

The object of the invention is to provide an optimal needle manufacturing method which manages with a simple tool with only a fraction of the stroke distance and thus achieves a high degree of economy.

This object is achieved by the method steps specified in claim 1.

The subclaims are measures of advantageous further developments.

As a result of such a configuration, an economical, extremely economical machine needle manufacturing process is achieved: the reduction in diameter of the initial cross-section up to the final diameter of the needle shaft, the shoulder and the tip contour takes place with the formation of lateral surfaces which already have the final diameter and the shape of the parts mentioned. The excess material that is displaced in the process merges into opposite, laterally protruding flat beards of this lateral surface. The entire raw shape of the needle can be produced with an extremely short press stroke. The blank material that is displaced during the simultaneous guttering also travels in the shortest possible direction towards the flat beards when the needle gutters are pressed. The routing, which usually runs right into the eye area, provides an advantageous centering for the protrusion of the tool which punches the eye of the needle. The separation of the flat beards can occur when punching the eye of the needle, i.e. H. in the punching end phase. Using one and the same press stroke, it is favorable to carry out the cross-sectional profiling of the piston when pressing the flat beards. The beards that arise on both sides of the blank axis can be used in a favorable manner as a guiding and holding surface in connection with the individual process steps. The basically very small blank can be mastered well using this fact. The basic shape is roughly boat-shaped. The fillet between the two diametrically opposite, convex lateral surfaces and the subsequent broad beard surface also offers a favorable, self-centering cutting edge orientation. The shaft cross-section is not supported in the area of the radial flow direction of the flat whiskers by the shaping upper and lower die part, so that there is an adapted free exit of the excess material. This also prevents stresses in the material. The axial stretching accuracy is optimal. The tip area of the needles surrounded by flat beards is stabilized. In addition, the tip area can be safely grasped, determined and controlled. The intermediate section between the beards provides enough space for the provision of a fitting hole for interaction with a dowel pin located on the tool. A sequence of steps that is particularly gentle on the material and tools is given if, after separating the flat beards when pressing the eye section and pre-pressing the needle tip when pressing the eye section and pre-pressing the needle tip and pressing the needle shaft groove, the tip side again protrudes sideways End area lying beard-like approaches are pre-pressed, which adjoin the intermediate section, a throat is further formed, whereupon the blank receives its needle eye, after which it is countersunk from this side and then turned over in the pressing tool in order to sink the needle eye on the on the other side, which is followed by pressing and trimming the tip, and then severing the lugs together with the intermediate section. The intermediate section formed by the flat beards is also useful for turning over the blank.

The flat whiskers can also be used in a cost-effective way to achieve high resistance to bending load forces acting on the needle shaft. The transition area between shoulder and shaft is particularly prone to breakage. In this regard, there will be ago proposed that two diametrically opposed wings are provided in the transition area between the neck and needle shaft, which remain as beard sections when the flat beards are separated. Furthermore, it is advantageous if the back of the wing is convex, the plane of the wing lies transversely to the direction of the eye of the needle and the wing extends over the full length of the shoulder and to approximately the same extent over the initial length of the needle shaft. The wings always fall due to the material, which is always smaller in cross-section. The notch zone, which forms a possible breaking point, even if it is very obtuse, between the frustoconical taper of the shoulder and the shaft is highly stabilized by the wings. The latter act as stiffening ribs. Due to their diametrical arrangement, they are also far enough away from any piston flattening provided in household sewing machine needles. They can also be produced with sufficient material thickness. When aligned parallel to the flattening mentioned, the wings also do not stand in the way, since they do not protrude above them; the marking of such flats can therefore always be carried out without hindrance. The measure that the back of the wings formed by the flat beard remains curved convexly prevents protruding injuries or hooking with the textile material. In addition to the back curvature, the outer wing edges and inside corners can be rounded transversely. Taking into account the direction of loading when sewing, it is advantageous that the plane of the wings is transverse to the direction of the eye of the needle. Optimal stability results in a simple manner in that the wings extend over the full length of the extension and to approximately the same extent over the initial length of the needle shaft.

• Fig. 1 den das Ausgangsmaterial bildenden Drahtabschnitt von der Länge gleich zweier Nadeln in Seitenansicht, und zwar in vergrößertem Maßstab,
• Fig. 2 den Rohling nach dem Pressen,
• Fig. 3 den Rohling nach Abtrennen der Flach-Bärte und Stanzen des Nadelöhrs,
• Fig. 4 den Schnitt gemäß Linie IV-IV in Fig. 3,
• Fig. 5 den Schnitt gemäß der Linie V-V in Fig. 1, und zwar in gegenüber Fig. 1 weiter vergrößertem Maßstab,
• Fig. 6 den Schnitt gemäß Linie VI-VI in Fig. 2, und zwar mit Ober- und Untermatrize,
• Fig. einen Schnitt durch das Abtrennwerkzeug vor Durchführung der Bart-Abtrennung und dem Stanzen des Nadelöhrs,
• Fig. 8 einen abgelängten Drahtabschnitt in Seitenansicht auch wieder von solcher Länge, die es ermöglicht, gleichzeitig zwei Nadeln herzustellen, und zwar unter Anwendung einer mehr aufgeteilten Schrittfolge des Verfahrens,
• Fig. 9 den Rohling nach dem Flachpressen des Kolbens als vorgezogene Wah)maßnahf_HR.
• Fig. 10 den Rohling nach dem Formpressen des Ansatzes und Nadelschafts der Doppelnadel,
• Fig. 11 denselben nach dem Beschneiden unter Belassen eines Flach-Bart-Restabschnitts als Zwischenabschnitt zwischen den gegeneinanderweisenden spitzenseitigen Enden der Doppeinadel,
• Fig. 12 den Rohling nach dem Formpressen der langen Rinne samt Öhrpartie und dem Vorpressen der Nadelspitze,
• Fig. 13 die Unteransicht hierzu unter Verdeutlichung der dabei miterzeugten Hohlkehle,
• Fig. 14 den Rohling in Darstellung wie Fig. 12, jedoch nach dem Lochen,
• Fig. 15 den Rohling nach dem Einsenken (Verrunden des Loches) von der einen Seite her,
• Fig. 16 den Rohling nach dem Umwenden und Einsenken von der anderen Seite her,
• Fig. 17 den Rohling nach dem Beschneiden der Spitzen,
• Fig. 18 denselben nach dem Pressen der Spitzen und Trennen der beiden Nadeln voneinander,
• Fig. 19 den Schnitt gemäß Linie XIX-XIX in Fig. 8, und zwar in gegenüber Fig. 8 weiter vergrößertem Maßstab,
• Fig. 20 den Schnitt gemäß Linie XX-XX in Fig. 9,
• Fig. 21 den Schnitt gemäß Linie XXI-XXI in Fig. 10,
• Fig. 22 den Schnitt gemäß Linie XXII-XXII in Fig. 11,
• Fig. 23 den Schnitt gemäß Linie XXIII-XXIII in Fig. 12,
• Fig. 24 den Schnitt gemäß Linie XXIX-XXIX in Fig. 12,
• Fig. 25 die Nähmaschinennadel nach Abtrennen der Flach-Bärte bis auf flügelbildende Bartabschnitte im Bereich des Ansatzes,
• Fig. 26 diese Nadel in Seitenansicht und
• Fig. 27 den Schnitt gemäß Linie XXVII-XXVII in Fig. 25 in weiter vergrößertem Maßstab.

Further advantages and details of the subject matter of the invention are explained in more detail below with reference to exemplary embodiments illustrated in the drawings. It shows

• 1 is a side view of the wire section forming the starting material, the length of two needles, to be precise on an enlarged scale,
• 2 shows the blank after pressing,
• 3 shows the blank after separating the flat beards and punching the eye of the needle,
• 4 shows the section along line IV-IV in FIG. 3,
• 5 shows the section along the line VV in Fig. 1, namely on a larger scale compared to FIG. 1,
• 6 shows the section along line VI-VI in FIG. 2, with an upper and lower die,
• 1 shows a section through the severing tool before performing the beard severing and punching the eye of the needle,
• 8 shows a cut wire section in side view again of such length that it is possible to produce two needles simultaneously, using a more divided step sequence of the method,
• Fig. 9 the blank after pressing the piston flat as an advanced wah) measure _HR .
• 10 the blank after compression molding of the neck and needle shaft of the double needle,
• 11 the same after trimming while leaving a flat beard remaining section as an intermediate section between the opposing tip-side ends of the double needle,
• 12 the blank after the long channel including the eye portion has been compression-molded and the needle tip has been pre-pressed,
• 13 shows the bottom view for this purpose, clarifying the groove which is also produced in the process,
• 14 shows the blank in a representation like FIG. 12, but after punching,
• 15 the blank after sinking (rounding the hole) from one side,
• 16 the blank after turning and sinking from the other side,
• 17 the blank after trimming the tips,
• 18 the same after pressing the tips and separating the two needles from each other,
• 19 shows the section according to line XIX-XIX in FIG. 8, specifically on an enlarged scale compared to FIG. 8,
• 20 shows the section along line XX-XX in FIG. 9,
• 21 shows the section along line XXI-XXI in FIG. 10,
• 22 shows the section along line XXII-XXII in FIG. 11,
• 23 shows the section along line XXIII-XXIII in FIG. 12,
• 24 shows the section along line XXIX-XXIX in FIG. 12,
• 25 the sewing machine needle after severing the flat beards except for wing-forming beard sections in the area of the attachment,
• Fig. 26 this needle in side view
• Fig. 27 shows the section along line XXVII-XXVII in Fig. 25 in a further enlarged scale.

The blank for sewing machine needle manufacture is formed by a wire section A cut to length. This has a circular cross-section. Its diameter corresponds approximately to that of the cylindrical needle piston 1. Both ends of the wire section are chamfered at 1 '. The total length of this wire section A corresponds to the material requirement for the simultaneous production of two sewing machine needles. This wire section A is placed in a pressing tool, the upper die with 2 and the lower die with 3 is designated. The tool is equipped in such a way that, in addition to punching the eye section Ö, the final needle shape is produced with a press stroke by reducing the cross-section. The blank then has the usual flattening 4 in the area of its piston 1 and the adjoining truncated cone Appropriate approach 5. The latter merges into the needle shaft 6, which ends in a needle tip 7. The usual fillet 6 'is also taken into account on the piston side of the eye section.

The needle shaft 6 takes the form of a V-profile as a result of the simultaneous pressing in of a needle groove 8 extending from the shoulder 5 to the tip region.

The blank material displaced due to the reduction in cross-section and channel formation emerges through a tool gap Sp left on both sides between the upper and lower dies 2, 3. The flat beards that form are designated by 9. Their width depends on the displacement volume. Less material is displaced in the area of the neck 5 than in the tip area.

The flat beards 9 bring a flat strip-like width enlargement of the blank which is advantageous for the next method step; it is many times larger in area and can therefore be gripped better and brought into the next tool station and centered there in position 10. During the punching, the blank is held on its flat beards 9 between the jaws of a separating device V. The needle shaft 6 itself lies in a lower punch 11 with a perforated window 12. The associated upper punch 13 has a punching projection 14. The punching projection 14 runs from above into the centering groove 8 which is V-shaped in cross-section and rounded in its V-apex. Immediately after the punching of the needle eye 10, the two flat beards 9 are cut off at the same time, in the present case sheared off by the jaws of the separation device V then being carried along by the upper punch moving downward relative to the lower punch 11 which remains. The corresponding time delay is achieved by switching on a free passage X between the upper punch 13 and the upper jaw of the separating device. Only when the two shoulders 15 located to the side of the punching projection, offset in height from it, step onto the corresponding shoulders 16 of the upper jaw of the separating device, are the jaws acting as scissors displaced in the sense of separating the flat beards 9.

The upper punch 13 can be held high by springs. The springs are not shown in detail.

In the separating device V, the ear edges can already be rounded.

After rounding the eye edges, the tip 7 takes on its final shape, either as a rounded tip or as a pointed tip. After finishing, the usual treatment phases follow, such as heat treatment, polishing, galvanizing and finally the final inspection.

In the method or exemplary embodiment that follows, the formation of two sewing machine needles is divided into a larger sequence of steps. The pistons 1 are left or formed in a first station of a clock-controlled follow-up tool at the free ends of the wire section A. In the case of the production of a flat piston, the piston-forming end region is correspondingly provided with a flat 4 (FIG. 9). Along with this, a marking or indication of origin can already be made by means of embossing.

The blank reaches the second station from the first station in which the flattening 4 is produced (FIG. 10). Here, again, the compression molding takes place in such a way that the displaced material in the area of the extension 5 and the needle shaft 6 to be formed diverts into the joint between the upper and lower dies of the tool (not shown here). By pressing the resulting reduction in cross-section on the two opposite wire material cross-sections creates the laterally protruding flat beards 9, which freely project from the circular needle shaft and shoulder cross-section formed as joints. Reference is made to the sectional illustration in FIG. 21.

The approach 5 has the shape of a truncated cone. The wider base faces the piston 1. The illustration in FIG. 10 already shows, as far as the extension 5 and shaft 6 are concerned, the final contour like a relief of the needles to be formed. The diametrically rooted flat whiskers 9 allow the transversely convex lateral surfaces M of extension 5 and shaft 6 to stand between them.

The blank is now trimmed in the third station (FIG. 11). The shaft 6 is given the cross-sectional shape according to FIG. 22. The flat, vertical separating cut surfaces are pressed into a curve during channel pressing if this is provided in terms of shape (free spaces in the die). The trimming is carried out in such a way that the flat whiskers 9 are removed or severed over a length section which corresponds approximately to that of the end length of the needle shaft 6, except for an intermediate section 9 'which is beyond the needle tips 7 to be formed. As a result, two diametrically opposed wings F remain as material residue, which, like the previously formed mustaches 9, extend parallel to the flattening 4. The remaining intermediate section 9 'has the shape of a rectangular plate with the longer side oriented transversely to the blank axis. Its edge 9 "can be used to limit the stop.

In the subsequent station four (FIG. 12), the long needle groove 8, the eye portion Ö extending from the attachment 5 to the tip region, and the pre-pressing of the tip 7 to be formed are molded. The shaft 6 of the sewing machine needle takes the shape shown in FIG. 23 shown truncated V-shaped cross-sectional shape. However, other cross-sectional shapes can also be achieved, round, square, polygon etc. The needle groove 8 is symmetrical. The V-tip, like the V-leg ends, is convexly rounded. The channel bottom, on the other hand, has a concave shape rounding up, which essentially corresponds to the thread cross-section. Material is again displaced when pressing the eye section Ö and pre-pressing the needle tip. Both in the area of the needle groove 8 on the eye side and in the tip-side end area, wing-like projections 9 "'projecting sideways on both sides, which together have approximately the outline of a sound body of known stringed instruments, the larger belly section being directly adjacent to the remaining intermediate section 9', ie immediately adjoins this.

The tip-forming part of compression molding here consists in cutting off the tip area, starting from the general shaft diameter. This creates a roof-shaped, wedge-shaped bevel Sch, which slopes down on both sides to the level of the intermediate section 9 'which is also further flattened and remains. During this pressing process, the circular needle shaft section 6 "disappears there. The intermediate piece 9 'widens somewhat as a result. The intermediate piece 9', which is now completely flattened, can have a fitting hole L as a centering aid or additional alignment aid for the edge edges 9" (FIG. 12, dot-dash line) Circle), which interacts with a dowel pin of the tool.

As can be seen from the inverted blank in FIG. 13, the so-called fillet 6 ′, which extends on the side of the needle shaft 6 opposite the needle groove 8, has already been pressed in the area of the eye area Ö. This also includes the simultaneous formation of the short channel 17. The eye itself is not yet perforated. It is only pre-embossed and already marked as a bottleneck with 10 in FIGS. 12 and 13 for easier understanding. The depth of the embossings is indicated in FIG. 24 by the lines 10 ′ and 10 ″ reproducing the embossing reason at this stage.

The hole in the eye 10 is only punched in the fifth station of the tool (FIG. 14). Here the ear-forming area is completely pierced. This can be done extremely precisely, since the entire tip area can be positioned and held firmly by the remaining intermediate section 9 'of the flat beards 9 and also by the additional lugs 9 ". In addition, the crosswise to the perforation direction on the side flanks of the Needle shaft standing approaches 9 '"practically form a kind of lateral stabilizing rib, which effectively prevent an unwanted change in shape in the area of the ear area.

In the next station, the sixth, the eye is lowered from one side of the needle (Fig. 15). In the seventh station (FIG. 16) the sinking takes place from the other side. Sinking is to be understood as the so-called rounding of the edges R of the eye hole which have a sharp ridge.

The blank then comes to the eighth station. This station (Fig. 17) is reserved for trimming the tip 7. The tip is already flattened on both sides in the plane of the V-axis. In the trimming which now takes place in FIG. 17, a flattening which is also roof-shaped or wedge-shaped is cut perpendicular to it. The cutting lines are designated 7 '. A kind of pyramid tip with a square outline or cross section is achieved. The waste piece shown in FIG. 17, consisting of the intermediate piece 9 'and, if appropriate, the lugs 9 "', is shown in dash-dotted lines.

In the subsequent ninth station (Fig. 18) the final individual compression molding of the tip is effected. The area previously occupied by the intermediate section 9 'is available for the further tapering of the tip. The waste contour of said intermediate section 9 'is again indicated here in dash-dotted lines.

The blank produced - taking into account the double-needle manufacturing process in the manner described there are two blanks - is passed on for further treatment, such as heat treatment, surface grinding, nickel plating, final search and straightening.

Leaving a remaining section of the flat whiskers 9 that remains in the area of the needle tip 7, in cooperation with the approaches 9 ″ ′, which has been added in the process, has proven to be an advantageous stabilization of the basically weakest section of the needle body Loches, as already mentioned, enables extremely precise production, and this flattened section, which also serves as an orientation and turning aid, can also be used as a material bridge in the area of the opposing tips of a double needle, which creates the best manufacturing conditions in machines, even with high needle throughput.

The intermediate product shown in FIGS. 2, 6 and 10, 21 has two lateral surfaces M of a core cross-section K (approximately shaft or shoulder cross-section) lying approximately in the nominal dimension of the needle shaft 6, mirror-inverted opposite one another, of which the laterally protruding flat whiskers 9 going out. Their total material cross-section B1 and B2 corresponds to the difference between the piston cross-section Q (Fig. 19) and the core cross-section K.

The transverse displacement of the materials can be driven so far that practically 90% of the needle surface - distributed over the top and bottom of the blank - is available as a finished final shape through a press stroke.

The explained flat beard formation by compression molding offers further advantageous possibilities. With reference to FIGS. 25-27, two diametrically opposed vanes F ', which extend in the longitudinal direction of the needle blank, are left in the transition region between attachment 5 and needle shaft 6. When the flat beards 9 are separated, this is how it is done proceeded that the wings F 'remain as beard sections. The plane EE of the wings F 'lies parallel to the flattening 4 of the piston 1 and transversely to the direction of insertion of the needle eye 10.

The wings F 'are cut free so that they extend to form a stabilizing rib over the full length y of the extension 5 and to approximately the same extent over the initial length z of the needle shaft 6. The length z corresponds approximately to twice the shaft diameter.

The back 18 of the wings F 'is convexly curved, in such a way that the greatest rib width is in the area of the angular groove K between the needle shaft 6 and the shoulder 5. The curvature is even; the back ends merge into the shaft 6 or the piston 1 at an obtuse angle. This prevents any entanglement zones. The area width or size of both wings F 'together corresponds approximately to the area dimension of the flat 4. The thickness of the wings corresponds to approximately half the needle shaft diameter, but at least one third of this diameter.

Claims (6)

1. A method of production of sewing-machine needles from a cylindrical section (A) of wire by die stamping, in which when starting out from a diameter of the section of wire corresponding with the thickness of the butt (1) of the needle the section of wire is reduced over at least the length of the shank (6) of the needle and of the shoulder (5) to about its final cross-section, and in which in the region of the shank of the needle needle gutters or thread gutters (8, 17) are stamped in from the curved surface of the section of wire whilst creating a flattening which in a succeeding step is reduced in its lateral extent, characterized in that during stamping there is stamped simultaneously a reduction in diameter from the initial crosssection to the final diameter of the needle shank (6) and of the shoulder (5) and the contour of the tip respectively, in doing which surfaces (M) are formed, which already have the final diameter of the needle shank (6) and the shoulder (5) and the tip contour respectively, and in doing which the severing of the flattening projecting from these surfaces (M) as flat burrs (9, 9) on opposite sides is effected by stamping.

2. A method as in Claim 1, characterized in that the stamping of the needle gutters (8, 17) is effected together with the stamping of the flat burrs (9).

3. A method as in Claim 1, characterized in that during stamping of the flat burrs (9) a profiling of the cross-section of the butt (1) is being stamped at the same time.

4. A method as inClaims 1 or 3, characterized in that after the severing of the flat burrs (9) during stamping of the eye portion (Ö) and after the rough-stamping to shape of the tip (7) of the needle and the stamping of the gutter (8) in the needle shank, sideways projecting burrlike extensions (9"') lying in the end region next the tip are rough-stamped anew, which are connected to the intermediate section (9'), and further a throat (6') is formed, whereupon the blank obtains its eye (10) (piercing), according to which sinking is effected from the near side and subsequent turning round of the blank in the press tool (Fig. 14) in order to effect sinking of the needle's eye (10) on the other side, subsequent to which the stamping and trimming of the tip (7) is effected, and further the severing of the extensions (9"') together with the intermediate section (9').

5. A method as in Claim 1, characterized in that in the region of transition between the shoulder (5) and the shank (6) of the needle two wings (F') lying diametrically opposite one another are provided, which remain as sections of burr upon severing of the flat burrs (9).

6. A method as in Claim 5, characterized in that the ridge (18) of the wings (F') has a convex curvature, the plane (E-E) of the wings (F') lies transversely to the direction of piercing of the eye of the needle and the wings (F') extend over the full length (y) of the shoulder (5) and for about an equal distance along the initial length (z) of the needle shank (6).

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