Sewing – Elements – Needles
Reexamination Certificate
2001-02-23
2001-11-20
Izaguirre, Ismael (Department: 3765)
Sewing
Elements
Needles
Reexamination Certificate
active
06318281
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 100 08 447.8 filed Feb. 23, 2000, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a sewing machine needle.
Generally, sewing machines have a needle which, in the vicinity of its point, has an eye through which an upper thread is guided. During sewing, the needle pierces through the material to be sewn (flat textile fabric) and, as a result of a stepwise feed of the fabric, the needle produces spaced stitch holes. The upper thread is guided from stitch hole to stitch hole, and during this occurrence the thread glides over an edge of the eye both in the forward and in the reverse direction. When the feed direction of the fabric is determined, the needle has a fixed working direction and the fabric is advanced in a fixed direction which, as a rule, is oriented transversely to the eye.
It has been found, however, that in sewing machines which provide for a fabric feed in different directions, for example, in forward and rearward directions or in several other directions, the seam quality depends from the sewing direction and/or the thread twist. Such a dependence is often not desirable.
German Utility Model 86 32 106.4 discloses a tufting needle which has, in the direction of the needle axis, an elongated eye provided at both ends with respective curved upper and lower eye edges. At the outlet side the eye edge is straight. The tufting needle is of asymmetrical construction as seen in top plan view, that is, in the direction of the eye axis. On the outlet side the eye adjoins a curved thread trough. A tufting needle of this type has a preferred working direction.
In contrast, U.S. Pat. No. 3,986,468 discloses a symmetrical needle for a sewing machine. In the vicinity of its point, the needle has an eye extending transversely through the needle body and bounded by two eye walls. Both eye walls have straight edges at their upper as well as at their lower sides, that is, the edges of the side walls extend in each instance along a straight line from the eye end oriented toward the needle shank (clamping portion) to the eye end oriented toward the needle point. Although such needles are of symmetrical construction, they have a different behavior for a forward sewing and a reverse sewing with twisted threads.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved sewing machine needle of the above-outlined type which reduces quality differences between seams made in different sewing directions.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the sewing machine needle includes a blade; a shank extending from one blade end and adapted to be clamped in a sewing machine; a needle point provided at the other blade end; an elevation provided on the blade adjacent the needle point; and an eye traversing the blade adjacent the needle point. The eye has a first eye end oriented toward the shank; a second eye end oriented toward the said point; a thread inlet side; and a thread outlet side. The elevation is situated on the thread outlet side between the needle point and the second eye end. The eye is bordered by two facing eye walls each having a respective edge at the thread outlet side. Each edge extends from the first eye end to the second eye end such that it is recessed from an imaginary straight line connecting the second eye end with the elevation.
The needle according to the invention has an eye which extends transversely through the needle body. By “transversely” there is meant a perpendicular orientation of the eye to the longitudinal central axis of the needle body or an inclined orientation at an obtuse angle thereto. The needle eye is bounded by two eye walls which are recessed at the outlet side of the eye, that is, at the side from which the thread extends to the fabric. Stated differently, the eye wall edges are curving towards the needle back or are otherwise shaped. The eye walls which may continue as side walls of a thread outlet trough, extend thus between two locations which, with respect to the needle thickness, each have a local elevation. In this manner the recessed eye walls make possible for a twisted thread to run transversely to the eye, laterally over the eye wall without appreciably changing the twist of the thread as it runs over the eye wall. By virtue of the diminished interference with the thread twist a basic condition is provided for the purpose that in the different sewing directions the seams have at least approximately the same quality. Thus, for example, the thread has no appreciably different twist as it traverses the eye walls irrespective of whether forward or reverse sewing is performed.
By recessing the contour in the region of the eye below an imaginary connecting line between the shank-side eye end and an adjoining, needle point-side elevation, the friction between the thread and the edge of the eye wall is reduced. The reduction of the friction thus has a lesser effect on the thread, independently from the angle which is formed between the thread and the needle. Accordingly, the thread will be less twisted or untwisted and thus an improved seam formation and an improved quality of the sewn fabric are ensured. Further, effects appearing in extreme cases in conventional needles are avoided. If, during sewing, the twist of a twisted thread is excessively affected, the loop formation may be adversely influenced. In case a thread is untwisted or additionally twisted and is, in such a condition, pulled through the fabric, upon withdrawing the needle it may turn or curl without forming a required, regular loop. Such an occurrence results in defective stitches and may also lead to thread breakage. By virtue of the new needle contour according to the invention, such extreme defects may be avoided. This applies particularly to multidirectional sewing in which the fabric may be automatically advanced in all (but at least, in two) directions.
The effect of the lesser influence of the thread twist in a needle according to the invention may also have significance in sewing machines which sew merely in a single direction. The needle according to the invention permits the use of upper threads having different twists, for example, right-hand twists or left-hand twists, wherein the effect of the twist direction has a significantly reduced effect on the seam quality and becomes insignificant in most cases.
The eye walls are preferably of stepless course, and the outlet side of the eye is concavely curved. Such a curved construction of the upper edges of the eye walls at the outlet side supports the above-noted uniform thread run independently from the sewing direction and furthermore, it permits a high sewing speed because of the overall reduced eye height which results in a slow opening of the stitch hole.
In a preferred embodiment of the invention a thread trough is provided which adjoins the outlet end of the eye and which extends in the direction of the needle point. The eye walls continue as the side walls of the thread trough. In this manner a very satisfactory thread guidance is achieved and, in particular, a good support of the thread during loop formation is obtained. Loop formation occurs at the moment the needle has pulled the thread through the fabric and begins, or is in the process of performing, its reverse stroke.
A concave, arcuate curvature of the side walls makes possible a general rounding of the side wall edge or its flattening transversely to the orientation of the needle eye. In either case, the thread may run substantially undisturbed over the respective edge and the angle which the individual strands or filaments of the thread form with the eye wall is of subordinated significance. This applies particularly to a construction having a flattened edge.
According to an advantageous embodiment of the invention, the thread trough at the outlet side of the needle eye is oriented
Hillenbrand Bernd
Horn Gerd
Groz-Beckert KG
Izaguirre Ismael
Kelemen Gabor J.
Venable
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