US1949350A - Method of making sewing machine needles - Google Patents

Description

Feb. 27, 1934. E. K. BROWN 1,949,350

METHOD OF MAKING SEWING MACHINE NEEDLES Original Filed Jan. 12, 1953 Jfl' ll MW M 2 EJZmaRcZATBI-Oww 7 I; I 4,

Patented Feb. 27, 1934 BEETHOD OF MAKING SEWING MACHINE NEEDLES Edmund K. Brown, Torrington, Conn, assignor to The Torringtcn (Jompany, Torrington,

Conn, a corporation of Connecticut 4 Claims.

This invention relates to improvements in the art of sewing machine needles, and more particularly to a construction of the same whereby greater strength is assured in the blade of the needle with a corresponding increase in the strength of the structure adjacent the needle eye, along with a lesser liability of breaking the needle thread during the operation of the needle.

it has heretofore been the practice to form a needle with a body wire of round cross-section by, for example, milling a long thread groove in its length and a short thread groove at the eye. These thread grooves must be of sufiicient width and depth to bury the thread during sewing, so

' that the bight or" the thread at the eye is not exposed to direct contact with the fabric when the needle passes through the fabric, and so that the portion of the thread extending from the eye toward the sewing machine spool is contained within this longer thread groove during the entire course of movement of the needle into the fabric. In order to have the thread grooves of sufficient depth, with such a circular cross-section, the web left in the body between the grooves was of restricted thickness, and hence it presented at the eye an insuficient surface to the thread, and the thread was often broken at the relatively sharp edge in the eye, by the effect of a thread tension which was desirable for a proper drawing of the thread loops during sewing.

Furthermore, with such a needle, the grooving of the metal to provide space for burying the thread results in a serious reduction of the radius of gyration of the needle, considered as a loaded column, so that the needle has a much lesser resistance against bending in the plane of symmetry through the thread grooves. Hence greater bending occurred, and breakage of the needle is a frequent result. It is especially to be noted that this grooving not only removes much of the metal in this plane, but also the metal remaining at the sides of the long thread groove is very thin and hence has little ability to resist the bending.

These difficulties are intensified when two long thread grooves are employed.

When it is sought to avoid these defects by employing a body wire of sufiiciently large size to provide an ample web thickness and radius of gyration, the cross-sectional area and perimeter become so great that the fabric is damaged, and the increased displacement of the fabric causes a greater resistance to penetration and a greater wear. The thinness of metal at the sides of the grooves is overcome but slowly with increase of diameter of the body wire, with such a circular cross-section. If the grooves are made shallower, the thread is no longer buried therein, and skipping of stitches and breakages of thread occur from contact of thread and fabric.

When it is sought, by forging or som other process, to deform the body wire at the location of the eye by extending the periphery thereat outside of the general circular periphery of the body Wire itself, the increased cross-sectional area and perimeter requires a larger hole in the fabric for the passage of the portion of the needle adjacent the eye, and the fabric is thereupon momentarily permitted to return by its elasticity when this enlarged portion has passed the fabric and only the normal diameter of the body wire is presented to the fabric. The blade portion of such a needle, however, is no stronger than a needle made in the accepted manner as described above, and bending and breakage occurs. Further, such conformation of the needle may only be produced by a forging or striking operation. The delicate dies required for the needles, especially in the finer sizes, are apt to break, and soon wear. The forging operation, in the plane of the eye, causes the formation of a flash or fin at each side, which must be removed by a further and separate trimming operation. Such needles are, therefore, likewise not wholly satisfactory in service, and are expensive to manufacture.

According to the present invention, the needle is provided with a greater thickness of web between the thread grooves at the eye, and a greater radius of gyration is provided both at the eye as compared to the accepted needle, and along the blade portion between the eye and the shank as compared with any prior needles. These results are attained by a simple and direct method of manufacture which does not require extensive forming dies nor trimming operations.

According to the present method a body wire is formed with an oblong cross-section having a greater diameter along a major axis than along a minor axis, prior to the cutting of the grooves, and then these grooves are out along the major axis plane to an ample depth for fully burying the thread and yet a sufiicient web thickness is left between them for avoiding an edge at the eye so sharp as to cause a cutting or breaking of the thread, and then an eye is formed between the grooves through this web, without substantially changing the form or dimensions of the body along the minor axis.

The needle according to this invention therefore may have the most desirable cross-section from the taper of the point back toward the shank for the entire distance by which the needle may enter or pass through the fabric. My copending and parent application Serial No. 651,435, filed January 12, 1933 discloses and claims this needle.

One form of construction of the needle, in which illustratively the needle has a substantially uniform cross-section at the eye and along the blade, with a procedural representation of steps for the manufacture of the same, is shown on the accompanying drawing, in which:

Fig. 1 is a side elevation of a blank for the needle, as formed in manufacture.

Fig. 2 is a cross-section of this blank at line 2-2 of Fig. 1, being at the point where the needle eye is later to be formed.

Fig. 3 shows the deformation or flattening of the blank of Fig. 1, this section likewise being taken at line 2-2 of Fig. 1.

Fig. 4 shows a further step of manufacture, in which the needle grooves have been formed.

Fig. 5 shows the final stage of forming, in which the eye has been pierced.

Fig. 6 is a longitudinal sectional view, substantially on line 6-6 of Fig. 5.

Figs. '7 and 8 are respectively side elevations in the directions of the arrows '7 and 8 of Fig. 6, showing a preferred shape for the thread grooves.

The present needle is constructed from a blank which has been given an oblong cross-section for the entire length of the body between shank and point, and the thread grooves are formed along the major axis plane of such cross-section. A presently preferred manner of manufacturing a needle according to this invention comprises the formation of a blank having a circular cross-section, in the usual way. Such a blank is shown in Fig. 1 as having a shank 10 by. which it may be held in the needle bar clamp, and a tapering portion 11 joining this shank proper to the body Wire 12.

This blank may be formed by swaging to produce a body wire of circular cross-section as shown in Fig. 2. While the normal gauge of body wire for forming a needle is the same size as the finished needle, according to the present invention, this body wire is preferably ten percent greater in diameter than the standard diameter selected for the finished needle.

In this preferred form of manufacture, the body wire is now flattened for its entire length by the operation of smooth surfaced dies, until the distance between the diametrically opposite flattened sides is reduced substantially to the desired diameter of the finished needle. The body thus assumes an oblong cross-section as shown in Fig. 3, in which the minor axis is the desired finished diameter, while the major axis diameter is considerably greater. This deforming between smooth dies, furthermore, gives a better surface than can be obtained by milling and/or grinding, with lesser frictional effects and wear.

The thread grooves may then be formed in this flattened blank, preferably by milling as this furnishes a groove of definitely determined shape and dimensions. The illustrated long groove 15 is formed for the length of the body wire and extends up onto the tapered portion 11, this long thread groove having its side walls as nearly parallel as feasible with a milling cutter, in this preferred form. Diametrically opposite this long thread groove at the location for the eye is formed, in the illustrative example, a short thread groove 16 which is illustrated with slight tapered walls to permit the thread a relative angular movement about the longitudinal axis of the needle during cooperation with the looper mechanism.

The web 1'7 which forms the bottoms of the two thread grooves is thus of ample thickness between the grooves.

An eye is now formed in this web, with the usual rounded edges, without substantial deformation of the oblong external cross-section at the eye. The usual polishing operation now rounds ofi the edges of the grooves, during which no substantial change of dimensions occurs, owing to the large angle between the peripheral surface and the side walls of the grooves.

The substantially parallel walls of the long thread groove meet the peripheral surface of the body wire at edges which (Figs. 7 and 8) are substantially straight from end to end in the specific form illustrated, and thus afford a groove within which the portion of the thread extending from the eye toward the machine spool may be buried with the least possible removal of material at this critical point.

The width of the groove is standard for the needle size, and the material removed from the body at the major axis plane of the cross-section of the blank, with such proportions and manufacture of the needle, reduces it to substantially the same chordal dimension as the aforesaid minor axis diameter of the blank, and thus to the desired finished diameter of such a needle; (that is, the diameter between the flattened diametrically opposite surfaces is substantially the same as the distance from one longitudinal edge 18 of one thread groove to the symmetrical edge 19 of the other thread groove, measured along a chord of the cross-section).

This preferred manner of forming the body of oblong section is described as flattening in accordance with the usual technical terminology, but it must be understood that this flattening" is not limited to the formation of diametrically opposite plane portions but comprises generally the formation of oblong sections having different diameters along major and minor axes. result of this flattening is to displace metal so that the diameter along any diagonal (i. e. in any plane-other than the major and minor axis planes) is greater than the minor axis diameter. Therefore, when metal has been removed to form a groove, and thus the chordal dimension reduced as aforesaid to the minor axis diameter, the diameters along such diagonals (a and b, Figs. 3 and 5) remain greater than the minor axis diameter, and also greater than the aforesaid chordal dimension. Thus a considerable quantity of metal remains in the structure to provide the side walls of the grooves, and as this metal is at a maximum distance from the center axis of the needle, the effective radius of gyration is increased and a much stiffer needle results. Hence, the finished needle is more resistant to bending, and hence less liable to breakage.

The method thus lends itself to a simple and accurate production of such needles without the employment of expensively manufactured and delicate punching tools for forming the grooves adjacent the eye without the forming of any flash which must be removed, and without the sacrifice of material from the body at this weakest point of the sewing machine needle. The needle produced is characterized by the oblong cross-section between point and shank taper, and by the thickness of web and large radius of curvature permitted at the eye.

The

It is obvious that the invention is not limited to the formation of construction and manufacture shown and described, but that it may be employed in many ways within the scope of the appended claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:-

1. The method of making a sewing machine needle which includes the successive steps of forming a needle body wire having an oblong cross section, thereafter forming diametrically opposite thread grooves in said body wire along the major axis plane thereof while maintaining the cross-sectional shape of the body wire substantially unchanged, and then forming an eye in the web constituting the bottoms of said grooves.

2. The method of making a sewing machine needle which consists in deforming a body wire of circular cross-section larger than the finished diameter to be given the needle to an oblong cross-section in which the minor diameter corresponds to the said finished diameter, forming thread grooves in said body wire along the major axis plane of said cross-section with at least one of said grooves having substantially parallel side wall surfaces and so that the chordal distances between an edge of one said groove and the symmetrical edge of the other said groove is substantially equal to the said finished diameter, and forming an eye in the web constituting the bottoms of said grooves.

3. The method of making a sewing machine needle which includes deforming a body wire of circular cross-section larger than the desired finished diameter to form an oblong cross-section whose minor axis is of the desired finished diameter, and removing material at the ends of the major axis of the cross-section until the needle has chordal external dimensions at the eye substantially equal to the desired finished diameter while forming diametrically opposite thread grooves along the major axis plane.

4. The method of making a sewing machine needle which includes deforming a body wire of uniform circular cross-section larger than the desired finished diameter to form for the entire length thereof an oblong cross-section whose minor axis is of the desired finished diameter, and cutting diametrically opposite thread grooves along the major axis plane of the cross-section, at least one of said grooves having a substantially uniform width through its length at the needle periphery.

EDMUND K. BROWN.

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