Process For Producing Needles For Sewing Machines

Abstract

A process for producing needles for sewing machines by forming a needle blank having a portion of reduced diameter, side rolling the needle blank into an oblong cross section, and press forming said needle blank between a pair of die blocks equipped with a groove-forming projection, said die blocks being brought together along a path substantially aligned with the major axis of said oblong cross section, the groove-forming projection also being substantially aligned with said major axis. A flattened reference plane may be formed in said needle blank to provide a reference for the remaining processes.

Description

STATE OF THE ART

In the process for producing needles for sewing machines, it has been generally well-known that the best mode to provide a groove on the needle blank is to form the groove by die blocks, instead of a number of cumbersome operations required in connection with the utilization of a cutter manufacturing procedure for needles.

In the present procedures, forming of a groove by the press is difficult if the cross section of the needle blank is round. Therefore, attempts have been made to flatten that part of the blank where a groove is to be provided and then to form the groove in the flattened part by the press and thereafter finishing the product into a needle in full roundness by heat treatment. However, this prior press-forming process, known up to the present time as the optimum mode for producing needles, has a distinct disadvantage in that, in the stage wherein a pair of upper and lower die blocks each having a semicircular cavity deform the cross section of the needle blank, a part of needle blank is squeezed out of the gap between the said die blocks before they are closed, whereby burs are produced on the outer surface of the stem portion of needle blank with the result that the die blocks are prevented from coming into contact with each other. Thus, the die blocks heretofore produced were required to take into account the burs, which of necessity must be ground or cut off. As a result, the prior press-forming process has entailed considerable difficulties practically equivalent to well-known difficulties utilizing the process with the cutter. Particularly, in the press process if a part of the needle blank is flattened to facilitate the forming of the groove, the production of burs becomes more evident. Furthermore, the rise on both sides of the groove falls short, and the portion of needle blank which comes in contact with the surface of the dies becomes uneven, thereby making it difficult to attain true roundness of the needle thereby lowering the quality of the product. In addition, the blank tends to develop distortion during heat treatment, and this tendency causes difficulties in the finishing treatment for the final product. Moreover, the prior processes require an increased number of operations and days to produce finished products, resulting in an inefficient production system and labor cost increase.

SUMMARY OF THE INVENTION

The present invention is designed not only to easily eliminate these disadvantages in the prior process but also to make possible a reduction in the number of work process steps. Moreover the present invention intends to bring about a sharp increase in productivity and efficiency in the manufacture of needles as compared with the prior process which requires days to complete furnished products and is inefficient.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a process for producing needles for the sewing machine from a wire rod with the use of die blocks under pressure.

The main object of the invention is also to produce needle rods of full roundness and uniformity by making use of a transformation which the needle blank undergoes at the time of pressing.

A further object of the present invention is to provide a simple but convenient means for simplifying the manufacture of the dies required for the pressing operation and thereby reduce the cost of treatment, thus curtailing the overall production cost and making the unit cost economically low, particularly as to needles applied for industrial utilization.

According to the present invention, the technical objects as mentioned above may be accomplished by a novel and improved needle-manufacturing process in which a needle blank is firstly elongated to form a diametrically reduced portion and then press formed by the use of a pair of die blocks, each having a semicircular forming cavity, to thereby produce a grooved needle for a sewing machine, characterized by the steps of extending a needle stem into a certain selected value of a cross-sectional area taking into consideration deformation of a needle blank during later processing, elongating the extended needle stem in the direction of the movement of the pressing of dies to make a needle blank having an oblong cross section; positioning the oblong cross section of the needle blank in the die blocks in such a manner that the major axis of said oblong cross section is aligned with and in the pressing direction of the die blocks, said die blocks being each provided with a projection for forming a groove on the needle blank, and forming a needle body provided with a groove by pressing the said needle blank between the die blocks.

According to another feature of the present invention, there is provided a novel and improved process for manufacturing needles for sewing machines, comprising the steps of rolling a continuously fed wire rod into a diametrically reduced needle blank having a predetermined cross-sectional area, squeezing the needle blank into one having an oblong cross section placing the needle blank between die blocks with the longer diameter of the needle blank being aligned with the pressing direction, closing said die blocks to each other to thereby form a series of grooves on the needle blank; said grooves being arranged in series either in the same direction or different direction of the travel of the needle blank which is continuously fed into the die blocks, piercing an eye in said groove when the needle blank is withdrawn from the die blocks, and finally cutting the continuous needle blank into separate individual needles defining the final product.

By the use of this process at the same time, the invention will save trouble in processing, provide simplification of processing operations and bring about a marked increase in production efficiency, since the invention permits the easy manufacture of sewing machine needles in mass production, having the properties of full roundness by ingeniously utilizing the deformation of the needle blank at the time of pressing, and production of extremely high quality, uniform products. At the same time the unproductive grinding and polishing steps of the prior-known procedures are eliminated. Since sewing machine needles can be produced by taking advantage of a transformation of needle blank, without the use of cutting tools, the application of this process will result in an economization of manufacturing costs.

The invention also offers automation, consistency and effectuation of each necessary step in the work process by feeding a long steel wire in regular sequential steps. This invention further provides a simple arrangement for the manufacturing steps with the requisite equipment, facilitates simplified adjustments of each step in the respective processing stages and makes possible remote-controlled operation by complete automation.

The attached figures show a preferred embodiment of the present invention.

FIG. 1 shows front and bottom views of a swaged needle blank;

FIG. 2 shows front and side views of a needle having a flattened zone;

FIG. 3 shows front and bottom views of a needle blank after being subjected to pressing operation;

FIG. 4 is an enlarged cross-sectional view taken along the line A-A of FIG. 3;

FIG. 5 shows front and side views of a needle blank after pressing;

FIGS. 6-I, II and III are of enlarged cross-sectional views, respectively, taken along the lines B-B, C-C and D-D of FIG. 5;

FIGS. 7--10 are cross-sectional views of needle blank at various stages of press-forming work as arranged in sequence.

The present invention will be hereinafter described in connection with a preferred embodiment illustrated in the accompanying drawings.

A needle blank of thick steel wire 1 is partially squeezed in a rotary swaging machine to form a diametrically reduced portion 2. A flattened reference plane 3 is then formed on the reduced portion thereof 2 by a press in order to determine a specific radial direction (the plane being perpendicular to the axis of the needle) in cross section of the needle blank. Thereafter, the opposite sides of the stem portion of the needle are pressed or rolled to give the needle blank an oblong cross section.

In this case, it is pointed out that the rolled plane 4 is at a right angle to the reference plane on the needle blank. The needle blank with the oblong cross-sectional portion having thereon outwardly bulged portions 6, and 6 formed by said side pressing is positioned between a pair of die blocks for pressing in such a manner that the bulged portions 6 and 6 will face the pressing direction of the upper die block 10 and the lower die block 11. Thus, a chamfered portion 7, long groove 8 and rear groove 9 are simultaneously formed or stamped in the needle blank by means of the molding surfaces 12, 13, and 14 of the die blocks 10 and 11.

It is important that this forming operation by the die blocks should be applied in the same direction as the reference plane 3 and at a right angle to side-rolled planes 4, and 4. After this press-forming operation the needle blank is pierced to form an eye and then subjected to other necessary processing operations and treatment for a sewing machine needle including polishing and cutting to obtain a finished product.

It is essential to take into consideration the needle blank 1 and the treatments thereof. For example, the diameter should be determined by obtaining the cross-sectional area of a finished product from the cross section at the center of the long groove 8. The cross-sectional area of the needle's eye should be cross-sectional slightly smaller than that of the long groove, and also the metallic distribution should be effectuated so as to allow a part of the blank to bulge outwardly from the stem portion of the needle blank at the time of said press-forming work. It is further essential that at the time of the side press-forming stage, the outwardly bulged portions 6 and 6 of the needle stem 2 be made substantially the same as the stem of the finished needle (in this case, the cross-sectional area after side rolling, being in finished measurement due to this operation, should be made equal to the cross-sectional area of the needle), and that the cross section of the shank section thereof be determined in a similar manner.

It is to be noted that the cross-sectional area dimensions as described above should be determined by taking into account lateral expansion at the time of press forming with the dies, and this can be determined depending on the quality of the metallic material. For example, expansion in the direction of the major axis due to side rolling should be controlled at about 1.5--3.0 percent, or preferably at 2.2 percent, if a favorable rise of needle material (carbon steel containing 0.9--1.1 percent carbon) is to be attained at the time of forming the groove. Accordingly, the longest diameter of the portion of the needle blank having an oblong cross section, as formed by the side rolling should be about 1.5--3.0 percent or preferably 2.2 percent greater than that diameter before such side rolling.

As to the determination concerning the diameter of the wire for rotary swaging, it is advisable that the cross-sectional area at the completion of the rotary swaging process should be slightly larger than the cross-sectional area of the needle blanks after side rolling, since the cross-sectional area tends to decrease due to side rolling as compared with the cross-sectional area at the completion of the rotary swaging processing. For example, the cross-sectional area after swaging should be about 1.0--1.1, or preferably at 1.022 times as large as that of the finished needle blank. The cross-sectional area of the shank should also be increased, but the extent of the increase may be less than that mentioned above.

In the figures, reference numeral 14 represents a projection for the formation of the groove, 15 and 15 represent opposed walls of the groove and 16 represents an eye of the needle.

Since the point of the needle, or the end section extending over the terminal of the long groove, is cut off, a lug (later referred to) may be provided by which the needle blank can be held at the time of press-forming process. Consequently, although side rolling is normally effected along the length of the groove, such pretreatment may be applied therealong.

Further, the needle eye portion 16 of the needle blank is subjected to the abnormally high pressing force and, therefore, it is preferable to form a pair of laterally projected lugs 17 and 17 at the needle eye portion for the purpose of facilitating the working process. These lugs not only contribute to the ease of processing, but offers advantages in that there is no need to deepen grooves, as for example the long groove 8 and rear groove 9, more than required and that the lugs 17 and 17 can also be utilized for determining the position for piercing the needle eye. The lugs 17 and 17 are cut off at the time of piercing of the needle eye, or removed grinding, or other operation, and the surface around the eye is finished to a smooth surface.

In case the needle blanks are continuously produced from a wire material, the continuous production of the needly blank may be made either in the unidirectional or alternately directional manner. Continuous, automatic production of the needle blanks can be made with the use of either round or deformed wire rod. It is convenient to select the cross-sectional area of the stem section of the needle blank for the shank section of the needle blank and use a wire rod with the diameter which reflects the allowance for some expansion. In the case of round wire rod, the forming of both edges of the chamfered section 7 may possibly be incomplete, and therefore it is convenient to form these edges by applying some side rolling, thus extending the side-rolling treatment up to this section 7 in order to meet the specifications of needles.

Claims

What I claim is:

1. A process for producing needles for sewing machines from a continuous wire comprising the steps of progressively advancing said wire; linearly extending a segment of said wire to reduce the cross-sectional area thereof to define a needle stem portion of a needle blank; operating on said stem portion to produce an oblong cross section having a major axis; and press forming said needle blank between a pair of die blocks with the major axis of said oblong cross section substantially aligned with the pressing direction of said blocks, each of said blocks being formed with a projection substantially aligned with said major axis for forming a groove in said needle blank.

2. A process for producing needles as recited in claim 1, wherein the cross-sectional area of said needle stem portion of said needle blank after linear extension is about 1.01--1.1 times as large as the cross-sectional area of the finished sewing machine needle.

3. A process for producing needles as recited in claim 1, wherein the steps of linearly extending a segment of said wire, operating on said needle stem portion, and press-forming said needle blank are successively and repetitively applied to successive lengths of said wire for the production of a plurality of said needles.

4. A process for producing needles for sewing machines from a continuous wire comprising the steps of progressively moving said wire, forming a diametrically reduced segment of said wire by applying a rotary swaging device to define, in part, a needle blank; forming a flattened reference plane on said reduced segment; side rolling at least a portion of said needle blank to redistribute the metal of said needle blank into an oblong cross section having a major axis oriented in a predetermined relation to said reference plane; and press forming said needle blank between a pair of die blocks equipped with a groove-forming projection, said needle blank being positioned during said press forming with the major axis thereof substantially aligned with said groove-forming projection and the direction of pressing.

5. A process for producing needles as recited in claim 4, wherein said press-forming direction is substantially aligned with said reference plane and substantially perpendicular to the plane defined in said needle blank by said side rolling.

6. A process for producing needles as recited in claim 4, wherein the diameter of said needle blank defined by said major axis of said oblong cross section produced by such side rolling is about 1.5--3.0 percent greater than the diameter of that region of said needle blank before said side-rolling step.

7. A process for producing needles as recited in claim 4, wherein the cross-sectional area of said needle stem portion of said needle blank after said rotary swaging step is about 1.01--1.1 times as large as the cross-sectional area of the finished sewing machine needle.

8. A process for producing needles for sewing machines as recited in claim 4, wherein said die blocks are provided with a die cavity, said side-rolling step being adapted so that the diameter defined by the major axis of said oblong cross-sectioned portion of said needle blank is greater than the diameter of said portion of said needle blank before said side-rolling step by an amount such that, during the press-forming step, the metal of said needle blank will be laterally redistributed relative to said major axis by said groove-forming projection to substantially occupy but not extend beyond said die cavity.