System and method for manufacturing reduced thread height point fasteners

Abstract

A system and method for manufacturing reduced thread height point fasteners. Thread rolling dies are created with a first set of grooves designed to form the body threads on a blank fastener and a second set of grooves, which may vary over the length of the die, to form the lead threads on the blank fastener. The second set of grooves are designed to minimize the flat surface areas on the shaft of the fastener between the lead threads, thereby reducing the known manufacturing problems in producing variable height thread fasteners using thread rolling.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 63 / 772,974, which was filed on Mar. 17, 2025, by John R. Reynolds for SYSTEM AND METHOD FOR MANUFACTURING REDUCED THREAD HEIGHT POINT FASTENERS, which is hereby incorporated by reference.BACKGROUND

[0002] Thread rolling is a well-known technique for the creation of threaded fasteners, such as screws or bolts. A blank fastener is compressed between two dies, which form the blank to create the desired threads thereon. A noted disadvantage occurs when fasteners have lead threads of a reduced height compared to the body threads. In such cases, the face of the roll thread die has a flat area between the threads that make it difficult to move material into the thread forms. Further, the extreme manufacturing rolling pressure on the point area may cause the blank point to flex and bend. Depending on the fastener's threaded body length, the blank may skip and / or not feed true. This may cause the blank to be off the desired perpendicular orientation to the roll thread die.

[0003] One prior art technique is described in U.S. Pat. No. 4,255,959, entitled DIES FOR MAKING THREAD-FORMING SCREW WITH STEP TAPER, issued Mar. 17, 1981. This technique is designed for use with thread-forming screws that have steep entry angles for the point, e.g., a gimlet point thread-forming screw.

[0004] However, the technique described above does not solve the noted problems with threaded fasteners that have reduced heights of lead threads, but not steep entry angles. An example of such a fastener is described in U.S. Pat. No. 9,835,193 entitled FASTENER SYSTEM COMPRISING AN EXTERNALLY THREADED BOLT AND AN INTERNALLY THREADED NUT FOR THE AVOIDANCE O CROSS-THREADING OF THE MATING THREADS DURING ASSEMBLY, the contents of which are hereby incorporated by reference. It is thus desirous for a technique to produce threaded fasteners with variable height threads.SUMMARY

[0005] The present invention is directed to systems and method for manufacturing reduced thread height point fasteners. Illustratively, thread rolling dies are created with a first set of grooves designed to form the body threads on a blank fastener and a second set of grooves, which may vary over the length of the die, to form the lead threads on the blank fastener. The second set of grooves are designed to minimize the flat surface areas on the shaft of the fastener between the lead threads, thereby reducing the known problems of slipping, bending, etc.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The above and further advantages of the present invention are described below in conjunction with the accompanying figures in which like reference numbers indicate identical or functional similar elements, of which:

[0007] FIG. 1 is a side view of an exemplary threaded fastener in accordance with an illustrative embodiment of the present invention;

[0008] FIG. 2 is a perspective view of exemplary flat roll thread dies in accordance with an illustrative embodiment of the present invention;

[0009] FIG. 3 is a view of exemplary cylindrical roll thread dies in accordance with an illustrative embodiment of the present invention;

[0010] FIG. 4 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0011] FIG. 5 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0012] FIG. 6 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0013] FIG. 7 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0014] FIG. 8 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0015] FIG. 9 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0016] FIG. 10 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0017] FIG. 11 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention;

[0018] FIG. 12A is a side view of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention;

[0019] FIG. 12B is a side view of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention;

[0020] FIG. 12C is a side view of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention;

[0021] FIG. 12D is a side view of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention; and

[0022] FIG. 12E is a side view of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention.DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

[0023] FIG. 1 is a side view of an exemplary threaded fastener 100 in accordance with an illustrative embodiment of the present invention. Exemplary threaded fastener 100 comprises a shaft 105 and a head 110. Head 110 is utilized by a screwdriver or other tool to provide necessary torque to insert the fastener into a nut member (not shown). The shaft 105 illustratively comprises two differing thread profiles, namely, a body thread profile 115 and an entry (or lead) thread profile 120. Illustrative fastener 100 is that described in the above-incorporated U.S. Pat. No. 9,835,193. However, it is expressly contemplated that alternative thread profiles, maybe utilized in alternative embodiments of the present invention. Further, while exemplary threaded fastener 100 is shown as having two different thread profiles, it is expressly contemplated that alternative numbers of thread profiles maybe utilized in accordance with alternative embodiments of the present invention. Therefore, the description and depiction of a threaded fastener 100 having only body threads 115 and lead threads 120 should be taken as exemplary only.

[0024] As can be seen in FIG. 1, the lead thread profile region 120 includes substantial flat areas 125 located between the spaced apart threads. It is these flat areas 125 that can cause adverse results during a thread rolling process when using a conventional roll threading die. As noted above, the rolling pressure on these blank areas may cause the shaft to flex and / or bend. Additionally, the blank may skid or not feed true, therefore resulting in a manufactured fastener 100 that does not have the desired thread profiles.

[0025] Embodiments of the present invention are directed to systems and methods for manufacturing fasteners that have such substantial flat areas 125 in a manner that reduces and / or eliminates these manufacturing irregularities.

[0026] FIG. 2 is a perspective view 200 of exemplary flat roll thread dies in accordance with an illustrative embodiment of the present invention. As will be appreciated by those skilled in the art, view 200 illustrates a stylistic representation of the thread rolling process. A stationary die 210 and a movable die 215 each include a series of grooves and valleys 215, 220. These are arranged so that when a fastener 100 is placed between them and the movable die 205 rolls the fastener 100 along the grooves 215, 220 suitable threads 105 are formed. It should be noted that in view 200 a stylistic set of threads 105 are shown and not the multiple thread profiles as described above in relation to FIG. 1.

[0027] In accordance with illustrative embodiments of the invention, these grooves / valleys 215, 220 are formed in such a manner to reduce or eliminate the large flat areas 125 on the fastener during the manufacturing process. Various alternative embodiments are shown and described in relation to FIGS. 5-9, described further below.

[0028] FIG. 3 is a view 300 of exemplary cylindrical roll thread dies in accordance with an illustrative embodiment of the present invention. View 300 illustrates an alternative technique for thread for row threading that utilizes cylindrical thread dies 310, 315, each having suitable thread forming grooves / valleys 215, 220 engraved on their face. Mount 305 supports the metal threaded faster 100 that is pressed between the two cylindrical roll thread dies 310, 315. Exemplary view 300 is shown to illustrate that there are alternative techniques to the linear or flat thread dies described above in relation to FIG. 2. While the remainder of this description is written and shown in reference to flat dies, it is expressly contemplated that the principles of the present invention may be utilized in other thread rolling environments. Therefore, the description of flat dies should be taken as exemplary only.

[0029] FIG. 4 is a side view 400 of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 400 illustratively shows the movable die 205 interfacing with the fastener 100. However, it should be noted that the same principles apply to the stationary die 210. Therefore, the description and illustration of movable die 205 should be taken as exemplary only. Exemplary view 400 illustrates a conventional die that may be utilized in accordance with present manufacturing processes. The die face includes a plurality of grooves / valleys 215 that during operation create threads 115, 120.

[0030] However, as noted above, the conventional dies result in substantial flat areas 125 between lead threads 120. These flat areas 125 may cause imperfections during the manufacturing process. Therefore, it is a desired goal of various embodiments of the present invention to create dies that are designed to reduce or eliminate these flat areas 125 to therefore avoid the noted disadvantages of conventional manufacturing processes.

[0031] FIG. 5 is a side view 500 of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 500 is of an exemplary first embodiment in which the thread depths 505 of the die for the lead threads 120 are initially increased to match the body threads 115. Over the course of the length of the die, the grooves 505 used to form the threads the lead threads 120 are gradually reduced as shown by the reduced lines 505. In this way, the flat areas 125 are smaller than that shown above in relation to FIG. 4 during the initial formation, which avoids the noted disadvantages of extremely large flat areas 125 on the shaft of the threaded fastener.

[0032] FIG. 6 is a side view 600 of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 600 is of an exemplary second embodiment, but utilizes a similar concept as the embodiment described above in relation to FIG. 5; however, the grooves for the die for the lead threads 120 have an increased root ratio 605 that forms a substantially parabolic shape. This large root ratio reduces the flat areas 125 on the face of the die 125. Similar to that described above in relation to FIG. 5, as the die progresses along the depth of the grooves decreases over the length to thereby create the desired lead threads 120.

[0033] FIG. 7 is a side view 700 of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 700 illustrates a third exemplary embodiment in which an initial thread form is then followed by a separate cutter to modify the existing form. Alternatively, a dual angle cutter may be used only for the point threads. Again, this significantly reduces the flat areas under the shaft of the faster during initial during the initial phases of manufacturing common. This prevents the noted disadvantages from occurring. As the fastener is more fully engaged in the role, thread dies, the shape of the grooves 705 progressively decrease to create the flat areas 125. However, as these flat areas are not present during the initial stages of manufacturing, the slippage, etc. that may occur using conventional techniques is avoided.

[0034] It should be noted that in view 700, the initial groove profile 705 for the last lead thread before the body threads has an asymmetrical shape compared to the grooves 705 for the other lead threads. While this provides some noted advantages, it is not necessary. Therefore, the description and depiction of an asymmetric groove profile should be taken as exemplary only.

[0035] FIG. 8 is a side view 800 of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 800 illustrates a fourth exemplary embodiment in which the point thread grooves 805 are initially deeper than the body threads. This extra depth in the grooves 805 reduces the flat areas 125 to an acceptable level. As the die progresses, the grooves 805 gradually reduce in size until the desire lead threads 120 are formed. Illustratively, there is a different sized groove 810 for the last lead thread before the body threads.

[0036] FIG. 9 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 900 illustrates a fifth exemplary embodiment in which the groove 905 for the first lead thread adjacent to the body threads 115 is shifted towards the tip of the fastener. This serves to reduce the flat area 125 between the first and the second lead threads. The grooves 910 for the remaining lead threads 120 are aligned with the threads that they are forming.

[0037] FIG. 10 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 1000 illustrates an exemplary embodiment for a thread rolling fastener, such as the exemplary TAPTITE II ® fastener available from Research Engineering & Manufacturing, Inc, of Middletown, Rhode Island. In embodiment 1000, a plurality of grooves 1005 vary over the length of the die from a heigh equal to the body threads 115 down to the desired predefined height of the lead threads 120. In this way, the flat areas 125 are minimized during the manufacturing process.

[0038] FIG. 11 is a side view of an exemplary die face interfacing with a fastener in accordance with an illustrative embodiment of the present invention. View 1100 illustrates a completed thread rolling fastener after all grooves 1005 have been engaged by the fastener blank.

[0039] FIG. 12A is a side view 1200A of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention. In view 1200A, the cutting edge 1205 of the die is substantially larger than the end thread. As the die progresses (FIGS. 12A-12E), the cutting edge decreases in size until the final thread shape is formed. However, due to the large cutting edge 1205, the flat area 125 between threads is reduced, thereby avoiding the noted disadvantages of large flat areas.

[0040] FIG. 12B is a side view 1200B of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention. View 1200B is further along the die than view 1200A. In this view, the cutting edge 1210 is further reduced from edge 1205.

[0041] FIG. 12C is a side view 1200C of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention. Again, cutting edge 1215 is further reduced to create a smaller thread. However, by this point in the die, the flat area 125 has increased. However, as the blank is now firmly engaged with the dies, the possibility of slippage, etc. is reduced / eliminated.

[0042] FIG. 12D is a side view 1200D of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention. The cutting edge 1220 of the die is now even further reduced. Material 1225 from the blank is being formed into the thread shape.

[0043] FIG. 12E is a side view 1200E of an exemplary progression of a thread being formed in accordance with an illustrative embodiment of the present invention. In view 1200E, the thread 120 has been formed in its final shape and the flat space 125 between threads is now fully formed. As noted, as the blank is fully engaged with the dies, the risk of slippage, etc. is minimized / eliminated.

[0044] What has been shown and described are various illustrative embodiments of forming a threaded fastener that has large spacings between individual threads. While the description contained herein has been directed to embodiments where the lead threads (of a multi-thread type fastener) have the large spacings, the principles of the present invention may be utilized in alternative embodiments.

Claims

1. A system for thread rolling a fastener, the system comprising:a first die, the first die having:a first set of grooves, the first set of grooves configured to form a first set of threads on the fastener when the fastener is rolled between the first die and a second die, anda second set of grooves, the second set of grooves configured to form a second set of threads on the fastener when the fastener is rolled between the first die and the second die; andthe second die having:a third set of grooves, the third set of grooves configured to form the first set of threads on the fastener when the fastener is rolled between the first die and the second die, anda fourth set of grooves, the fourth set of grooves configured to form the second set of threads on the fastener when the fastener is rolled between the first die and the second die.

2. The system of claim 1 wherein the first set of grooves are identical to the third set of grooves.

3. The system of claim 1 wherein the second set of grooves are identical to the fourth set of grooves.

4. The system of claim 1 wherein the first set of threads are body threads.

5. The system of claim 1 wherein the second set of threads are lead threads6. The system of claim 1 wherein the second set of threads have a reduced height compared to the first set of threads.

7. The system of claim 1 wherein the second set of grooves begins at a start point of the first die having a same depth as the first set of grooves wherein the depth reduces over a length of the first die to a predefined depth associated with the second set of threads.

8. The system of claim 1 wherein the second set of grooves has an initial substantially parabolic shape at a start point of the first die, wherein the substantially parabolic shape works to minimize flat areas between individual threads of the second set of threads; andwherein the second set of grooves transitions over a length of the first die to a shape to form the second set of threads.

9. The system of claim 1 wherein the second set of grooves has an initial thread form; andwherein the second set of grooves has a separate cutter to modify the initial thread form to form the second set of threads.

10. The system of claim 1 wherein the second set of grooves have a depth greater than a depth of the first set of grooves at a start point of the first die and transition to a lower depth over the course of the first die to result in a final depth equal to a predefined depth of the second set of threads.

11. The system of claim 1 wherein a first groove of the second set of grooves is shifted relative to where a first thread of the second set of threads is located.

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