Shrunken fastener with locally controlled thread height

Abstract

The male anti-cross threaded fastener comprises a generally rounded shank having a leading end, a torque end, and a plurality of male threads around the circumference of the shank, the plurality of male threads being standard threads around at least a portion of the circumference of the shank and having a standard thread profile, the standard thread width and thread angle allowing engagement with a corresponding female thread, the standard thread major diameter being between a lower major diameter limit and an upper major diameter limit; a transition thread having a transition thread profile around at least a portion of the circumference of the shank and with a width and thread angle similar to the standard thread width and thread angle allowing engagement with the corresponding female thread; a anti-cross thread around at least a portion of the circumference of the shank and having a anti-cross thread profile and major diameter configured to facilitate alignment of the male anti-cross thread fastener with the female fastener; and a leading thread.

Description

Technical Field

[0001] (Technical Field) The present disclosure generally relates to the field of threaded fasteners such as screws and bolts, and more specifically to transition threads at the leading end of a thread helix.

Background Art

[0002] (Background) U.S. Patent No. 5,836,731, which is incorporated herein by reference in its entirety, discloses an anti-cross-threading fastener. FIG. 1 shows a side view of a known anti-cross-threading fastener in which the thread helix differs from most fastener threads in that the helix has four sequential profiles over its entire length rather than a standard thread profile. These four thread profiles are (i) a standard ISO type thread profile 10 wound around the shaft of the fastener for most of the helical coil (the number of such coils is determined according to the requirements to achieve the desired functional thread length), (ii) a transition thread profile 20 adjacent to the standard thread profile, (iii) an anti-cross-threading thread profile 30 having a radial profile as described in U.S. Patent No. 5,836,731 and a length of approximately one full turn of the helix, and (iv) a leading thread profile 40 having a length of 1 / 8 turn to several turns of the helix and functioning to bite the thread helix into engagement with a female thread (enumerated in order from the fastener head to the leading end). U.S. Patent No. 9,644,664, which is incorporated herein by reference in its entirety, describes a profile for the leading thread 40 that gives the fastener improved anti-misthreading performance. U.S. Patent No. 6,561,741, which is incorporated herein by reference in its entirety, describes a profile for the leading thread 40 that gives improved biting performance and aligns the fastener. The leading thread profile 40 may also have other quasi-ideal profiles. Anti-cross-threading and anti-misthreading fasteners are generally sold under the trademarks MAThread® and MATpoint®.

[0003] The transition thread profile 20 has two main functions, namely, (i) to form a smoothly blended transition between the standard ISO type thread profile 10 and the anti-crossing thread profile 30, and (ii) not to interfere with or overly contact the female thread during screwing. Both of these functions are non-structural and do not require a standard thread of full height.

[0004] To implement the first function, the transition thread profile 20 has one end that smoothly blends with the standard ISO type thread profile 10 and the other end that smoothly blends with the radial outer profile of the anti-crossing thread profile 30. The height of the anti-crossing thread profile 30 is approximately half of the height of the standard ISO type thread profile 10. The transition thread profile 20 must provide a smooth transition between these thread heights.

[0005] To implement the second function, the transition thread profile 20 decreases in height over its length. FIG. 2 shows a cross-sectional view of two adjacent threads of the fastener obtained along the longitudinal central axis of the fastener shaft portion 14. The threads have standard parts. For example, the standard ISO type thread profile 10 has a valley portion 11, an inclined surface 12, and a top portion 13, and the thread angle of the inclined surface 12 is approximately 60 degrees. The inclined surface 12 is flat and extends from the valley portion 11 to the top portion 13. The standard ISO type thread profile 10 is the highest thread having a standard thread major diameter 16. The anti-crossing thread profile 30 has an anti-crossing thread outer diameter 36 such that there is a difference in height 62 and the height is approximately half. The transition thread profile 20 should transition without interfering with the female thread of the female fastener as they engage with the leading thread profile 40 and the anti-crossing thread profile 30.

[0006] Figures 3A - 3H provide a series of sequential cross - sectional views obtained through the transitional thread profile 20 as it wraps around the fastener shaft portion 14. The straight line 61 extends across the upper part of the transitional thread profile 20 in these figures, illustrating a constant reduction in height as the thread helix wraps around the shaft portion 14. The transitional thread profile 20 is a hybrid or fusion of the ISO - type standard thread profile 10 (see Figure 3A) and the anti - interference thread profile 30 (see Figure 3H). As the standard portion 21 of the transitional thread profile 20 decreases in height, an increasing amount of the anti - interference portion 22 protrudes, forming the inclined surface 12 into the valley 11. The transitional thread profile 20 first appears as a slightly shorter standard thread profile (see Figure 3B), the inclined surface 12 is at the same angle, and the width of the top 13 is the same as that of the standard ISO - type standard thread profile 11. The difference in the profile is shifted downward, and thus the thread becomes shorter and the width between the valleys 11 becomes narrower. In Figure 3D, the standard portion 21 of the thread is further shifted downward, and thus the transitional thread profile 20 becomes even shorter. Also, with the standard portion 21 shifted downward, the anti - interference portion 22 bulges from the inclined surface adjacent to the valley 11. In Figure 3E, the standard portion 21 is further shifted downward, and thus the transitional thread profile 20 becomes even shorter, and the anti - interference portion 22 forms an even greater amount of the inclined surface 12 adjacent to the valley 11. In Figure 3F, the anti - interference portion 22 becomes dominant, and the standard portion 21 forms a tip at the upper part of the transitional thread profile 20. In Figure 3F, the transitional thread profile 20 is similar to that shown in Figure 3G, but the tip of the standard portion 21 protruding at the upper part of the anti - interference portion 22 is even shorter and narrower. Importantly, as shown in Figures 3B - 3G, the top 13 at the upper part of the standard portion 21 maintains the same width, and the inclined surface 12 of the standard portion 21 maintains the same inclined surface angle.

[0007] Figures 4A - 4H provide a series of sequential cross - sectional views obtained through another known transition thread profile 20 as it wraps around the fastener shaft portion 14. Instead of shifting the standard portion 21 downward, this transition thread profile 20 widens the slope angle of the slope 12 of the standard portion 21. The transition thread profile 20 first appears as a slightly shorter standard thread profile (see Figure 4B), where the width of the top 13 is the same as that of the standard ISO - type standard thread profile 11, but the slope 12 is angled slightly wider so as to extend to the valley 11. In Figures 4C - 4E, the transition thread profile 20 is shortened by maintaining the width of the top 13, angling the slope 12 wider, and extending it to the valley 11. In Figure 4F, the height of the transition thread profile 20 continues to be shortened such that the anti - interference portion 22 bulges, forms a slope into the valley 11, the slope 12 of the standard portion 21 is widened, and blends into the profile of the anti - interference portion 22. In Figure 4G, the anti - interference portion 22 predominates, with only a small bulge having the top 13 at the upper part, and a very wide slope 12 blends into the profile of the anti - interference portion 22.

[0008] The known transition thread profile 20 that performs this transition varies between the overlapping profiles shown in Figures 3B - 3G and the more smoothly blended profiles shown in Figures 4B - 4G. Any shape between these profiles is suitable for performing the transition function.

[0009] The second function of the transition thread profile, i.e., not interfering with the female thread during use, can be satisfied at a thread height such that it does not interfere with and / or does not become so high as to block the internal female thread of the female fastener during the cam action of the male anti-crossing thread fastener at any location along its length. The height reduction in the essentially linear rate as the helix progresses around from the full thread height to the anti-crossing thread has been satisfactory. For example, the metric transition thread of M8×1.25 6g is used in combination with a constant height reduction rate of about 0.0015 mm per turn of the helix. In FIGS. 3A-3H and 4A-4H, the straight line 61 extends across the upper part of the transition thread profile 20, illustrating a constant reduction in height as the thread helix winds around the shaft portion 14. The transition thread profile 20 having lengths of 1 / 4 turn (90 degrees) to 1 turn and 1 / 4 turn (450 degrees) is utilized.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Means for Solving the Problems

[0011] (Abstract) Therefore, there is a need for an improved anti-crossing thread fastener.

[0012] According to an aspect of the present invention, there is provided a male cross-preventing screw fastener having a substantially rounded shaft portion, the shaft portion having a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, the plurality of male threads being at least around a portion of the circumference of the shaft portion and being standard threads having a standard thread profile, the width and thread angle of the standard threads enabling engagement with corresponding female threads, the major diameter of the standard threads being between a lower major diameter limit and an upper major diameter limit, standard threads; transition threads having a width and thread angle similar to those of the standard threads and having a transition thread profile at least around a portion of the circumference of the shaft portion and enabling engagement with corresponding female threads; anti-crossing threads having an anti-crossing thread profile and an outer diameter at least around a portion of the circumference of the shaft portion and configured to facilitate alignment of the male cross-preventing screw fastener and the female fastener; and leading threads having a leading thread profile at least around a portion of the circumference of the shaft portion, the transition thread profile transitioning in height from the lower major diameter limit of the standard threads to the outer diameter of the anti-crossing threads, a male cross-preventing screw fastener is provided.

[0013] Another aspect of the present invention is a male anti-cross-threading screw fastener having a generally rounded shaft portion, the shaft portion having a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, the plurality of male threads being around at least a portion of the circumference of the shaft portion and having a standard thread profile defined by a valley portion, a flat top portion, and a flat slope from the valley portion to the top portion, and a thread angle of about 60 degrees, the major diameter of the standard thread being between a lower major diameter limit and an upper major diameter limit; a transition thread having a transition thread profile defined by a valley portion, a flat top portion, and a flat slope from the valley portion to the top portion, and a thread angle of about 60 degrees, the transition thread being around at least a portion of the circumference of the shaft portion and forming a continuous helix with the standard thread; an anti-cross-threading thread having an anti-cross-threading thread profile and an outer diameter configured to facilitate mating with a female fastener of the male anti-cross-threading screw fastener, the anti-cross-threading thread being around at least a portion of the circumference of the shaft portion and forming a continuous helix with the transition thread; and a leading thread having a leading thread profile, the leading thread being around at least a portion of the circumference of the shaft portion and forming a continuous helix with the anti-cross-threading thread, wherein as the transition thread profile transitions from the standard thread profile to the anti-cross-threading thread profile, the top of the transition thread profile widens and the height of the transition thread profile shortens, thereby providing a male anti-cross-threading screw fastener.

[0014] According to yet another aspect of the present invention, there is provided a male cross-preventing screw fastening device, comprising a substantially rounded shaft portion having a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, the plurality of male threads being around at least a part of the circumference of the shaft portion and having a standard thread profile defined by a valley portion at a minimum diameter, a flat top portion at a major diameter, and a flat slope from the valley portion to the top portion, the standard thread having a width at a certain pitch diameter and a thread angle of about 60 degrees, the major diameter of the standard thread being between a lower major diameter limit and an upper major diameter limit, a transition thread profile around at least a part of the circumference of the shaft portion, defined by a valley portion, a flat top portion, and a flat slope from the valley portion to the top portion, a transition thread that forms a continuous helix with the standard thread, having a thread angle of about 60 degrees and a height below the lower major diameter limit of the standard thread profile, the transition thread winding around the shaft portion for less than about 5 / 8 turn (225 degrees), and a cross-preventing thread that forms a continuous helix with the transition thread, around at least a part of the circumference of the shaft portion and having an outer diameter substantially the same as the pitch diameter of the standard thread, the cross-preventing thread profile having a shape defined by a curve extending from a curve in the valley portion to substantially the outer diameter. The present invention provides, for example, the following items. (Item 1) A male-type cross-preventing screw fastener, comprising a shaft portion having a substantially rounded shape, wherein the shaft portion has a leading end, a torque end, and a plurality of male screw threads around the circumference of the shaft portion, wherein the plurality of male screw threads are standard screw threads that are around at least a part of the circumference of the shaft portion and have a standard thread profile, and the width and thread angle of the standard screw threads enable engagement with a corresponding female screw thread, and the major diameter of the standard screw threads is between a lower major diameter limit and an upper major diameter limit, and are transition screw threads that are around at least a part of the circumference of the shaft portion and have a transition thread profile with a width and thread angle similar to those of the standard screw threads that enable engagement with a corresponding female screw thread, are anti-crossing screw threads that are around at least a part of the circumference of the shaft portion and are configured to facilitate alignment between the male-type cross-preventing screw fastener and a female fastener, and have an anti-crossing thread profile and an outer diameter, are leading screw threads that are around at least a part of the circumference of the shaft portion and have a leading thread profile, and are provided with wherein the transition thread profile has a height that transitions from the lower major diameter limit of the standard screw threads to the outer diameter of the anti-crossing screw threads, a male-type cross-preventing screw fastener. (Item 2) The anti-crossing screw fastener according to Item 1, wherein the standard screw threads are wound around the shaft portion for at least 2 turns (720 degrees). (Item 3) The anti-crossing screw fastener according to Item 1, wherein the transition screw threads are wound around the shaft portion for less than about 5 / 8 turn (225 degrees). (Item 4) The anti-crossing screw fastener according to Item 1, wherein the anti-crossing screw threads are wound around the shaft portion for 1 turn (360 degrees) to 2 turns (720 degrees). (Item 5) The anti-crossing screw fastener according to Item 1, wherein the leading screw threads are wound around the shaft portion for 1 / 2 turn (180 degrees) to 2 turns (720 degrees). (Item 6) The anti-crossing screw fastener according to Item 1, wherein the standard screw threads have a thread angle of about 60 degrees, and the transition screw threads have a thread angle of about 60 degrees from the root to the crest. (Item 7) The anti-crossing screw fastener according to Item 1, wherein the transition thread profile has a top that widens as the height transitions from the lower major diameter limit of the standard screw threads to the outer diameter of the anti-crossing screw threads. (Item 8) The outer diameter of the anti-crossing thread is substantially the same as the pitch diameter of the standard thread, and the anti-crossing thread profile has a shape defined by a curve that extends from the curve at the valley portion to substantially the outer diameter. The anti-crossing screw fastening device according to item 1. (Item 9) The standard thread, the transition thread, the anti-crossing thread, and the leading thread include a continuous thread helix around the shaft portion. The anti-crossing screw fastening device according to item 1. (Item 10) The anti-crossing screw fastening device according to item 1, further comprising a biting point at the leading end of the shaft portion. (Item 11) The biting point has a variable outer diameter and length. The variable outer diameter is maximum near the leading end of the shaft portion and becomes smaller toward the end of the biting point distal from the leading end of the shaft portion. The anti-crossing screw fastening device according to item 10. (Item 12) A male anti-crossing screw fastening device, comprising a shaft portion with a slightly rounded shape, the shaft portion having a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, the plurality of male threads being a standard thread having a standard thread profile defined by a valley portion, a flat top, and a flat slope from the valley portion to the top, and a thread angle of about 60 degrees, and the major diameter of the standard thread being between a lower major diameter limit and an upper major diameter limit, the standard thread being a transition thread having a transition thread profile defined by a valley portion, a flat top, and a flat slope from the valley portion to the top, and a thread angle of about 60 degrees, and forming a continuous helix with the standard thread, the transition thread being around at least a part of the circumference of the shaft portion, an anti-crossing thread having an anti-crossing thread profile and an outer diameter configured to facilitate alignment with a female fastening device of the male anti-crossing screw fastening device, and forming a continuous helix with the transition thread, the anti-crossing thread being around at least a part of the circumference of the shaft portion, a leading thread having a leading thread profile and forming a continuous helix with the anti-crossing thread, the leading thread being around at least a part of the circumference of the shaft portion are provided, As the transition thread profile transitions from the standard thread profile to the anti-crossing thread profile, the top of the transition thread profile becomes wider and the height of the transition thread profile becomes shorter. The anti-crossing screw fastening device. (Item 13) The transition thread is less than about 5 / 8 turn (225 degrees) wound around the shaft portion, the anti-crossing screw fastener according to item 12. (Item 14) The outer diameter of the anti-crossing thread is substantially the same as the pitch diameter of the standard thread, and the anti-crossing thread profile has a shape defined by a curve that extends from the curve in the valley portion to substantially the outer diameter, the anti-crossing screw fastener according to item 12. (Item 15) The standard thread, the transition thread, the anti-crossing thread, and the leading thread have a continuous thread helix around the shaft portion, the anti-crossing screw fastener according to item 12. (Item 16) The anti-crossing screw fastener according to item 12, further comprising a biting point at the leading end of the shaft portion. (Item 17) The biting point has a variable outer diameter and length, and the variable outer diameter is maximum close to the leading end of the shaft portion and becomes smaller towards the end of the biting point distal from the leading end of the shaft portion, the anti-crossing screw fastener according to item 16. (Item 18) A male anti-crossing screw fastener, comprising a shaft portion with a slightly rounded shape, the shaft portion having a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, the plurality of male threads are around at least a part of the circumference of the shaft portion, having a standard thread profile defined by a valley portion at the minimum diameter, a flat top at the maximum diameter, and a flat slope from the valley portion to the top, having a width at a certain pitch diameter and a thread angle of about 60 degrees, the standard thread, wherein the major diameter of the standard thread is between a lower major diameter limit and an upper major diameter limit, the standard thread, and are around at least a part of the circumference of the shaft portion, having a transition thread profile defined by a valley portion, a flat top, and a flat slope from the valley portion to the top, a thread angle of about 60 degrees, and a height below the lower major diameter limit of the standard thread profile, the transition thread forming a continuous helix with the standard thread, the transition thread being less than about 5 / 8 turn (225 degrees) wound around the shaft portion, the transition thread, and are around at least a part of the circumference of the shaft portion, having an anti-crossing thread profile with an outer diameter substantially the same as the pitch diameter of the standard thread, the anti-crossing thread forming a continuous helix with the transition thread and comprising. The anti-crossing thread profile has a shape defined by a curve that extends from the curve in the valley portion to substantially the outer diameter, and is an anti-crossing screw fastening tool. (Item 19) The anti-crossing screw fastening tool according to Item 18, further comprising a leading thread that is located around at least a part of the circumference of the shaft portion and has a leading thread profile, and forms a continuous helix with the anti-crossing thread. (Item 20) The anti-crossing screw fastening tool according to Item 18, further comprising a biting point at the leading end of the shaft portion.

[0015] A more complete understanding of the present disclosure can be obtained by reference to the following description considered in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

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Figure 10

Figure 11

Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0017] The present disclosure may cover various modifications and alternative forms, and specific exemplary embodiments thereof are shown in the drawings and described in detail herein. However, the description of the specific exemplary embodiments herein is not intended to limit the present disclosure to the specific forms disclosed herein. On the contrary, it should be understood that the present disclosure covers all modifications and equivalents as defined by the appended claims.

[0018] (DETAILED DESCRIPTION) According to the teachings of the present disclosure, shorter fasteners are possible while maintaining thread engagement and anti-crossing thread functionality.

[0019] Aspects of the present invention address what was previously the "fixed" length of the transition thread profile of the thread helix on an anti-crossing screw fastener. Aspects of the present invention include a method of reducing the length of the transition thread profile of the thread helix on an anti-crossing screw fastener while maintaining full anti-crossing thread functionality.

[0020] The length of the transition thread profile was previously considered "fixed" because the height transition could ideally be achieved at a calculated travel length around the thread helix. In practice, the length of the transition thread profile is longer than the calculated ideal because it is not possible to achieve its ideal length using today's production and manufacturing methods. This anomaly results from two current situations: 1) the use of the thread rolling die itself must have its own construction tolerances, and 2) the use of a process that must allow for thread height tolerances.

[0021] Due to these limitations, the grooves in the thread rolling die that are actually utilized to form the transition thread profile on the thread helix must be longer and deeper than necessary to form a spiral ramp of the desired length on the fastener. This excess groove length in the die requires excess "space" in the die that is wasted because it is not utilized for the die to effect the required height change of the transition thread profile that it rolls during thread rolling. In essence, a linear transition that is longer than what is actually desired in the die thus results in a longer spiral transition being formed on the fastener helix.

[0022] The thread rolling die for an anti-crossing thread fastener can be formed by using a standard thread milling cutter to cut a series of linear grooves across the surface of the thread rolling die. When each individual cutter reaches a defined point, the cut surface is withdrawn from the workpiece (die) at a constant rate as the cutter continues to progress in a straight path across the die surface. The grooves, cut in the manner shown on the die surface, are linear with a constant depth over a finite length and then angled upward and out of the die. The angle formed at the bottom of the groove by withdrawing the cutter, in the manner shown, matches the desired growth rate for the transition thread profile to be formed within the fastener thread helix that the die will roll. The growth rate of the transition thread profile is shown as line 61, drawn across the upper portion of the thread segments illustrated in FIGS. 3A - 3H and 4A - 4H. The ideal linear angle at the bottom of the die groove produces a transition thread profile with a length of approximately 3 / 4 turn (270 degrees) of the helix when rolled on the fastener.

[0023] The angled portion of the groove in the die that forms the transition thread profile must, due to the tolerances of the thread rolling die itself and the thread height tolerance, actually be longer and deeper than the calculated ideal length of the transition thread profile. Using a longer and deeper groove in the die, the groove will not be completely filled with metal when forming the thread peak at its deepest point, and the groove will be narrower than the standard full thread over the entire length of the ramp in the die. These factors contribute to a transition thread profile that does not have the same width and fill as the slope of the standard thread. In particular, the transition thread profile helix, which is rolled onto the fastener by the die profile over the entire length of the ramp in the die groove, cannot technically engage the slope of the standard female thread. The desired height change can be achieved at the desired 3 / 4 turn (270 degrees) of the helix, but the transition thread profile continues for a distance beyond its length as a full height thread, but with a narrower slope compared to the fully standard thread. Thus, since the main purpose of the transition thread is to achieve a downward transition from the ISO type standard thread height to the anti-crossing thread height, the transition thread profile will have a certain portion of its length that is not required to achieve the height change.

[0024] Referring now to the drawings, the details of the exemplary embodiments are schematically illustrated. Like elements in the drawings will be represented by like numbers.

[0025] FIG. 5 illustrates a cross-sectional side view of a thread rolling die 60 and an anti-crossing type thread fastener 50. The cross-section is obtained by tracing the center of a thread rolling groove 63 within the thread rolling die 60. To illustrate the match between the die 60 and the fastener thread helix it rolls, the anti-crossing type thread fastener 50 is shown with its thread helix "linearized" such that both the linear die groove and the normally curved thread helix peaks appear as linear ramps rather than the curved helix actually seen on the fastener as it is rolled with the die. The thread rolling groove 63 has a constant depth section 64 and a ramp section 65. The thread rolling groove 63 transitions from the constant depth section 64 to the ramp section 65 at a transition point 66, and the ramp section 65 terminates at an end point (not shown) at its intersection with the cut anti-crossing type thread profile. The constant depth section 64 of the thread rolling groove 63 forms an ISO type standard thread profile 10 within the anti-crossing type screw fastener 50. The ramp section 65 of the thread rolling groove 63 forms a transition thread profile 20 within the anti-crossing type screw fastener 50. The length of the ramp section 65 extends well beyond the point where the fastener peak reaches the standard thread maximum height 16. The useless length 68 of the thread rolling groove 63 is "useless" because it is not filled with metal during rolling and leaves a gap 69. Thus, the useless length 68 serves no purpose other than to provide a tolerance space for forming an overfilled thread.

[0026] FIG. 6 shows a cross-sectional side view of a cutter tool 70 for cutting the thread rolling groove 63 in the die 60. Since the cutter tool 70 is used to cut a constant depth section 64 within the thread rolling groove 63 of the die 60 as shown in FIG. 5, it must have a longer point 71 compared to a cutter designed to cut a nominally formed thread having a shorter point 72. Further, when the cutting tool 70 is gradually inserted and cuts the ramp section 65, the cutter tool 70 is too thin and cannot cut the groove 63 in the die 60 with a width sufficient to form a full-width ISO type standard thread profile 10 until its cutting reaches the maximum depth within the die. Thus, the entire ramp section 65 of the groove 63 is cut in a state where it is too narrow with the cutter 71 to form a full-width ISO type standard thread profile 10.

[0027] FIG. 7A is a cross-sectional side view of an ISO type standard thread profile 10 being rolled by the die 60. FIG. 7B is a cross-sectional side view of a transition thread profile 20 being rolled by the die 60. For illustration, the standard thread profile 17 is superimposed on the die in FIG. 7B. Comparatively, the standard portion 21 of the transition thread profile 20 formed within the transition area of the die 60 is narrower than the standard thread profile 17 across the slope. In fact, this means that the length of the die occupancy area reserved for the transition thread to grow to its peak height, where its peak height 16 was actually within the acceptable height range of the standard thread peak, is wasted by rolling discrete portions of the transition thread that are too narrow to function as a full thread. Thus, there is a length of the thread helix rolled by the transition section of the die 60 between the actual ramp of the transition thread profile and the point where the thread reaches its full height and width for only the prior art manufacturing means. That transitional die groove length is necessary for the transition thread increase because the thread peak reaches the required height in the first portion of the groove, meets the minimum height requirement of the standard thread, and only the last section of the transitional groove form exceeds the minimum required height and is too narrow to be considered a full thread, forming a transition thread profile.

[0028] Figures 8A and 8B respectively show an end view and a side view of a conventional male anti-cross-thread fastener 50 having a long transition thread profile 20. The ISO type standard thread profile 10 of the helix is of full width and height up to the first change point 23 where the transition thread profile 20 begins. The transition thread profile 20 of the helix has a first section 24 between the first change point 23 and a second change point 25, where the outer profile of the thread has a height that exceeds the minimum required for a full standard thread but is too narrow to function as a full standard thread. At the second change point 25, the height of the transition thread profile 20 is reduced to the average standard thread height. In the second section 26, the helix profile is reduced in height and reaches the minimum standard thread height at point 27, but is still too narrow to function as a full standard thread. From the third change point 27, the transition thread profile 20 begins to have a lower height. Throughout the third section 28, the height and width of the transition thread profile 20 are steadily reduced until reaching the fourth change point 29. The fourth change point 29 marks the end of the transition thread profile 20 and the start of the anti-cross-thread profile 30. It should be noted that the anti-cross-thread portion 22 of the anti-cross-thread profile 30 demonstrates that the transition thread profile 20 is too thin over its entire length, including the first section 24, to perform the function of a full standard thread. Prior to the present invention, anti-cross-thread fasteners had a transition thread profile 20 of this length and included the "too narrow" first section 24 of the helix.

[0029] According to some embodiments of the present invention, the "too narrow" length of the transition thread profile 20 is eliminated, and a shorter anti-crossing thread fastener can be produced. To provide an anti-crossing thread fastener that is considered to be the shortest possible that is fully functional, i.e., at minimum cost, shortest, lightest, and most packageable, the "too narrow" length of the transition thread profile 20 can be eliminated. The design of the anti-crossing thread fastener according to the present invention can be based on providing a method of limiting the transition thread length actually required to achieve a gradual increase to the minimum acceptable peak height without accompanying non-functional "too narrow" sections. Some embodiments of the present invention include a novel profile for use on a portion of the helix of an anti-crossing thread fastener that enables reduction of the length of the transition thread without adversely affecting the thread function.

[0030] Some embodiments of the present invention provide a novel transition thread profile for an anti-crossing screw fastener, thus enabling the excess non-functional helix length to be excluded from that section of the thread helix. Such an improvement can be obtained by reconfiguring the first and second sections 24 and 26 of the transition thread profile 20 of the helix shown in FIGS. 8A and 8B.

[0031] These two sections of the transitional helix are herein reconfigured by reforming each length of the helix into a full standard width thread profile. The full width helix section will have a new variable but more precisely controlled peak height. In particular, the peak height is fully within the range of acceptable peak height values of the standard thread. According to an aspect of the present invention, the peak height value is carefully reduced in a controlled manner over the combined helix length of the two sections, i.e., the first and second sections 24 and 26, to the minimum acceptable standard thread profile height at the second change point 25 where the second section 26 blends into the start of the new shorter transition thread.

[0032] By reconfiguring these segments of the helix, the thread becomes, in effect, a "standard thread" such that the combined length of the first and second segments 24 and 26 is added to the existing standard thread helix, with the shorter segments of the helix reserved only for the transition function, resulting in a longer standard profile structure thread helix. This effectively enables shorter fasteners to perform the same function.

[0033] According to aspects of the invention utilized, the anti-cross-thread fastener described herein can provide a transition thread length that is approximately 1 / 4 turn (90 degrees) shorter than the previous ideal thread while maintaining the function of the previous transition thread's rate of descent. Even a slight reduction in the non-structural helix length of the fastener can provide a significant advantage in the function of the fastener. Thus, various aspects of the invention can provide a shorter, lighter, lower-cost, more packageable fastener with improved anti-cross-thread functionality.

[0034] Referring to FIG. 9, a cross-sectional side view of the transition thread profile 120 of the present invention is shown. The transition thread profile 120 has a thread height 118 that is significantly shorter than the height that could be considered as the standard thread major diameter 116. The standard thread major diameter 116 can be formed by completely filling the die at an appropriate average position to meet the standard thread requirements. The transition thread profile 120, having a relatively shorter thread height 118, maintains all the characteristics of the standard thread except for the height. Since the thread height 118 of the transition thread profile 120 is more precisely controlled, the thread does not need to be maintained within the same significant tolerance range, and while maintaining its full width and flank angle and providing fastening characteristics, it may be made shorter to reduce the localized peak height to a more useful height. This relatively shorter thread height 118 can enable the transition thread profile 120 of the helix to start at a lower height.

[0035] This very localized and careful reduction at the thread peak height, assuming it is only localized, will give the manufacturer the freedom to vary the standard thread peak height in all sections, except for the sections utilized for another purpose of the transitional threads, with the remainder of the standard thread helix remaining at full height and full tolerance, as may be required by the manufacturer's process and / or customer requirements.

[0036] According to an aspect of the invention, a standard type anti-crossing thread rolling die may comprise a reduced depth section within the die groove that is always preferentially and fully filled. FIG. 10 is a cross-sectional side view of three threads of a fastener 150 being rolled in three adjacent grooves of a die 160 to form a standard thread having a major diameter at the upper major diameter limit 115. In the first groove, the thread material of the fastener is pressed into the shorter and more restrictive groove, has a more restricted shape, and fills the groove completely into a thread profile having a height at the lower major diameter limit 116. In the second groove, the thread material of the fastener is pressed into the full depth groove and partially fills the groove up to the mean major diameter limit 114. In the third groove, the thread material of the fastener is pressed into the full depth groove and fills the groove up to the upper major diameter limit 115 having a maximum allowable height. During the thread rolling process, the metal flow is restricted within discrete sections of the helix, and the remaining full thread helix length is underfilled to a variable extent within its allowable height range, i.e., between the lower major diameter limit 116 and the upper major diameter limit 115, enabling the individual manufacturer's requirements for the full thread height of the standard thread having a major diameter to be met without affecting the rolling process or the function of the structural thread in any way. Such preferential filling of the sections utilized for another purpose of a thinner profile can also occur when the adjacent full standard thread helices are manufactured with their peaks associated with the lower major diameter limit 116.

[0037] An aspect of the present invention provides a carefully localized reduction of thread height within an area adjacent to the transition thread, which shortens the "ramp" required to reach the peak of the anti-crossing thread fastener, effectively providing a shorter transition thread and enabling an anti-crossing thread fastener with a reduced length. A portion of the thread helix on a male anti-crossing screw fastener of the type discussed above may be contoured to shorten the effective length of the helix of the anti-crossing thread fastener. The transition section of the helix may be no longer than one turn (360 degrees) of the thread helix and may start at the end of the standard turn of the fastener helix at the point on the outermost standard turn farthest from the head of the fastener and may end with an anti-crossing thread.

[0038] The transition thread profile according to an aspect of the present invention may be contoured such that its highest point blends with the standard thread of the full height of the helix. From there, the transition thread profile section of the helix may be reduced in height at a defined rate to its shortest point as it wraps around the fastener shaft. The transition thread profile starts at the point where the nominal full height major diameter of the standard thread helix first reduces in height, blends through approximately 1 / 4 turn (90 degrees) of the helix, and continues to reduce the thread height while maintaining a slope similar to the standard thread, while maintaining the slope width and thread angle consistent with the standard thread profile and always at a height approximately equal to the acceptable minimum for a full standard thread defined as the lower major diameter limit 116.

[0039] The full standard thread section of the helix can thereby provide a similar length of functionally equivalent threads, and the transition section of the helix can thereby be reduced in length by an equivalent amount. The male anti-crossing screw fastener may have appropriate anti-crossing screw features adjacent to the leading end of the transition thread, as well as appropriate leading threads and guiding features at the point of the fastener. It is expected that this structure can also be utilized on other types of fasteners and on anti-crossing screw fasteners with shorter, i.e., quasi-ideal length, transition threads to improve their function.

[0040] Referring to FIGS. 11A and 11B, an end view and a side view of the male anti-cross-thread fastener of the present invention are shown. The helical ISO type standard thread profile 110 has a full standard thread width and height up to a first change point 123. At the first change point 123, the helical thread has having a maximum allowable height, of the upper large-diameter limit a standard thread height, a full standard thread flank width, and a thread angle of 60 degrees. (See 115 in FIG. 10). This flank width and peak height are maintained up to a second change point 125 throughout a first section 124. Over a second section 126 from the second change point 125 to a third change point 127, the helical profile is preferably reduced at a constant rate to an average major diameter limit 114 (see 114 in FIG. 10) for the standard thread height (minimum acceptable) at the third change point 127. Throughout the second section 126, the flank width of the slope is maintained as its standard fastener profile. As shown in FIG. 11B, the top of the thread grows wider from the second change point 125 to the third change point 127 throughout the second section 126. Also, as shown in FIG. 11B, the flat slope of the thread is maintained in the valley from the second change point 125 to the third change point 127 throughout the second section 126.

[0041] Referring further to FIGS. 11A and 11B, a third section 128 extends from the third change point 127 to a fourth change point 129. At the third change point 127, the thread profile is reduced to its minimum height and is that of the standard thread 110 maintained at the standard flank width. The transitional thread profile 120 starts from this profile at the third change point 127 and transitions until it takes on the anti-cross-thread profile at the fourth change point 129. The transitional thread profile 120 can start from the third change point 127 and end at the fourth change point 129 so as to wind around the shaft portion 14 over about 5 / 8 turn (225 degrees).

[0042] Figures 12A and 12B show an end view and a side view of a male anti-cross-thread fastener. In this embodiment, the fastener thread has a maximum material condition, where the thread peak is at its highest value relative to the pitch line, meaning that the groove in the die that forms such a peak will be completely filled with material. The notable difference between this embodiment and what is shown in FIGS. 11A and 11B is that the full thread height is not the higher standard thread height (see 115 in FIG. 10), but rather the limited lower maximum allowable height at the first change point 123 within the helical thread (see 116 in FIG. 10). Under the limited maximum material condition, the peak would be expected to flow to the maximum allowable height within the mating die groove. Instead, the thread peak is carefully controlled to be shorter than the expected flow height, and this controlled height drops to the average height peak at a constant preferred rate while maintaining the full slope width. This difference in thread tolerance and manufacturing results in a constant growth of the transition helical section through the third section 128 rather than a constant height through the first section 124 (see FIG. 11A). This variation in height demonstrates the "free flow" of the metal to this height within the fastener that utilizes the extreme major diameter.

[0043] As can be seen from a comparison of the drawings (FIGS. 11A-11B and 12A-12B), the length of the virtually full standard thread is increased by reconfiguring the first section 124 and the second section 126 to be full-width threads while maintaining the full length of the fastener helix.

[0044] Figure 13E is an end view of a male fastener taken along the contour of a transition thread, and Figures 13A - 13D are cross-sectional side views of the transition thread obtained in the section shown in Figure 13E. The transition thread contour 120 has a width that is the same as the outer shape of a standard thread while gradually reducing the peak height from the maximum allowable value for the standard thread to the minimum allowable value. As shown in Figures 13A - 13D, the width of the transition thread contour 120 remains constant and is the same as the outer shape of the standard thread. As shown in Figure 13D, the transition thread contour 120 has a height 118 that is the same as the upper major diameter limit 115. See 115 in Figure 10. As shown in Figure 13C, the transition thread contour 120 is shorter and has a height 118 that is not as high as the maximum allowable value for the standard thread 115. As shown in Figure 13B, the transition thread contour 120 is shorter and still has a height 118 that is not as low as the average major diameter limit 114 for the standard thread. See 114 in Figure 10. As shown in Figure 13A, the transition thread contour 120 has a height 118 that is approximately equal to the minimum acceptable value for a full standard thread defined as the lower major diameter limit 116. See 116 in Figure 10.

[0045] Since the transition thread contour 120 has a slope with the same width as the standard thread, the length of the ISO type standard thread portion of the helix can be shortened. In particular, only the length of the transition thread contour 120 from the first change point 123 to the third change point 127 can be shortened. This portion of the transition thread contour 120 replaces a section that was previously functionally unnecessary and is here considered a standard thread, making it possible to add the usable length to the standard thread helix. Thus, additional full threads may be utilized in the mating joint design being fastened, or alternatively, the overall length of the fastener can be reduced by shortening the standard thread by the amount of the added low-profile standard thread, and thus the weight and cost may be reduced.

[0046] The transition thread profile 120 of the present invention carefully provides the reduced diameter section of the fastener blank to the rolling die, allows the free flow of the metal, and to achieve the desired shape, during rolling, by underfilling specific localized sections of the thread rolling die with metal, may be manufactured as part of the thread helix of a male cross-preventing thread fastener. Alternatively, the transition thread profile 120 may be machined to a lower height in some local areas of the helix. Either method may create a reduced height section of the full width of the helix.

[0047] Embodiments of the present disclosure are depicted, described, and defined with reference to exemplary embodiments of the present disclosure, but such reference does not imply limitations with respect to the present disclosure, nor are such limitations to be inferred. The disclosed subject matter is capable of numerous modifications, variations, and equivalents in form and function, as will occur to those skilled in the art and those having the benefit of the present disclosure. The embodiments described and depicted in the present disclosure are merely examples and not an inclusive scope of the present disclosure.

Claims

1. A male-type cross-preventing screw fastening device, comprising a shaft portion, wherein the shaft portion has a leading end, a torque end, and a plurality of male threads around the circumference of the shaft portion, wherein the plurality of male threads are standard threads that are around at least a part of the circumference of the shaft portion and have a standard thread profile, wherein the width and thread angle of the standard threads enable engagement with corresponding female threads, the major diameter of the standard threads is at an upper major diameter limit having an upper limit value of the standard thread height, the standard thread profile includes a section where the width and the thread angle of the standard threads are maintained and the height decreases from the upper major diameter limit of the standard threads to an average major diameter limit, and the average major diameter limit has an average value of the upper limit value and the lower limit value of the standard thread height, a standard thread, transition threads that are around at least a part of the circumference of the shaft portion, cross-preventing threads that are around at least a part of the circumference of the shaft portion and have a cross-preventing thread profile and an outer diameter configured to facilitate alignment of the male-type cross-preventing screw fastening device and a female fastening device, and leading threads that are around at least a part of the circumference of the shaft portion and have a leading thread profile, and is provided with, wherein the transition threads have a transition thread profile that starts with the same width and thread angle as the width and thread angle of the standard threads that enable engagement with corresponding female threads, transitions to the cross-preventing thread profile, and the transition thread profile has a height that transitions from the average major diameter limit of the standard threads to the outer diameter of the cross-preventing threads, a male-type cross-preventing screw fastening device.

2. The cross-preventing screw fastening device according to claim 1, wherein the standard threads are wound around the shaft portion for at least two turns (720 degrees).

3. The cross-preventing screw fastening device according to claim 1, wherein the transition threads are wound around the shaft portion for less than 5 / 8 turn (225 degrees).

4. The cross-preventing screw fastening device according to claim 1, wherein the cross-preventing threads are wound around the shaft portion for 1 turn (360 degrees) to 2 turns (720 degrees).

5. The cross-preventing screw fastening device according to claim 1, wherein the leading threads are wound around the shaft portion for 1 / 2 turn (180 degrees) to 2 turns (720 degrees).

6. The standard thread has a thread angle of 60 degrees, and the transition thread has a thread angle of 60 degrees from the root to the crest. The anti-crossing screw fastening device according to claim 1.

7. The transition thread profile has a crest that widens as the height transitions from the average major diameter limit of the standard thread to the outer diameter of the anti-crossing thread. The anti-crossing screw fastening device according to claim 1.

8. The outer diameter of the anti-crossing thread is the same as the pitch diameter of the standard thread, and the anti-crossing thread profile has a shape defined by a curve extending from the curve at the root to the outer diameter. The anti-crossing screw fastening device according to claim 1.

9. The standard thread, the transition thread, the anti-crossing thread, and the leading thread have a continuous thread helix around the shaft portion. The anti-crossing screw fastening device according to claim 1.

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