HK1246841B - Male anti-false thread fastener member - Google Patents

Description

Convex anti-wrong-tightening fastening component

Technical Field

The present invention relates generally to the field of threaded fasteners such as screws and bolts, and more particularly to preventing mis-torquing of fasteners.

Background Art

Threaded fastener technology is fundamental to the construction or fabrication of most manufactured items, such as machines, automobiles, trains, airplanes, engines, and the like. A threaded fastener may be a bolt, screw, stud, rod, or other generally circular component having a uniform, non-uniform, or tapered external helical thread that is tightenably engaged in a mating threaded fastener (e.g., a nut or hole having a generally matching internal helical thread). For proper engagement of an externally threaded fastener with an internally threaded fastener, the longitudinal axis of the externally threaded component must generally be generally colinear with the longitudinal axis of the internally threaded component. Furthermore, proper engagement of an externally threaded fastener with an internally threaded fastener generally requires that the peaks of the external threads of the male helix be aligned with the roots of the internal threads of the mating female helix. While the present invention relates to any thread form, the International Organization for Standardization (ISO) metric thread will be illustrated as an example of a standard thread, as shown in FIG1 . As used in this application, the designation "thread" may apply to the entire fastener thread helix, or any partial segment of the helix, where the thread may include a partial turn or turns around the shank of the fastener in the case of a male fastener component, or a partial turn or turns around the internal bore in the case of a female fastener component.

The inability to achieve proper threaded engagement between an externally threaded fastener and an internally threaded fastener during assembly is typically caused by one of two threading conditions that occur when opposing helices engage and partially rotate relative to each other. The first threading condition, often referred to as "cross threading," occurs when there is both angular and linear axial misalignment between an externally threaded component (usually a bolt or screw) and an internally threaded component (usually a nut or threaded hole). Specifically, cross threading is the result of two components attempting to engage at least half a thread pitch away from linear alignment when the respective helices are also angularly misaligned.

FIG2 illustrates a cross-threaded male and female fastener components. When the fastener components are cross-threaded, the male fastener component 10 is not co-linear with the female fastener component 30, and the threads become wedged as the threaded helices rotate against each other. If rotation continues while the threads are in this wedged condition, the threads of one or both components will typically become structurally damaged.

The second threading condition that prevents proper thread engagement is commonly referred to as "misthreading," which occurs when the two helices are out of alignment by half a thread pitch, such that the threads engage crest to crest rather than crest to root.

Figures 3A and 3B illustrate a mis-tightening situation in which the helix axes are not misaligned, but rather they are substantially colinear. Internal threads are typically manufactured with a slight depression, groove, or fissure 32 at the crest of the internal thread. Mis-tightening occurs when the crest of the external leading thread 17 engages the groove 32 at the crest of the internal thread, causing the two helices to deviate from alignment by half a pitch. Figure 3B is a close-up view of the mis-tightening situation of Figure 3A and illustrates how such a groove 32 at the crest of the internal thread (although it is typically smaller in the main body of the internal thread helix) can be slightly deeper and wider in the entry end of the helix—the leading thread section of the internal thread. In this case, it is possible for the peak of the leading thread 17 (and/or the first full thread of the helix) of the external thread helix to attempt to enter the normal helix root in the opposing internal helix, but instead engages the internal thread helix at the groove 32 in the crest of the internal thread helix.

Several characteristics of the leading threads of currently widely manufactured internal helices significantly increase the likelihood of mis-tightening failures.

First, Figures 4A to 4F illustrate how a typical internal guide thread 31 of a female fastening component 30 tends to have depressions, grooves, or fissures 32 at its crests, which tend to cause incorrect screwing failures. These grooves 32 can be deep and wide at the entry end of the helix. As the grooves 32 advance into the internal helix away from their starting point, they tend to narrow and become shallower, and in most fasteners, they largely disappear within about half a revolution of the internal helix. Thus, the surface forming the deepest point in the groove 32 tends to distance itself from the axis of the internal thread helix at a faster rate as the grooves 32 in the internal guide thread 31 approach and approach the full thread.

Second, Figures 5A-5B illustrate two side views of a male fastening component 10 having a fastening thread 15, wherein the lead thread 17 may have a generally pointed tooth profile and/or have some type of protruding feature at its peak, which tends to lead to mis-tightening failures. Figure 6 shows a side view of a male fastening component 10 having a fastening thread 15 and a cross-threading prevention thread 16, wherein the lead thread 17 has a typical tooth profile with a pointed peak. Figure 7 shows a side view of a male fastening component 10 having a fastening thread 15, a cross-threading prevention thread 16, and a stop point 22, wherein the lead thread 17 has a typical tooth profile including a combination of a curved surface and a flat surface with a pointed peak. Mis-tightening failures may occur when the pointed peak of the lead thread of the male fastening component engages a groove in the tooth crest of the internal thread illustrated in Figures 4A-4F.

Third, the relative helix angles of the peaks at the crests of the internal and external guide threads can cause mis-screwing failures. Internal and external guide threads tend to have different helix angles due to their respective manufacturing methods. If the helix angle of the external thread peak of the guide thread is greater than the helix angle of the internal peak of the guide thread, the external peak is more severely curved. This means that during initial assembly, when the two guide threads come into contact, their peaks are essentially non-parallel. The more severely curved thread (i.e., the thread with the larger helix angle) will tend to approach the other thread or intersect with the other thread at one point on the thread. At the intersection point on the thread, the pointed peak of the external guide thread may enter the groove in the crest of the internal thread to cause a mis-screwing situation. Other orientation situations in which the axes of the two threads are not colinear can also lead to mis-screwing failures.

When these characteristics, individually or in combination, exist to allow the pointed peak of the external lead thread to inadvertently enter a groove in the crest of the internal lead thread, the external peak can behave as if it were screwed into a normal internal thread. Since there is no path out of the groove, the point of the external lead thread can continue to follow the groove as the fastening components are rotated relative to each other.

However, the grooves narrow and close together very quickly (as shown in Figures 4A through 4F), leaving no path for the external thread's pointed crest to continue turning. The helix angle of the line formed at the bottom of the groove in the internal guide thread is typically slightly greater than the helix angle of the line formed at the pointed crest of the external thread. Because these lines are not parallel (i.e., the helix angles are different), the threads intersect quickly, and the pointed crest of the external guide thread quickly contacts the surface in the groove in the internal thread's crest. As a result, the pointed guide thread of the external fastener can only rotate freely for a few degrees before it grows too large for the shrinking groove in the internal thread's crest, leaving no path for the pointed guide thread to continue turning. This engagement often causes the pointed crest of the external thread to embed or jam in the groove in the internal thread's crest. Continued relative rotation of the fastener components beyond this incorrect tightening point often damages or scrapes off a portion of either thread, leading to structural failure of both thread helices.

Furthermore, many currently manufactured external lead threads have a shape that causes them to exhibit a bump or sudden increase in height, particularly when the lead thread is very low. If the lead thread length is less than half the pitch (less than 180° around the shank), the lead thread can increase in height rapidly and is therefore more susceptible to mis-threading. When an external lead thread with a bump or sudden increase in height is screwed into a groove in the crest of an internal thread, a mis-threading failure can occur, as described above.

Various types of guide threads are used in industry today. In all areas of threaded fastener technology, with the exception of self-tapping screws, guide threads are used to feed, or "guide," the external thread helix into the space between adjacent turns of the internal thread helix. In practice, several guide thread shapes have been utilized for this purpose. The most common of these guide thread shapes, used on most standard threaded fasteners, is a guide thread arrangement that traditionally utilizes a portion of the first turn of the helix to grow from zero height to full thread height while simultaneously growing wider in width. During a typical manufacturing process, this guide thread is allowed to take any free-form shape that allows it to be easily manufactured. This shape typically consists of a 60-degree flank on the side of the helix closest to the fastener head and a free-form flank on the side farthest from the fastener head. The profile of the guide thread varies significantly during the manufacturing process and from fastener design to fastener design. Due to the inherent variations in the manufacturing methods used to thread roll this guide thread segment, the shape of this segment is often inconsistent in form and unpredictable in its growth rate. The change in shape and linear growth is most apparent in the ridge formed at the peak of the external lead thread. (See Figures 5A and 5B.) Typical lead threads typically have a relatively sharp point at the crest of the lead thread because only one flank has a flat surface at a standard 60° angle, while the opposing flank surface is free-form at an angle much greater than 60°, and the two flanks are connected directly to each other rather than through a flat surface parallel to the longitudinal axis of the fastener shank (as with other standard threads).

One "non-standard" fastener includes anti-cross-threading threads, which are more fully described in U.S. Patent No. 5,730,566, which is incorporated herein by reference in its entirety. These non-standard fasteners include three threads: a guide thread 17, an anti-cross-threading thread 16, and a fastening thread 15. (See FIG6 ). The typical guide thread on a fastener with an anti-cross-threading thread differs slightly from the guide thread on a standard fastener, but is only subject to variations in thread form and length. The thread form of a typical guide thread of a fastener with an anti-cross-threading thread has three common characteristics within each segment of the guide thread helix.

First, as shown in FIG7 , the leading thread flank 17b closest to the anti-cross-thread thread 16 tends to maintain a curve that is not half (or less) different from the curve seen in the anti-cross-thread thread 16, but is essentially a mirror image of half of the anti-cross-thread thread 16. The base of this curved leading thread flank 17b shares its root with the anti-cross-thread thread 16. As such, its root appears as a continuation of the anti-cross-thread thread root, and half of the leading thread profile appears as the anti-cross-thread thread profile. As this flank approaches the end of the helix, the curved surface becomes increasingly narrower, ultimately disappearing at the end of the helix as the leading thread reaches zero height. The other leading thread flank 17a tends to be essentially flat and angled with the fastener axis, with angles and flatness, as well as convexity and concavity, often varying significantly and freely in each section depending on the location on the helix and the manufacturing technique. Typically, the angle, convexity, or concavity of this flank is not controlled during manufacturing and varies significantly in angle, growth rate, and profile throughout the length of the leading thread. As the lead thread traverses around the body, this "flat" flank 17a tends to narrow and decrease in height. This "narrowing" is the result of the root of the flat-angled flank moving closer and closer to the root between the lead thread 17 and the anti-cross-threading thread 16 as the lead thread 17 traverses around the shank. Ultimately, this flat-angled flank 17a narrows to zero as the height and width of the lead thread 17 decrease toward the end of the helix. Therefore, because this pointed peak of the lead thread is typically formed from unrestricted, free-flowing metal, it tends to vary significantly in shape throughout the length of the lead thread and from fastener to fastener.

Third, the flanks of the leading thread 17 tend to form a point at the intersection of the two flanks rather than a flat or curved crest.

Figures 8A through 8C illustrate cross-sectional side views of a typical process for manufacturing a fastener from an unthreaded fastener blank by rolling the unthreaded fastener blank between opposing thread rolling dies. In Figure 8A, the thread rolling die 40 is isolated to illustrate the placement of the fastener blank 41 prior to rolling. The shank 12 of the fastener blank 41 typically has a constant diameter to allow for the formation of standard threads, and the leading end 14 of the unthreaded fastener blank typically has a chamfer 9 to allow for the formation of leading threads. Figure 8B shows the thread rolling die 40 in a rolling position such that threads are formed on the fastener blank to form a male fastening component 10. In typical manufacturing practices for both standard and cross-thread proof thread fastening, threads are formed by rolling a substantially cylindrical unthreaded fastener blank 41 through a thread rolling die 40. The die 40 imparts the thread profile to the unthreaded blank 41 by displacing metal into grooves formed in the thread rolling die. As shown in FIG8C , a fastening thread 15 can be formed on a constant diameter shank portion of an unthreaded fastener blank by allowing metal to flow into the grooves of the die until the grooves are completely filled with metal from the blank. The fastening thread 15 formed on the shank of the fastener tends to have a completely uniform profile because the metal completely fills the grooves in the die. However, a leading thread 17 can be formed by incompletely filling the grooves of the rolling die 40 with metal from the chamfered end of the fastener blank. In the leading thread section of the fastener, the thread helix is formed by only partially filling the grooves in the rolling die. Partial filling occurs because the fastener blank has a chamfer at its end, as shown in FIG8A .

FIG8C illustrates a close-up view of the lead thread section shown in FIG8B . Because the unthreaded fastener blank has a chamfer at its end, there is not enough metal in the lead thread area to completely fill the grooves in the thread rolling die 40. Lead threads 17 for both standard fasteners and cross-threaded fasteners are formed by partially filling the die grooves in the lead threaded section. Partial filling allows metal to flow freely into a variety of lead thread profiles, as described above. Therefore, lead thread profiles are inherently inconsistent due to variations in the blank, die, and process. In most known lead threads, variation is inherent because the thread rolling die allows unrestricted, free-flowing metal to adopt a variety of lead thread profiles.

Some guide thread profiles are particularly susceptible to mis-threading. In some cases, the guide thread profile varies too much over the length of the guide thread to cause mis-threading. For example, the guide thread may increase in height too quickly, i.e., it grows from the shank to the full height of the standard thread in less than 180° around the shank. For another example, the angle of the leading flat angle flank of the guide thread may be too steep to allow proper mating with the female thread. As yet another example, the guide thread profile may be severely pointed, which may lead to possible mis-threading and/or inadvertent and undesirable contact with the internal female thread during initial threading. For cross-threaded fasteners, some guide thread profiles may cause the cross-threaded fastener to be mis-threaded into the internal female thread before the cross-thread has a chance to align the fastening components for proper threading. Some lead thread profiles cause the internal and external threads to contact each other in an undesirable position on their respective helical lines before the cross-threading thread acts on the internal thread to align the fastening components, thereby hindering and/or preventing the cross-threading thread from acting as a cam on the internal lead thread of the female fastening component. This may be particularly true when the initial angular misalignment of the two fastening components is high. In addition, many lead thread profiles on the external male fastening component may engage the groove in the internal female guide, leading to a mis-threading condition, as described above.

Some lead threads used on cross-threaded fasteners have a steep helix angle, so that the lead thread grows from zero height to the cross-threaded height within only 270° around the shank. The peak of a low lead thread such as these can engage a groove in the lead thread of an internal female fastener and/or a smaller groove in the internal full thread, leading to misthreading.

In still other guide threads used on cross-threaded fasteners, the width of the guide thread profile is constantly maintained, similar to the width of a standard thread, as the height of the guide thread increases over the length of the guide thread. These guide threads tend to have a different profile in each section of the guide thread. They tend to have a very flat curve near the beginning of the guide thread and a gradually tapering, tapering profile as the guide thread helix gradually merges into the cross-threaded thread profile. As the guide thread grows in height, these guide threads tend to embed into the groove at the tip of the inner concave guide thread, which can lead to misthreading.

Therefore, there is a need for an external lead thread for a male fastener component that tends to prevent the lead thread from being misthreaded into a groove in the peak of the internal thread of a female fastener component. The lead thread should not be subject to manufacturing variations that would result in undesirable localized lead thread height and profile, as well as large helix angles. For cross-threaded fasteners, there is a need for a lead thread that facilitates, rather than hinders, the performance of the cross-threaded thread.

Summary of the Invention

Fasteners, fastener systems, and methods for preventing or inhibiting mis-tightening are disclosed.

One embodiment of the present invention provides a male, anti-error-tightening fastener component having features comprising: a shank having a leading end and a tool engaging end; a head formed at the tool engaging end of the shank; at least one male fastening thread formed on an exterior of the shank as a plurality of thread turns adapted to mate with a corresponding female fastening thread formed in an interior of a female fastener component; and at least one male guide thread formed on the exterior of the shank at the leading end, the at least one male guide thread being at least half a turn around the shank and comprising a curved profile defined by an arc having a radius approximately equal to a radius of the arc tangential to both flanks of the thread profile of the at least one male fastening thread and located below a pitch axis of the at least one male fastener thread.

18. The screw thread assembly of claim 17, wherein the threaded portion is threaded and secured to the tool holder's body for engagement with the threaded portion. The threaded portion is threaded and secured to the tool holder's body for engagement with the threaded portion.

18. The screw thread assembly of claim 17, wherein the threaded portion is configured to engage a threaded portion of the tool and to engage a threaded portion of the tool. The threaded portion is configured to engage a threaded portion of the tool and to engage a threaded portion of the tool.

The above and other preferred features, including various novel details of implementation and combination of elements, will now be described in more detail with reference to the accompanying drawings, and pointed out in the claims. It will be understood that the specific methods and circuits described herein are shown by way of illustration only and are not intended to be limiting. As will be understood by those skilled in the art, the principles and features described herein can be used in various and numerous embodiments without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the presently disclosed systems and methods and, together with the general description given above and the detailed description of the embodiments given below, serve to explain and teach the principles of the present fasteners, fastener systems, and fastener methods.

1 illustrates a side view of a prior art male fastener component having a standard thread, wherein several portions of the standard thread are identified, including the crest, flank, root, pitch, thread angle, minor diameter, and major diameter.

2 illustrates a side view of prior art male and female fastening components having misaligned longitudinal axes, a condition of possible cross-threading utilizing prior art fasteners.

3A and 3B show side views of prior art male and female fastening components that are translationally misaligned relative to one another such that an offset thread pitch results in possible mis-torquing of the fastener, with FIG. 3B being a close-up view relative to FIG. 3A .

4A-4F illustrate cross-sectional side and end views of a prior art female fastening component having female guide threads in its interior with grooves in its crests.

5A and 5B show side views of a prior art male fastening member having pointed guide threads.

6 illustrates a side view of a prior art male fastener component having pointed guide threads fused into anti-cross-threading threads.

7 shows a side view of a prior art male fastener component having a lead-in point and pointed guide threads that merge into anti-cross-threading threads.

8A-8C show side views of a prior art fastener blank being rolled between dies and illustrate how lead threads are typically formed on a fastener by allowing metal of the fastener blank to only partially fill grooves in the dies so that the lead threads are free form.

9A and 9B (with FIG. 9B being a close-up view) illustrate side views of a male fastening component of the present invention having a head and a shank with the shank having fastening threads, anti-cross-threading threads, and guide threads in the same helix.

10A-10E illustrate cross-sectional side and end views of a male fastening component of the present invention having anti-cross threading threads and leading threads in the same helix, wherein the leading threads are anchored to the anti-cross threading threads.

1 IA-HE illustrate cross-sectional side and end views of a male fastening component of the present invention having fastener threads and guide threads in the same helix with the guide threads anchored to the next winding.

12A-12E illustrate cross-sectional side and end views of a male fastening component of the present invention having anti-cross-threading threads and guide threads in the same helix, wherein the guide threads are not anchored to the anti-cross-threading threads and are located in the middle of the fastening thread profile.

13A-13E illustrate cross-sectional side and end views of a male fastening component of the present invention having fastener threads and guide threads in the same helix, wherein the guide threads are not anchored to the next winding and are as far away from the next winding as possible while still within the fastening thread profile.

14A-14E show cross-sectional side views of the male fastening component of the present invention inserted into a female fastener, with the male lead threads of the male fastening component overriding grooves in the crests of the female lead threads to inhibit or prevent mis-threading.

14F is a side view of a female fastening component having guide threads.

15A-15C show side views of a male fastening member of the present invention having a lead-in point at the leading end of the shank.

16A-16D illustrate cross-sectional side views of a male fastener having an introduction point.

The figures are not necessarily drawn to scale, and for illustrative purposes, similar reference numbers generally represent elements of similar structure or function throughout the figures. The figures are intended only to facilitate the description of the various embodiments described herein. The figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims.

DETAILED DESCRIPTION

In accordance with the teachings of the present invention, the present invention satisfies the aforementioned needs and further overcomes other shortcomings and deficiencies of prior fastener technology by providing a novel starting point for a thread helix (otherwise referred to as a 'lead thread' of a threaded fastener), a misthreading of the aligned lead thread (whose unique profile prevents it from penetrating deeply into and/or remaining in any groove present in the lead thread's peak), and/or a full thread of the internal thread helix of a female fastening component. The lead thread with the misthreading profile can be present on a fastener for approximately one and one-fifth turns of the helix, wherein the lead thread maintains substantially the same broad, curved peak profile in each axial segment of the lead thread.

Figures 9A and 9B illustrate one embodiment of the present invention, with Figure 9B being a close-up view of the leading end portion of the fastener shown in Figure 9A. As shown in Figures 9A and 9B, the fastener includes both anti-cross-threading threads and leading threads to prevent incorrect threading. The male fastening member 10 of this embodiment is a bolt or screw having a helical thread 11 that is externally wound around the shank 12 of the male fastening member 10. A head 13 is formed at one end of the shank 12 of the male fastening member 10 and is adapted to be engaged by a member for applying rotational torque. The head 13 may be slotted to accept a flat, Phillips, Torx, or similar screwdriver, or may have multiple surfaces for engagement by a wrench, socket, Allen key, or other member for rotationally engaging the head. The head 13 may take any form known in the art for imparting rotational engagement to the fastener. The male fastener shank can also be connected to a portion of the device to be fastened (e.g., by welding or other means) such that the female fastening member can be rotationally screwed onto the male fastener shank for fastening. In this case, the feature connected to the portion of the device to be fastened is the head of the male fastening member.

The helix of thread 11 wound around shank 12 of male fastening component 10 can adopt several distinct profiles over the length of the helix as it progresses from head 13 around shank 12 to leading end 14 of the fastener. These diverse thread profiles are discussed with reference to Figures 9A and 9B. Adjacent to head 13 may be several turns of fastening thread 15, such as are present on standard fasteners (see Figure 1). As helix 11 winds away from head 13, these threads may be followed by a low section of anti-cross-threading thread 16, where fastening thread 15 merges into anti-cross-threading thread 16 on the same helix 11. Anti-cross-threading thread 16 has a profile that imparts anti-cross-threading functionality to that section of the helix because at least a portion of one turn of the thread helix has a transitional curved surface from minor diameter to major diameter. A detailed description of anti-cross-threading thread 16 is provided in U.S. Patent No. 5,730,566, which is incorporated herein by reference in its entirety. The anti-cross-threading thread 16 can be followed by a pilot thread 17 on the helical line 11. All of these thread profiles, regardless of their specific localized shape and profile, are contained within the envelope defined by the profile of the fastening thread 15.

In an alternative embodiment of the male fastening component, the helix of the thread 11 comprises the fastening thread 15 and the guide thread 17 without cross-threading prevention threads, so that the fastening thread 15 merges directly into the guide thread 17 .

9B , the guide thread 17 begins at a location on the helix 11 where it joins the anti-crossthreading thread 16 at a fusion point 18 and extends one and a fifth turns around the helix 11 to reach a helix termination point 19. At the fusion point 18, the guide thread 17 reaches its highest (or tallest) point (as measured from the thread axis) and has a height and profile that matches the height and profile of the anti-crossthreading thread 16. From the fusion point 18, the guide thread 17 follows the helix 11 for one and a fifth turns around the male fastening component 10 and away from the head 13 until it ends at the helix termination point 19. As the guide thread winds around the fastener body toward the leading end 14 of the male fastening component 10, the height of the guide thread (as measured from the root of the fastening thread 15) decreases at a substantially constant rate throughout its length. In one embodiment, the rate of decrease in the height of the guide thread 17 is not significantly greater and not significantly less than the rate of decrease calculated by utilizing the length of approximately one and one-fifth turns of the helix until the height and width of the guide thread reach essentially zero (minimum diameter) at the helix termination point 19 at the root height of the fastening thread 15.

From the leading end 14 of the male fastening component 10, the guide thread 17 may begin at zero height on a cylinder having a diameter defined by the roots of the fastening threads 15. The apex of the guide thread crest may begin at the standard thread root height, and then as the guide thread winds around the body of the fastener toward the head 13, the crest of the guide thread may deviate from the root height and the axis of the fastener's helix at a constant rate, such that the crest grows in height from essentially zero at its starting point to a height just less than the pitch diameter of the standard thread at the fusion point 18 (which is approximately the height of the anti-cross-thread thread 16). During this increase in height, the width of the guide thread profile gradually increases as the guide thread advances around the body of the fastener.

In one aspect of the present invention, the anti-mis-tightening guide thread can be shaped so that the height of the thread increases at a specified maximum constant rate as the thread progresses around the fastener body from the start of the helix to the point where the thread merges with the next section of the helix. In alternative embodiments, the guide thread can extend around the shank for any number of turns of the helix, as long as the rate of increase does not present a steeper point at the crest of the guide thread (which can be mis-tightened in a female fastener component). The rate of increase can be such that the included spiral taper angle of the peak end of the external guide thread profile is consistent and does not present severely angled surfaces, bumps, sharpness, or other inconsistent features that can easily enter any groove in the peak end of the guide thread of a normal internal thread helix when the external guide thread is presented to receive an internally threaded component at any normal assembly angle. In this way, when the peaks of the corresponding ridges forming the mating guide threads of the two components contact at any point during assembly, the height of the peak of the outer fastener does not increase at a rapid rate that causes the peak to grow into any groove in the inner peak before the two peaks slide over each other (due to the axial load applied by the installer) (and prevent the two thread helices from advancing further into each other). The outer guide thread profile allows the two guide threads to contact each other and then slide over each other without wedging and/or binding the two threads when the fastener is rotated in assembly.

In another aspect of the present invention, the guide thread may have a constant profile in each axial section of the helix, and the profile may be a substantially non-apexed broad curve or a series of flat lines and/or curves approximating a smooth curve having a specified radius, with the peak profile being substantially constant throughout the length of the guide thread, so that in the event of undesired contact with a groove present in the peak of the internal thread of the female fastening component, the external thread peak of the male fastening component may neither readily enter any such groove nor present an increasingly pointed or inconsistent peak to the internal thread groove as it rotates while in contact with the internal thread groove. Thus configured, the guide thread of the male fastening component may not be threaded into and embedded in any groove present in the peak of the guide thread of the receiving helix, thereby avoiding misthreading or otherwise interfering with the necessary axial realignment due to cross-threading movement of adjacent cross-threading prevention thread sections of the helix.

In another aspect of an embodiment of the present invention, the peak of the external lead thread of the male fastener component forms a substantially non-helical annular ring within the envelope of the helical path of the standard thread profile around the fastener body. Thus, when presented to the helical peak of the internal lead thread of the female fastener component, the peak of the external lead thread of the male fastener component extends across the groove in the peak of the internal lead thread. When the fastener components are rotated relative to each other, the peak of the external lead thread of the male fastener component passes over the groove in the peak of the internal lead thread of the female fastener component and does not screw into the groove.

Embodiments of the present invention can prevent mis-threading when an externally threaded component engages an internally threaded component. Embodiments of the present invention can prevent cross-threading when an externally threaded component engages an internally threaded component. Embodiments of the present invention can correct linear misalignment (non-collinearity) between two screwably attachable components having mating helical threads. Embodiments of the present invention can correct angular misalignment (angular non-collinearity) between two screwably attachable components having mating helical threads. Embodiments of the present invention correct angular misalignment between the first and second components by causing one or more threads of the first fastening component to act as a cam on the threads of the second fastening component, thereby bringing the first and second components into angular collinear alignment.

Embodiments of the present invention correct for linear misalignment between male and female fastening components by providing an external guide thread of the male fastening component that bridges any grooves present in the peaks of the internal threads of the female fastening component as it slides along the peaks and traverses the edges of the grooves of the female fastening component in bringing the male and female fastening components into co-linear alignment.

Some embodiments of the present invention minimize unintentional contact between a leading thread segment of an external thread helix and a peak of an internal thread helix during camming of a cross-thread-proof thread within a fastener. The leading thread can have a consistent leading thread profile across various cross-sections of the leading thread. The leading thread can have a constant maximum growth rate from its termination point at the fastener shank to the point where the leading thread merges into the next thread form, whether the next thread form is a cross-thread-proof thread, a standard thread, or any other known thread form.

Some embodiments of the present invention have a protruding diameter feature (eg, a guide point or stop point) at the leading end of the male fastening component that limits the angle of misalignment between the male and female components.

A consideration in fastener design is to maintain the length of the fastener's design envelope while adding cross-threading and incorrect threading features to the fastener. Embodiments of the present invention include pilot threads, cross-threading-proof threads, and a stop point to reduce incorrect threading without exceeding the design envelope of the fastener's overall length.

In one aspect of the present invention, the leading thread of a male fastening component can be prevented from being misthreaded into the internal thread helix of a female fastening component by maintaining its external leading thread peak (center) as close as possible to the root of the thread of the adjacent leading thread. Thus, the leading thread forms a substantially non-helical thread within the envelope of the normal external thread helix, thereby allowing the leading thread to intentionally traverse any helical groove in the peak of the internal thread without engaging or misthreading into the groove.

Aspects of the present invention can prevent a leading thread segment of a helix from interfering during thread camming of an adjacent anti-crossthread thread segment of the helix. Interference can be avoided in situations where the leading thread has a substantially constant rate of growth and the leading thread has a thread profile that blends smoothly into the profile of the adjacent anti-crossthread thread, such that the leading thread supports any further camming that may be required to help the anti-crossthread thread achieve its normal function of aligning fastener components.

Certain embodiments of the present invention can eliminate interference of the leading threads of a male fastening component with the peaks of the internal threads of a female fastening component during the camming action of the cross-threading prevention thread. Interference can be eliminated by a consistent, fully formed wide curved leading thread profile that consistently changes in height, width, and profile over the length of the leading thread.

Depending on the length of the guide threads on the male fastener component, the guide threads may intentionally exhibit a consistent maximum thread height at their likely contact points with the peaks of the internal threads to prevent undesirable contact of the guide threads with the peaks of the internal thread helix when the male fastener component is inserted into the female fastener component.

FIG10E shows a side view of a threaded fastener having a guide thread for preventing cross-threading according to the present invention. The guide end 14 of the male fastening component 10 is clearly visible in this view. The outer periphery of the guide end 14 is defined by a standard root diameter 20. From the helix termination point 19, the guide thread 17 grows in height as it wraps around the fastener one and one-fifth of a turn in a clockwise direction until the guide thread merges into the anti-cross-thread thread 16 at a fusion point 18. The guide thread crest 21 grows in height at a constant rate. The anti-cross-thread thread crest 21 is generally constant in height until the anti-cross-thread thread crest grows to merge into the fastening thread 15 at a fusion point 28. The fastening thread crest 23 has a maximum height.

FIG10A illustrates a cross-sectional view of the threads taken at A-A in FIG10E. In FIG10A, two turns of the guide thread 17 are shown adjacent to one turn of the anti-cross-threading thread 16. The lower turn of the guide thread 17, shown on the left side of FIG10A, is approximately 1/6 of the full height of the guide thread. The higher turn of the guide thread 17, shown in the middle of FIG10A, is the full height of the guide thread because the higher turn is located at the fusion point 18 with the anti-cross-threading thread 16, where both the full height of the guide thread 17 and the height of the anti-cross-threading thread 16 are slightly lower than the pitch diameter 24 of the fastening thread 15 (not shown in FIG10A). For illustrative purposes, the fastening thread profile 25 is shown by a dotted line superimposed above the higher turn of the guide thread 17 so that the relative size and profile can be apparent.

In this embodiment, the guide thread 17 has a broadly curved profile as it progresses around the thread helix 11. The guide thread 17 maintains a substantially constant radially curved surface from root to root through its crest 17c. The crest 17c of the guide thread's profile in any axial section is the highest point on a curve having substantially the same radius R throughout this section. The radius R of the curve defining the guide thread profile is determined by extending the curve from each root at a point that would be substantially tangent to the imaginary flanks of a standard thread profile superimposed on the guide thread profile. This is accomplished with the guide thread 17 at its highest point (i.e., at the fusion point 18), with the height of the guide thread 17 just below the pitch line 24 of the fastener. As the height of the thread profile decreases as it extends from the fusion point 18 to the helix termination point 19, the radius R remains substantially constant throughout the length of the guide thread 17, so that the guide thread 17 has the same curvature of its profile in all sections. As such, the width of the leading thread 17 is at its maximum at the fusion point 18 and decreases as the height of the leading thread decreases until the width of the leading thread is zero at the helix termination point 19 .

10A-10E also maintains its proximity to the root it shares with the anti-cross-threading threads 16. As the leading threads 17 become smaller as they wrap around the fastener from the fusion point 18, they remain substantially anchored to the root of the adjacent anti-cross-threading threads 16 of the helix 11.

FIG10A illustrates a cross-sectional view of the threads taken at A-A in FIG10E. At the fusion point 18, the centerline extending vertically through the radially curved guide thread 17 lies on the vertical centerline of the fastening thread profile 25, which is also the centerline of the cross-thread prevention thread 16 at the fusion point 18. As the guide thread 17 winds around the fastener toward the helix termination point 19, the vertical centerline of the guide thread profile deviates from the vertical centerline of the fastening thread profile 25 and gradually approaches the thread root of the adjacent cross-thread prevention thread 16 within one full turn of the guide thread helix and approaches the thread root shared by the guide thread with itself within another one-fifth of the guide thread helix. At the helix termination point 19, the centerline of the guide thread 17 approximately intersects the centerline of the adjacent thread root. At the helix termination point 19, the profile of the guide thread 17 is reduced so that its height and width have essentially reached zero, while its axial position on the male fastening component 10 has approximately reached the root of the adjacent winding of the guide thread 17. This has the effect of anchoring the root 17b of the guide thread 17 to the root of the adjacent thread, while the opposite root 17a of the guide thread 17 moves away from the opposite root of the fastening thread profile 25 and gradually approaches the root of the adjacent anti-cross-threading thread 16. In this way, the guide thread crest 17c forms a substantially annular ring around the male fastening component 10 within the envelope of the helical path of the fastening thread profile 25.

FIG10D illustrates a cross-sectional view of the threads taken at D-D in FIG10E . At this location around the male fastening component 10, the guide thread 17 is adjacent to the anti-cross-thread thread 16, such that the guide thread root 17b is shared with the root of the anti-cross-thread thread 16. The fastening thread profile 25 and the anti-cross-thread thread profile 26 are shown in phantom and superimposed above the guide thread 17 so that their relative sizes and profiles are readily apparent. At this location, the guide thread 17 is approximately 79% of its maximum height. The radius R of the curve defining the profile of the guide thread 17 from the root 17a through the guide thread crest 17c to the other root 17b is the same as the radius of the curved guide thread profile at the fusion point shown in FIG10A . The guide thread root 17b continues to be shared with the root of the anti-cross-thread thread 16, while the opposing guide thread root 17a has been displaced from a position similar to that of a standard thread root (as indicated by the superimposed fastening thread profile 25).

FIG10C illustrates a cross-sectional view of the threads taken at C-C in FIG10E. At this location around the male fastening component 10, the guide thread 17 is adjacent to the anti-cross-thread thread 16, such that the guide thread root 17b is shared with the root of the anti-cross-thread thread 16. The fastening thread profile 25 and the anti-cross-thread thread profile 26 are shown in phantom and superimposed on the guide thread 17 so that their relative sizes and profiles are apparent. At this location, the guide thread 17 is approximately 58% of its maximum height. The radius R of the curve defining the profile of the guide thread 17 from the root 17a through the guide thread crest 17c to the other root 17b is the same as the radius of the curved guide thread profile at the fusion point shown in FIG10A. The leading thread bottom 17b continues to be shared with the bottom of the anti-cross threading thread 16, while the opposing leading thread bottom 17a has been further displaced from a position similar to where the bottom of the standard thread would be (as indicated by the superimposed fastening thread profile 25).

FIG10B illustrates a cross-sectional view of the threads taken at B-B in FIG10E. At this location around the male fastening component 10, the guide thread 17 is adjacent to the anti-cross-thread thread 16, such that the guide thread root 17b is shared with the root of the anti-cross-thread thread 16. The fastening thread profile 25 and the anti-cross-thread thread profile 26 are shown in phantom and superimposed on the guide thread 17 so that their relative sizes and profiles are apparent. At this location, the guide thread 17 is approximately 37% of its maximum height. The radius R of the curve defining the profile of the guide thread 17 from the root 17a through the guide thread crest 17c to the other root 17b is the same as the radius of the curved guide thread profile at the fusion point shown in FIG10A. The leading thread bottom 17b continues to be shared with the bottom of the anti-cross threading thread 16, while the opposing leading thread bottom 17a has been further displaced from a position similar to where the bottom of the standard thread would be (as indicated by the superimposed fastening thread profile 25).

Referring again to FIG. 10A , the lower portion of guide thread 17 is visible on the left side of the figure. Because guide thread 17 extends for one and one-fifth of a helix turn, two turns of guide thread 17 are visible in FIG. 10A : the full-height turn of guide thread 17 is located in the middle of the figure; and the nearly-terminated turn of guide thread 17 is located on the left side of the figure. The root 17b of the nearly-terminated turn is shared with the root 17a of the full-height turn of guide thread 17. Even at this extremely low height, the nearly-terminated turn of guide thread 17 still has a curved profile with the same radius R as the curved profile at other locations.

The embodiment of the present invention illustrated in Figures 10A to 10E has a guide thread 17 that combines a curved profile, a constant maximum rate of change in peak height, and a non-helical winding around the fastener shank. These combined features allow the guide thread 17 to slide along and over the guide threads of an internally threaded female component (not shown) without engaging any depressions and/or grooves in the peaks of the internal female guide threads. The guide thread 17 of the male fastening component 10 thereby allows the adjacent anti-cross-threading threads 16 to more effectively correct any angular or axial misalignment with the internally threaded female component (not shown), so that cross-threading and/or incorrect threading can be avoided.

Figures 11A to 11E illustrate another embodiment of a male fastening component having a guide thread. Figure 11E is a view of the guide end 14, and Figures 11A to 11D are cross-sectional views taken in the axial direction at the position indicated in Figure 11E. This male fastening component 10 has several turns of the fastening thread 15 and more than two and a quarter turns of the guide thread 17. As shown in Figure 11E, the guide thread 17 begins at a helix termination point 19 where the height of the guide thread is zero and grows in height as the guide thread winds around the shank until it reaches its full height at a fusion point 18 where the guide thread merges into the fastening thread 15.

FIG11A illustrates a cross-sectional view of the thread taken at A-A in FIG11E . Referring to FIG11A , the lower portion of the guide thread 17 is visible on the left side of the figure. Because the guide thread 17 extends for two and a quarter turns of the helix, three turns of the guide thread 17 are visible in FIG11A : a lower turn on the left, a medium turn in the middle, and a higher turn on the right. As the guide thread 17 winds around the fastener from the helix termination point 19, it becomes taller and remains anchored to the root it shares with its own medium-sized turn for a full turn of the guide thread helix. At the helix termination point 19, the guide thread 17 approximately intersects the centerline of the adjacent root. At the helix termination point 19, the thread profile of the guide thread 17 is reduced so that the height and width of the guide thread are essentially zero, and the guide thread is located axially on the male fastening component 10 approximately at the root of the adjacent turn of the guide thread 17. This has the effect of anchoring the root 17b of the guide thread 17 to the root of the adjacent winding, while the opposite root 17a of the guide thread 17 has left the opposite root of the fastening thread profile 25 (shown by the dotted line) and gradually approaches the anchored root 17b. In this way, the guide thread crest 17c forms a substantially annular ring around the male fastening component 10 within the envelope of the helical path of the fastening thread profile 25. At cross section A-A, the lowest guide thread winding is about 8.3% of the full height, the middle guide thread winding is about 52.7% of the full height, and the highest guide thread winding is about 97.2% of the full height.

FIG11B illustrates a cross-sectional view of the threads taken at B-B in FIG11E . At this location around the male fastening component 10, the lower winding of the guide thread 17 is adjacent to the upper winding of the guide thread 17, such that the lower guide thread root 17b is shared with the upper guide thread root 17a. The fastening thread profile 25 is shown in phantom and superimposed above the windings of the guide thread 17 so that the relative sizes and profiles are apparent. At cross-section B-B, the lower guide thread winding is approximately 19.4% of the full height, and the upper guide thread winding is approximately 63.9% of the full height. The radius R of the curve defining the profile of the guide thread 17 from the root 17a through the guide thread crest 17c to the lower winding of the other root 17b is the same as the radius of the arc that would extend from the root to the root of the fastening thread profile 25 (similar to the anti-cross-thread thread profile 26). The lower winding leading thread bottom 17b continues to be shared with the higher winding bottom 17a of the leading thread 17, while the opposing leading thread bottom 17a is displaced from a position similar to where the standard thread bottom would be (as indicated by the superimposed fastening thread profile 25).

FIG11C illustrates a cross-sectional view of the threads taken at C-C in FIG11E . At this location around the male fastening component 10, the lower winding of the guide thread 17 is adjacent to the upper winding, such that the guide thread root 17b of the lower winding of the guide thread 17 is shared with the root 17a of the upper winding. The fastening thread profile 25 is shown in phantom and superimposed above the windings of the guide thread 17 so that the relative size and profile can be readily apparent. At cross-section C-C, the lower guide thread winding is approximately 30.5% of the full height and the upper guide thread winding is approximately 75.0% of the full height. The guide thread profile may include a curved surface having the same radius R as the radius of the arc extending from the root to the root of the fastening thread profile 25 (similar to the anti-cross-thread thread profile 26).

FIG11D illustrates a cross-sectional view of the threads taken at D-D in FIG11E . At this location around the male fastening component 10, the lower winding of the guide thread 17 is adjacent to the upper winding, such that the guide thread root 17b of the lower winding of the guide thread 17 is shared with the root 17a of the upper winding. The fastening thread profile 25 is shown in phantom and superimposed above the windings of the guide thread 17 so that the relative size and profile are apparent. At cross-section D-D, the lower guide thread winding is approximately 41.7% of the full height, and the upper guide thread winding is approximately 86.1% of the full height. The guide thread profile of the upper winding can include a combination of curved and straight surfaces, depending on the configuration of the rolling die used to produce the guide threads. Specifically, the guide thread profile of the upper winding can include a combination between a cross-threading-proof thread and a standard thread, as shown in FIG11D . The lower turns of the leading thread may have a curve having the same radius as the radius of the arc that would extend from the root 17a to the root 17b (similar to the anti-cross-thread thread profile 26).

Figures 12A to 12E illustrate another embodiment of a male fastening component having a guide thread. Figure 12E is a view of the guide end 14, and Figures 12A to 12D are cross-sectional views taken in the axial direction at the position indicated in Figure 12E. This male fastening component 10 has a guide thread 17, a cross-threading prevention thread 16, and several windings of a fastening thread 15. As shown in Figure 12E, the guide thread 17 begins at a helix termination point 19 where the guide thread has zero height and grows in height as it winds around the shank until it reaches its full height at a fusion point 18 where the guide thread merges into the cross-threading prevention thread 16.

FIG12A illustrates a cross-sectional view of the threads taken at A-A in FIG12E . Referring to FIG12A , the lower portion of the guide thread 17 is visible on the left side of the figure. Because the guide thread 17 extends over more than one turn of the helix, two turns of the guide thread 17 and one turn of the cross-threading prevention thread 16 are visible in FIG12A : the lower turn of the guide thread 17 on the left, the middle, higher turn of the guide thread 17, and the cross-threading prevention thread turn on the right. As the guide thread 17 winds around the fastener from the helix termination point 19, the guide thread becomes taller, but in this embodiment, the guide thread does not remain anchored to the roots of its adjacent turns. At the helix termination point 19, the guide thread 17 is approximately located in the middle of the fastening thread profile 25 (shown in phantom and superimposed above the guide thread 17). At the helix termination point 19, the thread profile of the guide thread 17 is reduced so that its height and width are essentially zero, while the guide thread axially located on the male fastening component is separated and spaced apart from the roots of the adjacent windings of the guide thread 17. At cross-section A-A, the lower guide thread winding is approximately 16.7% of the full height, the upper guide thread winding is approximately 100% of the full height of the guide thread 17, and the cross-threading prevention thread 16 is at its full height. As shown in Figures 12A and 12E, the guide thread 17 is at its full height at the fusion point 18 where it merges into the cross-threading prevention thread 16. As shown in Figure 12E, the cross-threading prevention thread 16 merges into the fastening thread 15 at a second fusion point 28.

FIG12B illustrates a cross-sectional view of the threads taken at B-B in FIG12E. At this location around the male fastening component 10, the guide thread 17 does not share a root with the adjacent anti-cross-threading thread 16 because there is a space separating the guide thread from the adjacent anti-cross-threading thread. The fastening thread profile 25 is shown in phantom and superimposed above the turns of the guide thread 17 so that the relative size and profile can be readily apparent. At cross-section B-B, the guide thread is approximately 37.5% of its full height. The radius R of the curve defining the profile of the guide thread 17 from the root 17a through the guide thread crest 17c to the other root 17b is the same as the radius of the arc that would extend from the root to the root of the fastening thread profile 25 (similar to the anti-cross-threading thread profile 26).

FIG12C illustrates a cross-sectional view of the threads taken at C-C in FIG12E. At this location around the male fastening component 10, the guide thread 17 still does not share a root with the adjacent anti-cross-thread thread 16. The fastening thread profile 25 is shown in phantom and superimposed over the turns of the guide thread 17 so that the relative size and profile can be readily apparent. At cross-section C-C, the guide thread is approximately 58.3% of the full height of the guide thread 17. The guide thread profile may include a curved surface having the same radius R as the arc extending from the root to the root of the fastening thread profile 25 (similar to the anti-cross-thread thread profile 26).

FIG12D illustrates a cross-sectional view of the threads taken at D-D in FIG12E. At this location around the male fastening component 10, the guide thread 17 is still spaced apart from the adjacent anti-cross-threading thread 16. The fastening thread profile 25 is shown in phantom and superimposed above the guide thread 17 so that the relative size and profile can be readily apparent. At cross-section D-D, the lower guide thread is approximately 79.2% of the full height. The guide thread profile may have a curve having the same radius as the arc extending from root 17a to root 17b (similar to the anti-cross-threading thread profile 26).

Figures 13A through 13E illustrate another embodiment of a male fastening component having a guide thread. Figure 13A illustrates a cross-sectional view of the thread taken at A-A in Figure 13E. Referring to Figure 13A, the lower portion of the guide thread 17 is visible on the far left of the figure. Because the guide thread 17 extends for more than two and a quarter turns of the helix, three turns of the guide thread 17 are visible in Figure 13A: a lower turn on the far left, a medium turn in the middle, and a higher turn on the right. As the guide thread 17 winds around the fastener from the helix termination point 19, the guide thread becomes taller and maintains its medium-sized turns as far away as possible within a full turn of the guide thread helix, while the small turns remain within the fastening thread profile 25 (shown in dashed lines superimposed above the guide thread). Figure 13B illustrates a cross-sectional view of the thread taken at B-B in Figure 13E. At this position around the male fastening component 10, the lower winding of the leading thread 17 is as far away as possible from the adjacent higher winding of the leading thread 17. FIG13C illustrates a cross-sectional view of the threads taken at C-C in FIG13E. At this position around the male fastening component 10, the lower winding of the leading thread 17 is still as far away as possible from the adjacent higher winding of the leading thread 17, while remaining within the fastening thread profile 25 (shown in dashed lines superimposed above the leading thread). FIG13D illustrates a cross-sectional view of the threads taken at D-D in FIG13E. At this position around the male fastening component 10, the lower winding of the leading thread 17 does not yet share a root with the adjacent higher winding.

In some embodiments of the present invention, the thread profile of the guide thread may be a curve at its peak over the entire length of the guide thread (approximately one and one-fifth turns of the helix), wherein the curve has the same radius at each axial segment, so that the thread profile of the guide thread in any segment effectively bridges any groove present in the internal guide thread of the female fastener component.

While alternative embodiments of the guide thread do not have a height that increases at a constant rate as the guide thread winds around the shank of the fastener, one aspect of the inventive guide thread is that the guide thread does not have a localized bump, point, or abrupt increase in guide thread height or profile that can be embedded in a groove in the peak end of the internal guide thread of the female fastening component and continue to be screwed into the groove. Some embodiments of the present invention have guide threads that have a constant growth rate associated with a uniform thread profile, which prevents the guide thread from entering any groove present in the internal guide thread of the female fastening component. Embodiments of the present invention have a guide thread profile that further allows the guide thread to slide over any groove present in the internal guide thread of the female fastening component with minimal applied axial force. As a result, the male fastening component may not be screwed into and/or stuck on any peak end groove of the female fastening component.

14A to 14F show cross-sectional and end views of a female fastening component having internal guide threads and a corresponding male fastening component inserted into the female fastening component without any relative rotation of the components. The female fastening component 30 having internal guide threads 31 is the same as that illustrated in FIG4A to 4F. As shown in FIG14A to 14E (which are cross-sectional views of the threads at the positions identified in FIG14F), the male fastening component 10 can be inserted into the female fastening component without rotational movement. Before the components are rotated relative to each other to engage the threads, the guide threads 17 of the male fastening component 10 bridge the different depths of the grooves 32 in the peaks of the internal guide threads 31 of the female fastening component 30 without entering the grooves in any section of the grooves 32.

Figures 15A through 15C show side views of a male fastening component of the present invention having a leading thread and various lead-in points. The helix of thread 11 wound around shank 12 of male fastening component 10 can adopt several significantly different profiles over the length of the helix as the helix progresses from the head (not shown) around shank 12 to leading end 14 of the fastener. Male fastening component 10 can have several turns of fastening thread 15, where fastening thread 15 can be a standard thread (see Figure 1) or any other thread known to those skilled in the art. As helix 11 winds toward leading end 14, fastening thread 15 can be followed by a low section of anti-cross-threading thread 16, where fastening thread 15 merges into anti-cross-threading thread 16 on the same helix 11. Anti-cross-threading thread 16 has a profile that imparts anti-cross-threading functionality to that section of the helix because at least a portion of one turn of the thread helix has a transitional curved surface from a smaller diameter to a larger diameter. A detailed description of the cross-threading prevention threads 16 is provided in U.S. Patent No. 5,730,566, which is incorporated herein by reference in its entirety. The cross-threading prevention threads 16 may be followed by a guide thread 17 on the helical line 11, as described in detail with reference to Figures 10A through 10E. These thread profiles, regardless of their specific localized shape and profile, may be contained within the envelope defined by the profile of the fastening threads 15. At the leading end 14, a lead-in point 50 is formed on the male fastening component 10. A detailed description of the lead-in point 50 is provided in U.S. Patent No. 6,062,786, which is incorporated herein by reference in its entirety. In Figure 15A, the lead-in point 50 tapers from a larger diameter at the leading thread 17 to a smaller diameter at the tip. In Figure 15B, the lead-in point 50 is cylindrical in shape with a diameter slightly larger than the minimum diameter of the fastening threads 15. In Figure 15C, the lead-in point 50 is cylindrical in shape with a diameter slightly smaller than the minimum diameter of the fastening threads 15. In other embodiments, any lead-in point known to those skilled in the art may be formed on the leading end of the male fastening component. Still other embodiments may include a lead-in point that is larger in diameter than the minimum diameter at the root of the lead and/or fastening threads. With the addition of a larger diameter lead-in point to the male fastening component, the lead thread may be relatively low, with the rate of change in height of the lead thread being the same. The relatively low lead thread may be the result of the lead thread terminating on a higher surface (i.e., the larger diameter lead-in point).

The minimum diameter of the guide thread 17 can be smaller or larger than the minimum diameter of the anti-cross-threading thread 16 or the fastening thread 15. For example, as shown in FIG. 15 , the lead-in point 50 can have an outer diameter larger than the minimum diameter of the fastening thread 15. The minimum diameter of the guide thread 17 can be largest at the helix termination point 19 and can decrease as the guide thread winds around the shank to the fusion point 18. The minimum diameter of the guide thread 17 can decrease with each turn from the guide thread 17 through the anti-cross-threading thread 16 until the minimum diameter reaches the minimum diameter of the fastening thread 15. In similar embodiments, the minimum diameter can decrease, but the fastener does not have a lead-in point. In alternative embodiments, with or without a lead-in point, the minimum diameter can increase as the guide thread 17 winds from the helix termination point 19 toward the fusion point 18 and can increase again after passing the fusion point 18. In alternative embodiments, the minimum diameter gradually decreases or increases from the guide thread 17 to the next thread, but can remain constant for the entire turn of the guide thread 17.

FIG16A-16B illustrate cross-sectional side views of different guide threads 17 and cross-threading prevention threads 16 on different male fastener components of the present invention, wherein the different fasteners have different minimum diameters around the guide threads 17. These configurations illustrate that it is possible to vary the diameter at the root of the guide threads without changing the guide threads' functionality to prevent misthreading. In FIG16A , the fastener 10 has a cylindrical lead-in point 43 that is larger in diameter than the minimum diameter of the cross-threading prevention threads 16 and extends only to the guide threads 17, such that the guide thread flanks 17b are present on the right side of the guide threads 17 and are absent on the other side. In FIG16B , the fastener 10 has a cylindrical lead-in point 43 that is larger in diameter than the minimum diameter of the cross-threading prevention threads 16 and extends all the way to the cross-threading prevention threads 16, such that no guide threads 17 protrude upward through the lead-in point 43. This illustration illustrates how the leading thread 17 can taper from one and a half turns down to about one turn, with a portion of the leading thread being covered by a relatively larger diameter lead-in point 43. In FIG16C , the fastener 10 has a cylindrical lead-in point 44 that is smaller in diameter than the minimum diameter of the anti-cross threading threads 16 and extends only to the leading thread 17, such that the leading thread flank 17e is larger than the leading thread flank 17b. In FIG16D , the fastener 10 has a cylindrical lead-in point 44 that is smaller in diameter than the minimum diameter of the anti-cross threading threads 16 and extends to the anti-cross threading threads 16, such that the leading thread flanks 17e and 17f are the same size or nearly the same size.

The present invention, therefore, is well adapted to carry out the objects and obtain the ends and advantages mentioned as well as others inherent therein. While presently preferred embodiments of the invention have been shown for purposes of disclosure, numerous changes in the details or procedures for achieving the desired results will readily suggest themselves to one skilled in the art, and such changes are encompassed within the spirit of the invention and the scope of the appended claims.

Claims (12)

1. A convex anti-mis-tightening fastening component, comprising: The handle has a guide end and a tool engagement end; A head, which is formed at the tool engagement end of the handle; At least one convex fastening thread is formed on the outside of the shank as a plurality of threaded turns adapted to mate with a corresponding concave fastening thread formed inside the concave fastening member; At least one convex guide thread is formed at the guide end on the exterior of the shank, the at least one convex guide thread being at least half a turn around the shank and including a curved tooth profile defined by an arc having a radius approximately equal to the radius of the arc tangent to two tooth flanks of the thread profile of the at least one convex fastening thread and located below the pitch diameter of the at least one convex fastener thread. In the case of the incorrect tightening, the convex fastener and the concave fastener are substantially misaligned relative to each other along their helical axis. 2. The convex anti-mis-tightening fastening component according to claim 1, wherein the convex guide thread is at least three-quarters of a turn around the shank. 3. The convex anti-mis-tightening fastening component according to claim 1, wherein the convex guide thread is a turn of at least one and a fifth around the handle. 4. The convex anti-mis-tightening fastening component according to claim 1, wherein the thread profile at each cross-section between the ends of the convex guide thread is defined by an arc having approximately the same radius. 5. The convex anti-mis-tightening fastening component according to claim 1, wherein at least one convex guide thread is lowest at the beginning of the convex guide thread loop and highest at the other end of the convex guide thread loop, wherein the convex guide thread includes a crest having a height that changes at a substantially constant rate between the beginning and the other end of the convex guide thread loop. 6. The convex anti-mis-tightening fastening component according to claim 1, wherein the convex guide thread includes a convex guide thread flank, the convex guide thread flank being anchored to the root of an adjacent threaded loop along the entire length of the convex guide thread. 7. The convex anti-mis-tightening fastening component according to claim 1, wherein the convex guide thread includes a tooth profile having a height and shape adapted to prevent mis-tightening into a groove in the crest of the concave guide thread in the interior of the concave fastening component. 8. The convex anti-mis-tightening fastening component according to claim 1, wherein the continuous thread helix includes the at least one convex guide thread and the at least one convex fastening thread. 9. The convex anti-mis-tightening fastening component according to claim 1, further comprising at least one convex anti-mis-tightening thread, the at least one convex anti-mis-tightening thread acting as a cam on a concave fastening thread inside the concave fastening component when the convex fastening component and the concave fastening component rotate relative to each other, thereby making the longitudinal axis of the handle and the longitudinal axis of the concave fastening component substantially collinearly aligned. 10. The convex anti-mis-tightening fastening component according to claim 1, further comprising at least one convex anti-mis-tightening thread, the at least one convex anti-mis-tightening thread having an outer diameter smaller than the large diameter of the at least one convex fastening thread, and wherein the at least one convex anti-mis-tightening thread includes an outer surface, the outer surface being a curved shape approximating a plurality of flat and curved surfaces and having a tooth profile that engages within the tooth profile of the at least one convex fastening thread. 11. The convex anti-mis-tightening fastening component according to claim 1, further comprising at least one anti-mis-tightening thread, the at least one anti-mis-tightening thread aligning the longitudinal axis of the shank with the longitudinal axis of the concave fastening component, wherein the continuous thread helix includes the at least one convex guiding thread, the at least one convex anti-mis-tightening thread and the at least one convex fastening thread. 12. The convex anti-mis-tightening fastening member according to claim 1, further comprising an inlet point formed at the guide end of the handle.