Thread formation and thread locking fasteners

Abstract

A fastener that combines thread-forming and thread-locking is disclosed. The fastener includes three sections. A first thread section utilizes a first thread-forming thread form having an increasing outer diameter. A second thread section extends from the end of the first section utilizing the first thread-forming thread form and continues at a constant diameter. A third thread section utilizes a thread-locking thread form that continues substantially along the remainder of the fastener shaft.

Description

Technical Field

[0001] The present invention relates to a threaded fastener.

Background Art

[0002] Background Information Conventional threaded fasteners (e.g., screws or bolts) can be designed to have a self-tapping thread forming action. An example of such a self-tapping fastener is described in U.S. Patent No. 9,404,524 to Alan Pritchard, titled "High Performance Thread Rolling Screw / Bolt For Use in An Unthreaded Nut Anchor", the content of which is incorporated herein by reference.

[0003] Other conventional fasteners can include a thread locking mechanism that can be achieved, for example, by mechanical interference between the fastener and a nut member. An exemplary thread locking fastener is described in U.S. Patent No. 7,722,304 to Alan Pritchard, titled "Fastener and Fastener Assembly", the content of which is incorporated herein by reference.

[0004] A significant drawback of conventional fasteners is that they are optimized for either thread forming or thread locking, but not both. As a result, the user has to make a decision as to which feature is more important for a particular application, which may lead to a sub-optimal use of such fasteners.

[0005] Summary The disadvantages of the prior art are overcome by providing an exemplary fastener optimized for both thread formation and thread locking. The fastener includes two distinct thread profiles divided into three zones along the shaft of the fastener. A first zone utilizing the thread profile for thread formation is in the immediate vicinity of the entry point of the fastener. Along the first zone, the outer diameter of the thread profile increases along a first (e.g., 2 - 5) pitch. A second zone transitions from the first zone and utilizes the same thread profile for thread formation but maintains a constant thread outer diameter. The second zone extends beyond the first zone, e.g., over 2 - 3 pitches. A third zone utilizing the thread profile for thread locking also maintains a constant outer diameter.

[0006] According to an exemplary embodiment of the present invention, the first and second thread profiles can be selected to complement each other to achieve a desired level of mechanical interference (i.e., thread locking). Further, by utilizing the present invention, the second thread profile (for thread locking) can be optimized to cooperate with the threads created by the first thread profile (for thread formation). This can result in an optimized thread locking mechanism.

[0007] The above and further advantages of embodiments of the present invention can be understood in relation to the accompanying drawings, in which like reference numerals indicate the same or functionally similar elements.

Brief Description of the Drawings

[0008]

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[0009] Detailed description of exemplary embodiments Figure 1A is a cross-sectional view of an exemplary thread-forming and thread-locking fastener 100 according to an exemplary embodiment of the present invention. The fastener 100 includes an entry point 105 and a head 110, with a shaft 115 extending therebetween. By way of example, the entry point 105 is shown as having a substantially flat end. However, it should be noted that in alternative embodiments of the present invention, the fastener 100 may have an entry point 105 that is rounded, pointed, etc. Therefore, the description of the entry point 105 being substantially flat should be construed as merely illustrative. The head 110 is illustratively shown as having a hexagonal shape for use with a driving device for insertion. The head 110 extends over a certain length 120 on the same axis of the shaft 115 to enable a driver (such as a wrench) to engage the head 110 so as to apply torque to the fastener for insertion into a nut member (not shown). The head 110 includes a substantially flat bottom 125 designed to abut in the same plane as a nut member (not shown) when the fastener is fully inserted. As will be understood by those skilled in the art, the head 110 can have a plurality of different shapes based on the desired driving device. Accordingly, the description of the head 110 having a hexagonal shape should be construed as merely illustrative.

[0010] The body or shaft 115 of the fastener 100 includes a plurality of threaded regions, for example, a first region 130, a second region 135, and a third region 140. As an example, the three regions are utilized to perform both a threading function and a thread locking function once the fastener is inserted into the nut member. The first region 130 is an exemplary first thread shape that angles outward from the core (center) while increasing in diameter as the region moves away from the entry point 105 of the fastener, and is, for example, about 2 to 5 pitches in length. That is, the outer diameter of the first region 130 is smallest at the entry point 105 and increases as the thread moves along the shaft 115 toward the head 110. The second region 135 includes, as an example, an additional 1 to 3 pitches that are of the first (thread-forming) thread shape but have a substantially constant outer diameter. As shown in FIG. 1A, the first thread shape includes, as an example, a cross-section of a thread shape formed at a substantially 60° angle. In an exemplary embodiment, the first thread shape can include that described in U.S. Patent No. 9,404,524 incorporated above. It should be noted that while a specific thread-forming thread shape is illustrated and described, the principles of the present invention can utilize any thread-forming thread shape in alternative embodiments of the present invention. Accordingly, the specific thread-forming thread shape illustrated and described herein should be construed as merely exemplary.

[0011] The third region 140 utilizes a second thread shape that is, as an example, a thread shape for thread locking. As shown in FIG. 1A, the exemplary second thread shape includes a thread formed at a 60° angle at the root (base, bottom) of the thread that transitions to a thread formed at a 30° angle at the tip. The exemplary thread locking thread shape is described in U.S. Patent No. 7,722,304 incorporated above. It should be noted that while a specific thread locking shape is illustrated and described, the principles of the present invention can utilize any thread locking thread shape in alternative embodiments of the present invention. Accordingly, the specific thread locking thread shape illustrated and described herein should be construed as merely exemplary.

[0012] Thus, during operation, when the fastener 100 according to an exemplary embodiment of the present invention is inserted into the nut member, when the fastener is first inserted, the threads in the first region engage the nut member. The threads in the first and second regions deform the nut member to create threads. Continuing to insert the fastener into the nut member, the threads in the third region engage the newly created threads, causing mechanical interference, thereby creating a locking mechanism. As an example, the second thread shape is selected to complement the first thread shape. According to an alternative embodiment of the present invention, the two thread shapes can be selected such that the thread locking shape (the second thread shape) is designed with deductive knowledge of the dimensions of the threads created in the nut member by the thread forming shape (the first thread shape). When the fastener creates an internal thread in an unthreaded nut member, the threads of the thread locking shape can be configured for optimized performance with the internal thread. Examples of deformations are described below in connection with FIGS. 4A, 4B, 4C, 5A, 5B, and 5C.

[0013] Figure 1B is an exemplary illustration of the head 110 of the fastener 100 viewed along the long axis of the fastener, according to an exemplary embodiment of the present invention. As described above, the illustration and description of the exemplary head having a hexagonal shape should be construed as merely exemplary. Figure 1C is a view of the fastener 100 from the inlet point 105 along the long axis of the fastener, according to an exemplary embodiment of the present invention. As can be understood from Figure 1C, the shaft 115 of the fastener is shaped, as an example, to have a plurality (e.g., three) of lobes in cross-section. It should be noted that the use of a multi-lobed shaft is merely exemplary, and the principles of the present invention can be utilized with fasteners having a shaft that is substantially circular. As will be understood by those skilled in the art, cross-sections of various types of fastener shafts can be utilized to achieve the desired characteristics of the fastener. More specifically, it is particularly contemplated that, according to an alternative embodiment of the present invention, a shaft having more than three lobes can be utilized. Further, in an alternative embodiment, the shaft can have a varying cross-section. For example, the shaft can have a region of substantially circular cross-section near the inlet point, but can transition to a region of non-circular cross-section along the length of the shaft. An exemplary region of non-circular cross-section is, for example, a region of three-lobe cross-section. However, it is particularly contemplated that, according to an alternative embodiment of the present invention, other shapes in the region of substantially non-circular cross-section can be utilized. The principles of the present invention can be utilized with a wide range of cross-sectional shapes of the fastener shaft 115 to achieve the desired functionality.

[0014] Figure 2 is an enlarged view of the inlet point end of the fastener 100, according to an exemplary embodiment of the present invention. As can be discerned from Figure 2, the first region 130 has an increasing outer diameter as it moves away from the inlet point 105. The first region utilizes, as an example, a first thread shape that is a thread shape for thread formation. The second region 135 continues the use of the thread for thread formation, but is substantially constant in overall diameter, unlike the first region 130 having an increasing overall thread diameter. The third region 140 then utilizes a second thread shape (e.g., the thread shape of a thread lock) for the remainder of the fastener 100.

[0015] FIG. 3 is an exemplary view of a blank (material piece) 300 with a head for use in forming the fastener 100 according to an exemplary embodiment of the present invention. As an example, the blank 300 consists of a single diameter blank that reduces manufacturing difficulty. However, it is specifically contemplated that the principles of the present invention can be utilized with more sophisticated blanks.

[0016] FIGS. 4A, 4B, and 4C show exemplary thread profiles that can be utilized in alternative embodiments of the present invention. It should be noted that each thread profile has the same cross-sectional area. FIG. 4A is a representative example of an exemplary 60° thread profile as shown in FIG. 1. FIG. 4B is a representative example of an exemplary rounded thread profile. FIG. 4C is a representative example of an exemplary triangular thread form having a 60° / 30° thread profile. It should be noted that different thread profiles can be utilized in alternative embodiments of the present invention. Thus, it is specifically contemplated that the thread profiles shown in FIGS. 4A, 4B, and 4C are merely exemplary.

[0017] FIGS. 5A, 5B, and 5C show an exemplary range of potential mechanical interferences that can be achieved by utilizing different thread profiles for the nut member and the fastener according to exemplary design choices in an exemplary embodiment of the present invention. The various figures show combinations of the thread profiles described above in relation to FIGS. 4A, 4B, and 4C. As can be gleaned from FIGS. 5A, 5B, and 5C, different degrees of mechanical interference can be achieved by changing the shape of the female and male threads. In alternative embodiments, a desired amount of mechanical interference can be achieved by selecting various combinations of thread profiles.

[0018] Figure 6 is a cross-sectional view 600 of the insertion of the fastener 100 into the threaded nut member 605 according to an exemplary embodiment of the present invention. The threaded nut member 605 includes, as an example, a set of pre-formed threads 610. Figure 600 shows the fastener 100 and the nut 605 just prior to the insertion of the end 105 of the fastener 100 into the threaded nut member 605. The view along the cutting plane A-A shows an exemplary cross-section 615 of the fastener 100 and the threaded nut member.

[0019] Figure 7 is a cross-sectional view 700 of the insertion of the fastener 100 into the threaded nut member 605 according to an exemplary embodiment of the present invention. In Figure 700, the first region 130 and the second region 135 of the fastener 100 are inserted into the threaded nut member 605. As can be seen in the enlarged view, a space is left between the threads of the first and second regions and the female threads 610 of the threaded nut member 605.

[0020] Figure 8 is a cross-sectional view 800 of the insertion of the fastener 100 into the threaded nut member according to an exemplary embodiment of the present invention. In Figure 800, the threads 130 of the first region pass almost completely through the threaded nut member 605, while the threads 135 of the second region are completely within the nut member 605. As can be seen, the threads 140 of the third region cause tip penetration at the location 805 within the nut member.

[0021] Figure 9 is a cross-sectional view 900 of the insertion of the fastener 100 into the threaded nut member 605 according to an exemplary embodiment of the present invention. In Figure 900, the threads 130 of the first region and the threads 135 of the second region pass completely through the nut member 605, and for each female thread 605, there is a tip penetration location 905 of the threads 140 of the third region. With the fastener 100 inserted as shown in Figure 9, the tip penetration location 905 generates a mechanical locking mechanism, which thereby acts to fix the fastener in the threaded nut member.

[0022] In an exemplary embodiment of the present invention, the thread shape of the thread formation for the threads in the first and second regions is designed to slightly increase the diameter of the threads of the threaded nut member. This size change enables the fastener to be configured such that there is an optimized interference between the sized threads and the threads of the thread lock of the threads in the third region. By selecting the thread shape and size for the threads in the first and second regions, a desired amount of mechanical interference with the threads in the third region can be achieved. However, it should be noted that in an alternative embodiment of the present invention, the pre-formed female thread is not engaged by the threads in the first and second regions. Accordingly, the description of the enlarged female thread should be construed as merely exemplary.

[0023] Figure 10 is a cross-sectional view 1000 of the insertion of the fastener 100 into the unthreaded nut member 1005 according to an exemplary embodiment of the present invention. In Figure 1000, the fastener 100 is about to be inserted into a nut member 1005 having an unthreaded opening or hole 1010.

[0024] Figure 11 is a cross-sectional view 1100 of the insertion of the fastener 100 into the unthreaded nut member 1005 according to an exemplary embodiment of the present invention. Figure 1100 shows the time when the threads in the first and second regions are fully inserted into the unthreaded nut member.

[0025] Figure 12 is a cross-sectional view 1200 of the insertion of the fastener 100 into the unthreaded nut member 1005 according to an exemplary embodiment of the present invention. At this point, the threads 140 in the third region have entered the previously formed threads, resulting in tip penetration at location 1205.

[0026] FIG. 13 is a cross-sectional view 1300 of the insertion of the fastener 100 into the unthreaded nut member according to an exemplary embodiment of the present invention. In FIG. 1300, the threads in the first and second regions pass through the nut member 1005, and the plurality of threads in the third region engage the nut member 1005 at the plurality of tip penetration locations 1305.

[0027] With reference to FIGS. 6-9, as described above, in an exemplary embodiment of the present invention, the threads in the first and second regions can be sized to create threads of an optimal size to achieve a desired mechanical interference with the threads in the third region.

[0028] It should be noted that although the present invention has been described in relation to a specific thread shape, the principles of the present invention can be utilized with various thread shapes of thread formation and / or thread locking. Therefore, the specific descriptions regarding the specific thread shape included herein should be regarded as merely illustrative. Further, various descriptions regarding the number of thread pitches in various regions are given, but as will be understood by those skilled in the art, the number of pitches in various regions may vary depending on the intended application. Therefore, the descriptions regarding the specific number of pitches in various regions should be construed as illustrative.

[0029] This description has been written with respect to various exemplary embodiments of the present invention. As will be understood by those skilled in the art, various modifications can be made to the embodiments described herein without departing from the spirit or scope of the present invention. Therefore, the described embodiments should be construed as merely illustrative.

Claims

**Claim 1** A fastening device comprising a shaft having a cross-sectional shape with three or more lobes and having an entry point at a first end and a head at a second end, wherein the shaft is cut with a first thread profile in a first region and a second region, the first thread profile being a thread-forming thread profile designed to produce a female thread in a nut member, the first region starting from the entry point and extending along the shaft over approximately a first predetermined number of thread pitches, the diameter of the first region increasing from the entry point to the second region, the second region having a constant outer diameter and extending over approximately a second predetermined number of thread pitches, a third region having a second thread profile different from the first thread profile extending from the transition from the second region towards the bottom of the head along a substantial part of the remainder of the shaft, the second thread profile being a thread-locking thread profile, the second thread profile being selected based on the first thread profile such that a desired amount of mechanical interference is created between the female thread formed by the first thread profile and the second thread profile, the fastening device. **Claim 2** A fastening device comprising a shaft having a cross-sectional shape and having an entry point at a first end and a head at a second end, wherein the cross-sectional shape of the shaft transitions from a substantially circular cross-section at the entry point to a substantially non-circular cross-section along the shaft, wherein the shaft is cut with a first thread profile in a first region and a second region, the first thread profile being a thread-forming thread profile designed to produce a female thread in a nut member, the first region starting from the entry point and extending along the shaft over approximately a first predetermined number of thread pitches, the diameter of the first region increasing from the entry point to the second region, the second region having a constant outer diameter and extending over approximately a second predetermined number of thread pitches, A third region has a second thread shape different from the first thread shape and extends from the transition from the second region toward the bottom of the head along a substantial portion of the remaining portion of the shaft. The second thread shape is a thread shape of a thread lock and is selected based on the first thread shape so as to cause a desired amount of mechanical interference between the female thread formed by the first thread shape and the second thread shape. A fastener.

3. A fastener comprising: a shaft having a cross-sectional shape and having an entry point at a first end and a head at a second end, wherein the cross-sectional shape of the shaft transitions from a substantially non-circular cross-section at the entry point to a substantially circular cross-section along the shaft, the shaft being engraved with a first thread shape in a first region and a second region, the first thread shape being a thread-forming thread shape designed to create a female thread in a nut member, the first region starting from the entry point and extending along the shaft over approximately a first predetermined number of thread pitches, the diameter of the first region increasing from the entry point to the second region, the second region having a constant outer diameter and extending over approximately a second predetermined number of thread pitches, A third region has a second thread shape different from the first thread shape and extends from the transition from the second region toward the bottom of the head along a substantial portion of the remaining portion of the shaft. The second thread shape is a thread shape of a thread lock and is selected based on the first thread shape so as to cause a desired amount of mechanical interference between the female thread formed by the first thread shape and the second thread shape. A fastener.

4. The fastener according to any one of claims 1 to 3, wherein the first thread shape has an angle of about 60°.

5. The fastener according to any one of claims 1 to 3, wherein the first thread shape has a substantially rounded side surface.

6. The fastener according to any one of claims 1 to 3, wherein the first thread shape has a substantially parabolic side surface.

7. The fastener according to any one of claims 1 to 6, wherein the first predetermined number of thread pitches is 3.

8. The fastener according to any one of claims 1 to 7, wherein the second predetermined number of thread pitches is 6.

9. The fastening tool according to any one of claims 1 to 8, wherein the first thread shape has a size such that a female thread optimized to engage with the second thread shape is created.

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