A lockbolt which includes a head portion and a shaft which extends from the head portion. The shaft includes at least a portion which is threaded and has a multi-lobular profile. A collar is swageable onto the multi-lobular threaded portion, and thereafter the lobes provide that the collar does not tend to vibrate loose from the threading. The fact that the section which has a multi-lobular profile is also threaded provides that the collar (or a conventional threaded nut) can be selectively rotatably removed and re-installed on the lockbolt. Before swaging, the collar may initially include a cylindrical bore, or a bore which is multi-faceted, preferably generally corresponding to the profile of the multi-lobular portion of the lockbolt. The lockbolt may also include a frangible pintail, wherein the multi-lobular threaded portion is disposed between the head portion of the bolt and the frangible pintail.

BACKGROUND

The present invention generally relates to lockbolts, and more specifically relates to a multi-lobular lockbolt which is configured to be installed vis-a-vis a collar which is swaged onto the bolt.

Some conventional lockbolts include a frangible pintail while others do not. As shown inFIG. 1, a typical lockbolt10which includes a frangible pintail12includes: a head14, a threaded shaft16and a frangible pintail12having annular ribs18, wherein the head14is at one end20of the bolt10, the frangible pintail12is at the other end22of the bolt10, and the threaded shaft portion16is disposed between the head14and the frangible pintail12. As shown inFIG. 1, initially the frangible pintail12and threaded shaft16is inserted through apertures24,26provided in two or more work pieces28,30, and a collar32is slid onto the bolt10, positioned proximate the threaded shaft16. Then, as shown inFIG. 2, an installation tool40is engaged with the collar32and the frangible pintail12. Specifically, as shown inFIG. 3, jaws41of the installation tool40grip and pull on the pintail12(as represented by arrow42) while an anvil43of the installation tool40pushes down on the collar32(as represented by arrows44), causing the collar32to swage down onto the bolt10. The swaging causes the collar32to deform and generally grip onto the threaded shaft portion16of the bolt10. Once the collar32has been swaged, the pintail12continues to be pulled until it breaks off, as shown inFIG. 4, leaving the bolt10installed in the work pieces28,30, secured by the collar32. Similarly, if the lockbolt is provided as being of the type which does not include a frangible pintail, the threaded portion of the bolt is gripped and pulled as the collar is swaged, and once the collar has been fully swaged, the bolt is released leaving the threads undamaged.

Such lockbolts and tools for installing such lockbolts are generally known in the art. For example, a typical tool for installing lockbolts with frangible pintails is disclosed in U.S. Pat. No. 2,114,493, and includes an anvil for swaging the collar and jaws for gripping and pulling on the pintail.

The threads of some prior art lockbolts, such as that which is shown inFIGS. 1-4, are helical. Regardless of whether the lockbolt includes a frangible pintail or not, the helical threads provide that once the lockbolt has been installed (i.e., the collar has been swaged onto the bolt), the collar can be rotated off of the lockbolt, and thereafter can be threaded back on to the lockbolt (or a new nut threaded onto the lockbolt). A problem associated with providing a lockbolt having standard helical threads is that the collar, once swaged onto the lockbolt, is susceptible to vibrating loose.

U.S. Pat. No. 2,531,048 discloses a lockbolt which tends to solve this problem. The lockbolt, instead of including standard helical threads, includes annular ribs. Being annular rather than helical provides that once a collar is swaged onto the ribs, the collar is not susceptible to vibrating loose. However, the lockbolt presents a new disadvantage: once a collar is swaged onto the ribs, the collar must be broken off of the ribs, rather than be rotated off the ribs. As such, the collar cannot be removed and rotated back onto the lockbolt. In fact, due to the ribs being annular, even a new collar cannot be threaded onto the lockbolt. Instead, the swaging process must be repeated to re-secure the lockbolt.

OBJECTS AND SUMMARY

An object of an embodiment of the present invention is provide a lockbolt which provides that, after installation, a collar does not tend to vibrate loose, yet the collar can be selectively rotatably removed and re-installed on the lockbolt.

Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a lockbolt which includes a head portion and a shaft which extends from the head portion. The shaft includes at least a portion which is threaded and has a multi-lobular profile. A collar is swageable onto the multi-lobular threaded portion, and thereafter the lobes or high points provide that the collar does not tend to vibrate loose from the threading. The fact that the section which has a multi-lobular profile is also threaded provides that the collar can be selectively rotatably removed and re-installed on the lockbolt (or that a conventional threaded nut can be installed on the lockbolt once the swaged collar has been removed). Before swaging, the collar may initially include a cylindrical bore, or a bore which is multi-faceted, preferably generally corresponding to the profile of the multi-lobular portion of the lockbolt. The lockbolt may also include a frangible pintail, wherein the multi-lobular threaded portion is disposed between the head portion of the bolt and the frangible pintail. The frangible pintail may be provided as having annular ribs. Alternatively, the frangible pintail may be provided as having the same threading as the multi-lobular threaded portion of the lockbolt.

DESCRIPTION

While the present invention may be susceptible to embodiment in different forms, there are shown in the drawings, and herein will be described in detail, embodiments thereof with the understanding that the present description is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to that as illustrated and described herein.

FIGS. 5 through 7illustrate a lockbolt100which is in accordance with an embodiment of the present invention. The lockbolt100is similar to the prior art lockbolt10shown inFIGS. 1 through 4in that the lockbolt100includes a head102, a threaded shaft104and a frangible pintail106having annular ribs108, wherein the head102is at one end110of the bolt100, the frangible pintail106is at the other end112of the bolt100, and the threaded shaft portion104is disposed between the head102and the frangible pintail106. The difference between the lockbolt100shown inFIGS. 5 through 7and the prior art lockbolt10shown inFIGS. 1 through 4resides in the fact that in the lockbolt100shown inFIGS. 5 through 7, the threaded shaft portion104is not merely helically threaded, but rather includes a threaded portion which is multi-lobular or multi-faceted, meaning that the thread includes high points114and low points116as shown inFIGS. 8-10.

For example, the threading may be provided as having five lobes or high points (such as is shown inFIGS. 8-10), such as an HP-5 thread as disclosed in U.S. Pat. Nos. 3,875,780 and 3,935,785, both of which are incorporated herein by reference in their entirety. Alternatively, the threading may be provided as having a number of lobes which are more or less than five. For example, the threaded portion may be provided as being quad-lobular (i.e., having four high points), tri-lobular (i.e., having three high points), an oval (i.e., having two high points), etc.

Regardless, the fact that the threaded portion104of the lockbolt100is multi-lobular, having high points and low points, provides that a collar120, once swaged onto the lockbolt10, does not tend to vibrate off. This is because vibration alone is not enough to cause low points122of the swaged collar120(seeFIG. 10) to move past high points114of the multi-lobular portion104of the lockbolt100. Simultaneously, the fact that the threaded portion104is, in fact, threaded and multi-lobular, provides that a collar120can be intentionally rotated off the lockbolt100, if desired, by using a tool to apply enough torque to the collar120.

FIGS. 5 through 7illustrate installation of the lockbolt100. The installation process is quite similar to the installation process which is used to install the lockbolt10shown inFIGS. 1 through 4. To install the lockbolt100shown inFIGS. 5 through 7, Textron Fastening Systems' Hydro-Electric Power Tool, Model T30 73412-02000, along with Textron Fastening Systems' HydraPac Hydraulic Power Unit, Model HP21 73401-02000, Model HP41 73400-02000 or Model HP51 73404-02000, can be used. Alternatively, some other appropriate installation tool can be used.

Initially, the frangible pintail106and threaded shaft104is inserted through apertures24,26provided in two or more work pieces28,30, and a collar120is placed on the lockbolt100, proximate the multi-lobular threaded portion104. As shown inFIG. 8, the collar120can be provided as initially having a throughbore130which is multi-lobular or multi-faceted. Preferably, the collar120is provided as having a throughbore130which has a profile which corresponds to the profile of the multi-lobular portion104of the lockbolt100. In other words, if the multi-lobular portion104of the lockbolt100is provided as having five lobes or high points (such as an HP-5 thread), preferably the collar120is provided as having a throughbore130which has five high points131as well. The fact that the collar120is provided as having a throughbore130which has a profile which corresponds to the profile of the multi-lobular portion104of the lockbolt100provides for uniform deformation of the collar120during swaging.

Additionally, the fact that the collar120is provided as having a throughbore130which has a profile which corresponds to the profile of the multi-lobular portion104of the lockbolt100provides that the collar120can assist with regard to installation. Specifically, the collar can be placed on the bolt and rotated slightly so that there is an interference fit between portion104and the throughbore130of the collar. Then, an installation tool can be brought into engagement with the pintail106and collar120to perform the swaging operation. Alternatively, as shown inFIG. 9, the collar120can be provided as initially having a throughbore130which is cylindrical, or some other shape.

Regardless, as shown inFIG. 5, an installation tool140is engaged with the collar120and the frangible pintail106. Specifically, jaws142of the installation tool140grip and pull on the pintail106while an anvil144of the installation tool140pushes down on the collar120, causing the collar120to swage down onto the bolt100, as shown inFIG. 6. The swaging causes the collar120to deform and generally lock down onto the multi-lobular threaded portion104of the bolt100(FIG. 10provides a view (similar to a cross-sectional view)) of the collar120swaged down onto the multi-lobular portion104of the lockbolt100.

Preferably, the installation tool140swages only a portion150of the collar120down onto the threaded portion104(seeFIG. 6) while the remaining portion152remains unswaged, as this renders the assembly easier to assemble and manufacture. Preferably, the portion152of the collar120which is not swaged includes a hex profiled surface154such that a standard hex tool can be used to subsequently remove the collar120. Once the collar120has been swaged, the pintail106continues to be pulled until it breaks off, as shown inFIG. 7, leaving the bolt100installed in the work pieces28,30, secured by the collar120. Similarly, if the lockbolt is of the type which does not include a frangible pintail, the threaded portion of the bolt is gripped and pulled as the collar is swaged, and once the collar has been swaged, the bolt is released.

Once the collar120has been swaged on the lockbolt, and the lockbolt100fully installed, secured by the collar120, the collar120will not tend to vibrate off, due to the multi-lobular profile of the threaded portion104. Specifically, vibration alone will not tend to provide that low points122of the collar120can overcome high points114of the multi-lobular portion104of the lockbolt100, as shown inFIG. 10. In other words, the multi-lobular profile of portion104provides a certain amount of prevailing torque which tends to resist rotation in response to vibration. At the same time, the collar120can be intentionally removed merely by using a tool to apply enough torque (such as by using a hex tool to apply a torque to surface154) such that the low points122of the collar120overcome the high points114of the multi-lobular portion104of the lockbolt100.

Once the collar120has been swaged onto the lockbolt100, intentional removal of the collar120(i.e., rotation of the collar120using a tool) causes a thread to be formed in the throughbore130of the collar. The thread which is formed in the collar120provides that the collar120can be easily rotated back onto the threaded portion104of the lockbolt100after the collar120has been intentionally removed therefrom. Subsequently, once the collar120has been rotated back onto the lockbolt100, it is expected that the fact that the threaded portion104of the lockbolt is multi-lobular will result in the collar120not tending to vibrate off as much as if the threaded portion104of the lockbolt100were to be provided as being helically-threaded with standard helical threads, as is provided in the prior art (i.e., lockbolt10as shown inFIGS. 1-4). In other words, there is a certain amount of prevailing torque which exists over and beyond what would be provided if portion104had a standard helical thread.

While it was discussed above that the collar120is preferably initially provided with a hex surface154to facilitate removal of the collar120with a hex tool, the collar120can also initially be provided without such a surface, and such a surface can be formed on the collar120, by the anvil144of the installation tool140during the swaging operation.

FIG. 11illustrates a lockbolt200which is in accordance with an alternative embodiment of the present invention. The lockbolt200is very similar to the lockbolt100shown inFIG. 5 through 7, the only difference being that the frangible pintail202does not include annular ribs, but rather provides a multi-lobular threaded profile similar to the multi-lobular portion104of the lockbolt200(or lockbolt100). This way, both the portion104of the lockbolt which ultimately receives the collar and the pintail portion202can be threaded at the same time, using the same thread-forming process. Alternatively, the pintail can be provided as having a helical, non-lobular thread.

While embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the disclosure.