Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Headed fastener element with nut – washer – securing means or cap – Deformable securing means
Reexamination Certificate
2002-05-23
2004-04-13
Saether, Flemming (Department: 3679)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Headed fastener element with nut, washer, securing means or cap
Deformable securing means
C411S335000
Reexamination Certificate
active
06719510
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fasteners, and more particularly to a fastener including a bolt and a threaded swageable collar.
BACKGROUND OF THE INVENTION
A type of fastener widely utilized in the aerospace industry typically comprises a bolt having a head, shank and pin tail portions. The shank portion extends through aligned apertures formed in adjacent panels, wherein the shank portion typically includes a single gripping ledge formed thereon. A collar is swaged onto the shank portion in a manner such that the collar is secured to the gripping ledge in place against a surface of one of the panels.
The male fastener, also called a “stud” or “bolt”, is designed to be reusable such that the swaged-on collar the female part of this fastening system is removed by using a special tool. The removal process implies destroying the swaged-on collar by a tool having two jaws that forces the collar end to break open. During the removal process the single gripping ledge on the male fastener could be damaged thus preventing the fastener stud from being reused. The existing conventional fastener using a swaged-on collar was improved by the present applicant as shown in U.S. Pat. Nos. 5,669,746 and 6,019,559 which disclose a fastener comprising a head portion, a flange portion, a shank portion which extends through aligned apertures formed in adjacent panels, and a collar swaged on the shank portion of the fastener. The shank portion comprises a plurality of gripping surfaces having angled surfaces formed between a plurality of spiral grooves. The female part of this fastening system, named “collar” is first positioned over the end of the shank portion and an installation tool then swages the collar thereon. The collar is tightly held by multiple gripping surfaces, thereby preventing movement in the direction of the longitudinal axis of the fastener. When the collar is swaged onto the fastener shank portion, mating spiral grooves are formed along the interior surface of the collar. It is important to mention that in the existing fastener as well as in the one described by the above mentioned patents, the male fasteners (stud) is used in the installation process as a forming tool, intended to form the spiral groove into the collar. In order for the installation to be successful and meet all application requirements, the bolt needs to be manufactured from a material much harder than the collar material.
In order to remove the collar from the fastener shank portion, a tool having pivotal jaw members is positioned in the space formed between the bottom surface of the shank portion and the overhanging portion of the swaged collar, the jaw members being forced apart which, in turn, forces the collar to expand outwardly from the shank portion. During this expansion, the collar material is supposed to fracture, exposing the tail portion of the bolt. A tool then engages the collar, the collar being removed when the tool rotates, or spins, in the clockwise direction, pushed out by the helical groove formed in the collar by the male fastener at installation. The process of collar removal after it has been forced open, can be best described as “threading the collar out”. The fastener disclosed in these patents provided a swaged collar to be quickly and easily removed while not damaging the gripping surfaces formed on the fastener shank portion, thus increasing the fastener reusability and decreasing the disassembly down time, in turn providing significant cost savings.
However, under certain performance criteria the prior art fastener described in the above mentioned U.S. patents was subject to problems. Specifically when the male fastener (stud) material was not hard enough, or was subjected to temperatures beyond the transformation point of the fastener material, as high as 2300° F., the performance of the fastener could not meet the application requirements. Such applications exist when used, for example, in the exhaust systems for F-22 engines. The prior art fastener design was also highly susceptible to operator errors during installation, and the installation pre-load could not be controlled, causing rejections and excessive re-work. During the removal process, after being split open by a special tool, the collar needs to be pushed out of the stud, by using the spiral grooves formed inside of the collar during the installation process. In some cases, especially when the stud material is softened by exposure at high temperatures, the spiral groove is not formed well enough to give a positive axial force towards unthreading the collar, stripping before the collar is pushed out of the stud. In cases like this, the collar needs to be removed by other means, and in the removal process the stud may get damaged. Other problems with the prior art design included low or no re-usability because of the potential problems described previously, low or no pre-loads, faulty installations due to tool misalignment with the fastener during installation and a high standard of deviation of the load capability of the installed fastener.
Therefore, it is desired to provide an improved fastener which incorporates a threaded swageable collar which eliminates the problems associated with previous designs and is usable even when manufactured from softer, lighter materials, and in all conditions such as, for example, in temperatures beyond the transformation point.
SUMMARY OF THE INVENTION
As shown in
FIGS. 1 and 2
, the present invention provides an improved fastener comprising a male part of the system
12
, named bolt or stud (depending on the application) having a head portion, a flange portion, a shank portion capable of extending through aligned apertures formed in adjacent panels, and a female part of the system
14
, a threaded collar for receipt on the shank portion of the fastener. The shank portion of the male fastener presents a high strength thread
22
to provide a plurality of gripping surfaces having angled surfaces form between a plurality of spiral grooves. The female part of the system, named “collar” has a plurality of mating internal threads
36
and is positioned over the end of the shank portion and threaded onto the shank until a certain installation torque is reached, accurately controlling the installation pre-load of the fastener. The end of the collar is then swaged over a locking groove
26
on the end of the shank to positively lock the collar
14
onto the shank of the stud
12
.
The threaded portion
22
on the shank of the male part
12
of the fastening system, in combination with the internal threads
36
on the collar
14
provides the desired installation pre-load and the majority of the axial load capability. By comparison, on the previous art fastener, the load carrying capability was given by both the spiral groove and by the swaged portion at a ratio of almost 50% each. Because of this, in cases when the stud material was softened by exposure to very high temperatures, the installed system lost almost a half of the load capability. It also provides the axial force required during the removal of the collar. The length of the threaded portion
22
of the male part of the fastening system (stud or bolt) is established by the maximum designed grip range. The locking groove
26
on the end of the shank is designed to provide good material flow during swaging. A locking shoulder
28
is positioned behind the groove and is designed to provide maximum anti-rotational resistance of the collar after installation, as well as easy removal of the collar
14
.
Likewise, as shown in
FIG. 2
, the length of the threaded portion
36
on the internal diameter of the collar is established by the load requirements and is constant for different grip ranges. The length of the swaging portion
38
of the collar
14
is directly dependent on the design maximum grip capability (thickness of the panels to be fastened) of the fastening system. The material thickness of the swaging portion
38
is computed such as to provide the desired anti-rotational, vibratory and axial load res
Christie Parker & Hale LLP
Huck Patents, Inc.
Saether Flemming
LandOfFree
Self-locking fastener with threaded swageable collar does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Self-locking fastener with threaded swageable collar, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Self-locking fastener with threaded swageable collar will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3262358