Patent Application
20060075617
One aspect of the invention generally relates to tools and methods for removing installed nut plates, and another aspect generally relates to tools and methods for conditioning holes in workpieces, such as for conditioning a hole before installing a nut plate.
Fasteners used in association with fluid tanks, such as fuel tanks or water tanks, for aircraft or the like present a problem in preventing leakage through the openings for the fasteners. Fasteners used in such installations may include a nut plate and a nut which are part of an assembly. There are many different design configurations of nut plates being used today. Two major classes are riveted nut plates and rivetless nut plates.
In riveted nut plates, two rivets are employed for attaching the body of the nut plate to the workpiece. To eliminate the potential for leakage, sealant is used between the structure and the nut plate.
With regard to rivetless nut plates, some designs provide that a sleeve is flared against a workpiece. One example of this type of rivetless nut plate is disclosed in U.S. Pat. No. 4,732,518, which is hereby incorporated herein by reference in its entirety. The '518 patent illustrates the insertion of a sleeve inside a workpiece against heavy interference forces and then deformation of the sleeve to produce flaring of the end of the sleeve. The sleeve has a serration/lobe configuration thereon with the serration/lobe configuration being long and tapered such that the serrations/lobes extend into the walls of the workpiece. The tapered feature, length and specific geometry are necessary to make installation possible with the method of installation which was chosen for its application. The main object of the '518 patent with its tapered and extended serration/lobe configuration was to enhance the fatigue life of the workpiece by distributing the load throughout the workpiece and providing expansion due to the insertion of the sleeve into the workpiece, and to cold work the material adjacent the perimeter of the workpiece aperture.
Other nut plate designs do not rely on flaring of the sleeve. U.S. Pat. Nos. 5,096,349, 5,245,743, 5,405,228 and pending U.S. application Ser. No. 10/272,721 (filed Oct. 17, 2002) and Ser. No. 10/929,701 (filed Aug. 30, 2004) disclose rivetless nut plate designs which do not rely on flaring of the sleeve, and these five items are hereby incorporated herein by reference in their entirety. While some rivetless nut plate designs rely on adhesive for attaching the nut plate to the structure, the designs disclosed in the five items cited above rely on heavily cold-worked holes and high interference engagement utilizing a hardened pin as the installation tool to expand a sleeve element into engagement with a workpiece structure. Because of high level expansion, the friction forces created are intended to retain the nut plate and provide expected mechanical properties.
Once installed, most rivetless nut plates are removed by drilling out the flared sleeve portion, or by drilling out the rivets while holding the nut plate. Drilling out the rivets and the sleeve from the holes requires a special skill. The procedure, aside from being cumbersome and time consuming, leaves behind contaminating metal chips. Additionally, it often enlarges the hole size requiring an oversized nut plate for replacement. Safety considerations, for drilling out the old nut plate, are required to prevent damage to surrounding structure and the operator.
An object of an embodiment of the present invention is to provide an improved tool and method for removing installed rivetless nut plates, either manually or by using a power tool.
Another object of an embodiment of the present invention is to provide a tool and method for conditioning a hole, such as before installation of a rivetless nut plate.
Briefly, and in accordance with at least one of the foregoing objects, one aspect of the present invention provides a tool for removing a nut plate after the nut plate has been installed in an aperture in a workpiece.
A first embodiment of the present invention provides a tool which is configured to be used in association with a power tool to remove the nut plate from a nut side of the nut plate. Specifically, the tool includes a nosepiece which is configured to be engaged with a power tool. During removal of the nut plate, the nosepiece is pressed against the workpiece such that the nut plate is disposed in an opening provided in the nosepiece. A mandrel with serrations is inserted through the nut plate and the nosepiece, and is inserted into the power tool. The power tool is thereafter actuated to grip the serrations on the mandrel and pull on the mandrel until a head of the mandrel contacts and pulls on the nut plate, causing the nut plate to dislodge from the aperture in the workpiece.
A second embodiment of the present invention is similar to the first embodiment, but provides a tool which is specifically configured for manual use (i.e., for operation by hand rather than for use with a power tool). The tool includes a base which is positioned over the installed nut plate. A mandrel with threads is inserted through both the nut plate and base and is threaded into a threaded insert which is retained in a knob. Then, the knob is rotated which causes the mandrel to effectively retract into the knob, causing the head of the mandrel to pull on the nut plate and dislodge the nut plate from the aperture in the workpiece.
A third embodiment of the present invention provides a tool which is configured to be used in association with a power tool to remove the nut plate from a bolt side of the nut plate. Specifically, the tool includes a nosepiece which is configured to be engaged with a power tool. During removal of the nut plate, the nosepiece is pressed against a sleeve of the nut plate. On the other side of the workpiece, a mandrel with serrations is inserted through a sleeve which is pressed against the workpiece. The mandrel is inserted through the sleeve, through the nut plate, through the nosepiece, and into the power tool. The power tool is then actuated to grip the serrations on the mandrel and pull on the mandrel until a head of the mandrel contacts the sleeve after which time further pulling on the mandrel by the power tool causes the nosepiece to push on the sleeve of the nut plate, causing the nut plate to dislodge from the aperture in the workpiece.
A fourth embodiment of the present invention is similar to the third embodiment, but provides a tool which is specifically configured for manual use (i.e., for operation by hand rather than for use with a power tool). The tool includes a base which is positioned over the installed nut plate. A mandrel with threads is retained by the base, and is inserted through the nut plate, through a nosepiece and nosepiece support, and is threaded into a threaded insert in a knob. Then, the knob is rotated which causes the mandrel to effectively retract into the knob, causing the nosepiece to push on the sleeve of the nut plate, causing the nut plate to dislodge from the aperture in the workpiece.
Another aspect of the present invention provides a tool for conditioning a hole, such as for conditioning a hole prior to installing a nut plate. The tool includes a mandrel having serrations as well as a rim on the underside of its head, and a nosepiece which has a rim on its facing surface. The nosepiece is configured for threadable engagement with a power tool and for contacting a workpiece, such that the rim on the facing surface surrounds the hole. The mandrel is extended through the hole and the nosepiece and inserted into the power tool, such that the rim on the underside of the head of the mandrel contacts the workpiece and surrounds the hole. As such, the rim on the nosepiece is pressed against one side of the workpiece and the rim on the mandrel is pressed against the other side of the workpiece. Then, the power tool is actuated to grip and pull on the mandrel, causing the rims to be pulled toward each other, thereby applying a compressive force to the workpiece in the area around the holes, causing the area of the workpiece surrounding the hole to reshape and become fatigue enhanced. The reshaping actually causes the hole to become smaller.
The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which:
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.
One aspect of the present invention involves providing an improved tool and method for removing an installed rivetless nut plate, either manually or by using a power tool, such as a rivetless nut plate as disclosed in U.S. application Ser. No. 10/272,721 (filed Oct. 17, 2002) and Ser. No. 10/929,701 (filed Aug. 30, 2004), both of which have been incorporated herein by reference in their entirety.
Specifically,
As discussed,
As shown in
During removal of the nut plate 130, the nosepiece 128 is pressed against the workpiece 128 (i.e., the end surfaces 126 of the arms 122 of the nosepiece 102 are pressed against the workpiece 128) such that the nut plate 130 is disposed in the opening 124 between the arms 122. The end 144 of the mandrel 136 which is proximate the serrations 140 is inserted through the nut plate 130, from the other side of the workpiece 128, through the bore 108 provided at the end 106 of the nosepiece 102 and into the power tool 118 such that the head 138 of the mandrel 136 is held flush against the nut plate 130. The power tool 118 is then actuated to grip the serrations 140 on the mandrel 136 (i.e., jaws in the power tool 118 grip the serrations 140) and pull on the mandrel 136 until the head 138 of the mandrel 136 contacts and pulls on the nut plate 130, as shown in
The tool 200 illustrated in
The tool 200 also includes a knob 210 which has a threaded insert 212 disposed in a bore 214. The knob 201 also includes a plurality of finger grip portions 216 which facilitate gripping and rotating the knob. A mandrel 218 having an enlarged head portion 220 and threads 222 on a shaft portion 224 is also provided.
During removal of the nut plate 130, the base 202 is pressed against the workpiece 128 (i.e., the end surfaces 226 of the arms 203 of the base 202 are pressed against the workpiece 128) such that the nut plate 130 is disposed in the opening 208 between the arms 203. The end 228 of the mandrel 218 which is proximate the threads 222 is inserted through the nut plate 130, from the other side of the workpiece 128, through the bore 206 provided in the base 202 such that the head 220 of the mandrel 218 is held flush against the nut plate 130, and is threaded into the threaded insert 212 in the knob 210. Then, the knob 210 is rotated. As the knob 210 is rotated, the mandrel 218 effectively retracts into the knob 210, as shown in
The tool 300 illustrated in
The tool 300 also includes a base component 318 which is generally cylindrical having a base portion 320 and a cylindrical side wall 322 which extends from the base portion 320 and provides an opening 324, such that the base component 318 is generally cup-like. A bore 326 is provided in the base portion 320, generally at its center. The cylindrical side wall 322 includes a surface 328 which, as will be described, is pressed against the workpiece 128 during removal of the nut plate 130 from an aperture 132 in the workpiece 128. A mandrel 136 having an enlarged head portion 138 and serrations 140 on a shaft portion 142 is also provided.
During removal of the nut plate 130, the base component 318 of the tool 300 is pressed against the workpiece 128 such that the nut plate 130 is disposed in the opening 324. The end 144 of the mandrel 136 which is proximate the serrations 140 is inserted through the bore 326 in the base 320, through the nut plate 130, through the nosepiece 302, and into the power tool 118 on the other side of the workpiece 128 such that the head 138 of the mandrel 136 is in contact with the base component 318. The power tool 118 is then actuated to grip the serrations 140 on the mandrel 130 (i.e., jaws in the power tool 118 grip the serrations 140) and pull on the mandrel 136, causing the end surface 316 of the nosepiece 302 to push on the nut plate 130, as shown in
The tool 400 illustrated in
The tool 400 also includes a nosepiece member 410 and a nosepiece support 412 which is configured to retain and support the nosepiece member 410. The nosepiece support 412 is generally cylindrical having a threaded opening 414 for threadably receiving a corresponding externally threaded portion 418 on the nosepiece 410. The nosepiece 410 includes a throughbore 420, as well as an outwardly extending cylindrical portion 422 which has an end surface 424 which is configured to engage and push on an installed nut plate 130. The tool 400 also includes a knob 426 which has a threaded insert 428 disposed in a bore 430. The knob 426 also includes a plurality of finger grip portions 432 which facilitate gripping and rotating the knob 426.
During removal of the nut plate 130, the mandrel 218 is extended through the nut plate 130, the nosepiece 410 and the nosepiece support 412, and the knob 426 is rotated such that the threaded portion 222 of mandrel 218 threads into the threaded insert 428 in the knob 426. As the knob 426 is rotated, the mandrel 218 effectively retracts into the knob 426, causing the base 402 to be pulled toward the workpiece 128, causing the end surface 424 of the nosepiece 410 to push on the nut plate 130, as shown in
The version of the tool 100, 200, 300, 400 (i.e., that which is shown in
Typically, when a rivetless nut plate is removed, the circumferential edge of the hole is deformed with a minor countersink and the hole itself is slightly enlarged. Another aspect of the present invention provides a tool for conditioning a hole, such as for conditioning a hole prior to reinstalling another nut plate. Specifically, the tool eliminates the minor countersink, effectively repairs the circumferential edge of the hole, conditions the inner walls of the hole, and reduces the hole size while introducing compressive residual stress into the workpiece area surrounding the hole.
As shown in
As shown in
As shown in
The tool 500 introduces compressive residual stresses in the structure surrounding the hole that is being conditioned. The structure inside the hole is compressed by the plug section 510 of the mandrel 502. The top edge of the hole is compressed by the rim 530 of the nosepiece 520. All of these compressive forces help to negate some of the tensile stress concentrations that appear in the structure naturally due to the hole in the structure. The overall result is lowered stresses at the hole, which leads to a strengthened structure.
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.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/616,722, filed Oct. 7, 2004, which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60616722 | Oct 2004 | US |
