Many designs require close tolerances in attachment hole alignment at attachment points in articles to be assembled to achieve proper fit of the articles and insure the proper transference of shear loads at the attachment points. In general, close tolerance hole fabrication and inspection thereof becomes increasingly difficult as tolerances become tighter and geometric complexity is increased. In many instances, conventional fabrication techniques prove impractical or impossible for tight tolerancing and complex geometries.
Various methods have been proposed for accurately aligning attachment holes of articles to be assembled or compensating for misalignment of such holes. One such proposed method is custom or matched machining. Custom or matched machining permits the fabrication of very accurately aligned holes in a single matched set of articles to be assembled.
The use of custom and matched machining provides matched sets of articles to be assembled having accurately aligned holes. However, such matched sets do not lend themselves well to be interchanged when maintenance or repair of the articles is necessary. Further, custom and matched machining is expensive when high volumes are needed.
Another proposed method utilizes a master fixture on which all parts are fabricated. The use of a master fixture provides for interchangeability between the articles to be assembled. However, the use of a master fixture does not permit the implementation of close tolerances in some situations where the geometry of the articles is complex. Further, line to line fits necessary for maximum load transference at the point of attachment are not practical by use of a master fixture. Still further, master fixtures are expensive and require constant damage and wear monitoring and control.
Yet another proposed solution to the misalignment problem described above is to provide a device which permits the adjustment of the location of the fasteners used to assemble the articles to compensate for misalignment of the attachment holes. Such devices are shown in U.S. Pat. Nos. 1,097,185; 1,704,939; 3,866,938; 4,420,272; 4,561,796 and 4,830,529 and Australian Patent 81,766/75.
U.S. Pat. No. 1,097,185 discloses a coupling bolt combined with an integral eccentric collar which has an eccentric bore for the reception of the body of the bolt. The apparatus disclosed in U.S. Pat. No. 1,097,185 compensates for misalignment by permitting the eccentric collar to be rotated.
The apparatus disclosed by U.S. Pat. No. 1,097,185 suffers from various disadvantages. Namely, the eccentric collar when rotated causes relative movement between the articles being assembled. Thus, exact location of the articles relative to each other is not possible. Further, movement of the eccentric collar is highly detrimental to the assembled articles when multiple eccentric collars are used and where load sharing is essential.
U.S. Pat. No. 1,704,939 discloses an eccentric bushing which is used to assemble articles wherein the eccentric bushing is disposed within a hole in one of the articles. The eccentric bushing includes a body and a hole set eccentrically in the body. Adjustments for misalignment are accomplished in the eccentric bushing disclosed by U.S. Pat. No. 1,704,939 by rotating the bushing.
The eccentric bushing disclosed by U.S. Pat. No. 1,704,939 can only accommodate limited cases of misalignment. Further, if three or more inserts are used alignment may not be possible due to insufficient degrees of freedom offered by the combined eccentric bushings. Still further, the eccentric bushing disclosed by U.S. Pat. No. 1,704,939 suffers from the same disadvantage as the apparatus disclosed by U.S. Pat. No. 1,097,185. Namely, rotation of the bushing causes relative movement between the articles being assembled. Such relative movement between the articles being assembled makes for the exact positioning of the articles relative to each other impossible.
The adjusting device disclosed in U.S. Pat. No. 3,866,938 provides an eccentric bushing similar to that disclosed in U.S. Pat. Nos. 1,097,185 and 1,704,939. Thus, the adjusting device taught by U.S. Pat. No. 3,866,938 suffers from the same disadvantages described above relative to U.S. Pat. Nos. 1,097,185 and 1,704,939.
U.S. Pat. No. 4,420,272 discloses dual eccentric bushings which are used to compensate for misalignment. The dual eccentric bushings are locked in a fixed position by the use of a snap ring.
The dual eccentric bushings disclosed by U.S. Pat. No. 4,420,272 suffers from the disadvantage of not providing simple and easy to use apparatus for fixing the position of the eccentric bushings relative to each other. The snap ring is difficult to use in areas of limited access. Also the dual eccentric bushings disclosed in U.S. Pat. No. 4,420,272 does not provide for the proper transference of load forces at the attachment points of the articles being assembled.
U.S. Pat. No. 4,561,796 provides a tamper proof clamping device which provides for radical adjustment thereof. The device disclosed by U.S. Pat. No. 4,561,796 suffers the disadvantage of being cumbersome and difficult to use. Further, the device disclosed by U.S. Pat. No. 4,561,796 does not provide for lateral alignment.
U.S. Pat. No. 4,830,529 discloses an adjustment device for fixing an object against a supporting surface wherein two sets of mutually perpendicular slides allow transverse adjustment. The device disclosed by U.S. Pat. No. 4,830,529 suffers from the disadvantage of not providing for the transference of load forces at the attachment points of the articles being assembled. Also, the device disclosed by U.S. Pat. No. 4,830,529 does not provide apparatus for securely locking the device in a fixed position relative to the articles being assembled.
Australian Patent 81,766/75 discloses a dual eccentric misalignment compensating device. The dual eccentric misalignment compensating device disclosed by Australian Patent 81,766/75 suffers from the disadvantage of not providing for the proper transference of load forces at the attachment points of the articles being assembled. In addition, Australian Patent 81,766/75 suffers from the disadvantage of requiring the use of a retention device to retain the eccentric inserts together once assembled.
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