The present invention relates to bolting arrangements wherein two flanges are bolted together. More particularly, the present invention relates to bolting arrangements in which bolt bending resulting from relative movement of the flanges is minimized.
Flanges are generally bolted together by inserting bolts through bolt holes provided in each of the flanges and that are aligned with each other. Such bolted flanges usually remain in their bolted condition, because a number of connecting bolts are generally provided to securely hold the bolted flanges together. However, the imposition of large radial, tangential, or axial loads on one or both components to which the respective flanges are secured can impose on the connecting bolts bending moments or tensile forces that can cause deformation or rupture of the bolts.
For example, unusual and sometimes large loads can be applied to bolted flanges in turbomachines, where pairs of flanged end casings are commonly bolted together. In aircraft gas turbine engines that have axial flow fans or axial flow compressors, rotor blade failures, which can be caused by foreign object damage to fan or compressor blades resulting from foreign objects that are drawn into the fan or compressor, can cause rotor unbalance conditions. Such rotor unbalance conditions can impose radial, circumferential, and possibly also axial loads that can shift the positions of the flanges radially relative to each other, circumferentially relative to each other, or axially relative to each other. In either event, unintended high shear, bending, or tensile loads, or a combination of such loads, can be applied to the flange connecting bolts, leading to bolt deformation, and possibly to bolt rupture and separation of the bolted casings from each other. Casing separation at the bolted flanges is an undesirable condition, and the present invention is directed to avoiding flange bolt failures by minimizing bending and axial stresses imposed on flange connecting bolts when the flanges are subjected to relative movement with respect to each other as a result of external loads applied to the components to which the flanges are connected.
Briefly stated, in accordance with one aspect of the present invention, there is provided a bolting arrangement in which two-piece washers are provided to allow pivotal movement of the connecting bolts at a flanged connection. The washers include a first annular washer element having oppositely-facing major annular faces and having a first washer element central axis. One major annular face of the first washer element is defined by a convex surface. A second annular washer element having oppositely-facing major annular faces and having a second washer element central axis is also provided. One major annular face of the second washer element is defined by a concave surface. The convex surface and the concave surface are in surface-to-surface contact with each other and are movable relative to each other so that their respective axes can assume non-coaxial positions.
The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which:
Referring now to the drawings, and particularly to
Similarly, a second annular casing has a casing wall 28 that terminates at an outwardly-extending radial flange 30 that includes a plurality of throughbores 32 (only one of which is shown in
As shown in
Referring now to
The two-piece washer includes a first annular washer element 42 that has a flat annular face 44 at one annular end and a convex annular face 46 on the opposite annular end. Additionally, the diameter of inner opening 48 of first washer element 42 can be substantially equal to the diameter of bolt shank 18.
A second annular washer element 50 also has a flat annular face 52 at one annular end, and a concave annular face 54 on the opposite annular end. Additionally, the diameter of inner opening 56 of second washer element 50 can be substantially larger than the diameter of bolt shank 18, to accommodate bolt tilt under severe loading conditions and thereby avoid bolt contact with inner opening 56.
The curvature of convex annular face 46 of first washer element 42 can be substantially the same as the curvature of concave annular face 54 of second washer element 50. The curvatures are selected to allow relative sliding movement to occur between the curved faces of first and second washer elements 42, 50 when the curved faces are placed in contacting relationship, as shown in
Also shown in
The foregoing description of the invention is presented in the context of bolting together two flanges. However, the disclosed bolting technique and the disclosed two-piece washers can also be utilized in the bolting together of components other than flanges. Moreover, the flanges need not be annular flanges—they can alternatively be linear flanges. And the movement of the respective parts relative to each other as shown in
Although particular embodiments of the present invention have been illustrated and described, it would be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the invention.
Number | Name | Date | Kind |
---|---|---|---|
2308745 | English | Jan 1943 | A |
3171518 | Bergmann | Mar 1965 | A |
3174386 | Lewis | Mar 1965 | A |
3220289 | Farekas | Nov 1965 | A |
3220389 | Van Rinsum et al. | Nov 1965 | A |
3749362 | O'Connor et al. | Jul 1973 | A |
4225264 | Coone | Sep 1980 | A |
4620264 | Ushifusa et al. | Oct 1986 | A |
4640537 | Chaix et al. | Feb 1987 | A |
4781006 | Haynes | Nov 1988 | A |
4830557 | Harris et al. | May 1989 | A |
5037258 | Heurteux | Aug 1991 | A |
5263997 | Parker et al. | Nov 1993 | A |
5451116 | Czachor et al. | Sep 1995 | A |
5802129 | Deaver et al. | Sep 1998 | A |
6131962 | Jensen et al. | Oct 2000 | A |
6176663 | Nguyen et al. | Jan 2001 | B1 |
6250041 | Seccombe | Jun 2001 | B1 |
6364564 | Chaniot et al. | Apr 2002 | B1 |
6374665 | Somppi et al. | Apr 2002 | B1 |
Number | Date | Country | |
---|---|---|---|
20040101384 A1 | May 2004 | US |