Spring loaded bushed wedgelock

Abstract: The wedgelock of the present invention prevents the separation of structural members during drilling or other fabrication operations on structural assemblies with curved surfaces or thickness variations and precludes the formation of burrs and delaminations which might result from such separation. The wedgelock also permits more precise and repeatable hole and other feature fabrication by more precisely locating an alignment fixture, such as a drill plate, relative to a structural assembly upon which fabrication operations are to be performed. The bushed spring loaded wedgelock (20) comprises a standard, commercially-available wedgelock modified by attaching a bushing (28) within which a spring loaded spacer (32) is telescopically mounted. Like a standard wedgelock, the bushed spring loaded wedgelock is inserted through collinear holes (16,17) in a drill plate or other alignment fixture and a structural assembly to clamp the assembly to the fixture. Even when used with a structural assembly with curved surfaces or thickness variations, the bushed spring loaded wedgelock (20) clamps structural members together by forcing a spring loaded spacer (32) against the front surface of the structural assembly while the shoulders (26) of the wedgelock arms (24) engage the rear surface of the structural assembly. A variety of wedgelock sizes and designs can be constructed to accommodate a range of alignment fixture, tooling hole and structural assembly geometries.

Description: FIELD OF THE INVENTION The present invention relates to a wedgelock for securing aligned structural members to an alignment plate. BACKGROUND OF THE INVENTION The construction and assembly of a wide variety of equipment, including aircraft, ships, ground vehicles, test equipment and other equipment, frequently entails the fabrication of holes and other features in structural members and the installation of fasteners through such holes to assemble structural members. Holes must often be fabricated which extend through two or more layers of structural material, such as through multiple layers in an aircraft skin, or through two or more structural members, such as through an aircraft skin and an underlying stiffening rib. It is often important that such holes and features be located accurately relative to other features and that such holes and features be fabricated precisely so that the structural integrity of the equipment is maintained. It is conventional in the construction and assembly of equipment with many features for complex sets patterns of holes and other features to be fabricated with the aid of a tooling fixture, such as a drill plate. If, for example, multiple identical assemblies must be constructed, such as for multiple wing assemblies on an aircraft production line, a durable, reusable drill plate in which a pattern of holes or features has been formed may be used as a template by which holes and features in each assembly may be fabricated. The use of a tooling fixture such as a drill plate helps to ensure that all holes in the assembly are precisely located relative to one another. The location of the hole pattern on the structure relative to other features of the structure (i.e. the "float" of the hole pattern over the structure) can be controlled by providing tooling points on the structure which mate to drill plate tooling points and which fix the location of the hole pattern relative to the remainder of the structure. When holes must be fabricated which extend through two or more layers of structural material, such as through multiple layers in an aircraft skin, or through two or more structural members, such as through an aircraft skin and an underlying stiffening rib, there is often a tendency for the layers or members to separate slightly during fabrication operations. For example, when holes through multiple layers are fabricated with a drill, the forward pressure exerted by the drill operator on the assembly tends to force the layers apart as the drill passes through successive layers. When layers separate during fabrication, burrs and chips developed from the structural material by the fabrication tool may lodge between layers. Interlayer burrs and chips may prevent proper fastener attachment or pose other structural integrity problems. The problem of separation of layers or members during fabrication is conventionally addressed by the use of wedgelocks, such as Monogram Aerospace Fasteners Tool Number TD391N1-X. Wedgelocks clamp the tooling plate firmly against the multiple layers or structural members by providing two or more flexible arms which are inserted through collinear holes in the tooling plate and the structural assembly and which engage the back side of the structural assembly by way of a shoulder at the tip of each arm. The opposing end of the wedgelock arms screws into a wedgelock head on the front side of the tooling plate, enabling an operator to adjust the clamping force of the wedgelock by twisting the wedgelock head. Wedgelocks are typically spaced every several inches across a tooling plate to evenly clamp the structural assembly to the tooling plate. Conventional wedgelocks solve to some extent the problem of the separation of layers or members during the fabrication of holes to be drilled through flat surfaces and structural layers or members of uniform thickness, but curved surfaces and varying thicknesses present fabrication difficulties which conventional wedgelocks are unable to adequately overcome. In particular, conventional wedgelocks apply force to the back side of the structural assembly to pull the assembly toward the tooling plate, but the presence of curved surfaces and thickness variations will result in contact between the back side of the tooling plate and the front side of the structural assembly at only a few points. In those areas where the structural assembly is not drawn forcibly against the tooling plate by the conventional wedgelock, drilling or other fabrication operations may cause separation of layers or members, may introduce burrs or chips between layers, and may therefore result in irregular holes and fastener installation problems. The separation of layers results because the conventional wedgelock provides no force to clamp the layers or members together in those areas where the structural assembly is not drawn forcibly against the tooling plate because of surface curvature or thickness variations. The introduction of burrs or chips between layers or members may be a significant problem during construction and assembly operations. If buns and chips are not removed, there may be movement between structural parts during fastener installation. Burr and chip removal may entail expensive and time-consuming disassembly of structural assemblies. Moreover, the diameter of the arms of a conventional wedgelock is often considerably smaller than diameter of the wedgelock alignment hole in the tooling plate to be clamped to the structural assembly, and misalignment may therefore result. There is thus a need for a tool which enables more precise alignment of tooling plates having larger wedgelock alignment hole diameters. While conventional wedgelocks may adequately clamp a tooling plate to a flat and uniform multi-layer or multi-element assembly during fabrication operations requiring moderate hole location accuracy, there is a need for a tool which can enable more accurate tooling plate alignment and which can prevent separation of layers and elements in structural assemblies with curved surfaces and varying thicknesses during fabrication operations. A temporary fastener for clamping multiple layers, such as multilayer composite laminate, is described by U.S. Patent No. 5,240,361 to Thomas E. Armstrong, et al. The fastener includes a force limiting cartridge having a housing and an end cap which screw together to contain a slidable piston biased by a coil spring. The cartridge surrounds a conventional pull-up clamp. The bottom end of the cartridge pushes against the top layer of the laminate. The piston is pushed against the spring when the clamp screw is tightened. The piston is provided with a cross mark which when aligned with cross hairs on the housing indicate a desired clamping pressure has been attained. The cartridge can be calibrated to a desired pressure by adjusting the total length of the housing/end cap assembly. SUMMARY OF THE INVENTION It is thereafter an object of the present invention to provide a wedgelock for precisely positioning and securing a plurality of aligned structural members to an alignment plate by extending through respective apertures defined by the alignment plate and the plurality of aligned structural members. It is a further object of the invention to provide a wedgelock for securing a plurality of aligned structural members to an alignment plate by extending through respective apertures defined by the alignment plate and the plurality of aligned structural members such that the structural members are clamped together during subsequent machining operations. These and other objects are provided, according to the present invention, by a wedgelock comprising the features of claim 1. In operation, an operator uses a tooling plate to accurately and repeatably guide a drill or other fabrication tool to and into a structural assembly workpiece so as to repeatably and accurately fabricate holes or other features in the structural assembly. The wedgelock is inserted through a tooling hole in the tooling plate and thence through a collinear hole in the structural assembly, which may comprise multiple layers or multiple members. Several other wedgelocks distributed relatively evenly over the tooling plate are inserted by the operator through similar sets of collinear holes through the tooling plate and the structural assembly to accurately fix the location of the tooling plate relative to the surface of the structural assembly. Shoulders extending outwardly from the arms of the wedgelock engage the back side of the structural assembly when the operator twists the head of the wedgelock to screw the arms toward the head. The operator can adjust the force with which the tooling plate is held against the structural assembly by the amount of torque applied to the head by hand or with a wrench. After all of the wedgelocks on the tooling plate have been so engaged and the tooling plate is firmly engaged with and accurately located relative to the structural assembly, the operator may commence drilling or other hole or feature fabrication operations on the structural assembly, using the tooling plate as a fabrication tool guide. The bushed wedgelock provided by the present invention permits more precise alignment of the tooling plate to the structural assembly by providing a bushing with a diameter substantially equal to but less than the diameter of the tooling hole in the tooling plate. When multi-layer structural assemblies with curved surfaces or varying thicknesses must be drilled or otherwise fabricated, the spring loaded spacer in the wedgelock of the present invention forcibly engages the structural assembly in regions in which the tooling plate is not in direct contact with the structural assembly, preventing separation of the structural layers or members and thus preventing the generation of excessive burrs or chips between structural layers or members which would be generated in the absence of any clamping force. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the use of a wedgelock for holding a tooling plate to a structural assembly comprising multiple layers. Figure 2 is a perspective view of a bushed wedgelock. Figure 3 depicts a partial cross-section of a bushed wedgelock. Figure 4 is a perspective view of a spring loaded bushed wedgelock. Figure 5 depicts a partial cross-section of a spring loaded bushed wedgelock. Figures 6A, 6B and 6C illustrate the use of a spring loaded bushed wedgelock to clamp multiple layers of a structural assembly together while securing a tooling plate to the structural assembly. Figure 6A depicts the spring loaded bushed wedgelock, the tooling plate and the multi-layer structural assembly before insertion of the wedgelock. Figure 6B depicts the spring loaded bushed wedgelock inserted through the tooling plate and the multi-layer structural assembly, with the shoulders of the outwardly extending arms of the wedgelock engaging the back side of the structural assembly and the multiple layers of the structural assembly clamped together by the force of the compressed spring in the spring loaded bushed wedgelock. Figure 6C depicts the structural assembly secured to the tooling plate after an operator has twisted the head of the wedgelock to screw the arms toward the head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the invention is shown. Like numbers refer to like elements throughout. Structural assembly 10 in aircraft and other equipment may comprise multiple structural elements 11 which are typically constructed of metal, ceramic or graphite/epoxy laminate materials. Holes or other features in structural assembly 10 may be repeatably and precisely fabricated with the aid of an alignment plate 12 which defines template holes 14 through which a drill or other fabrication tool may be guided. Alignment plate 12 is typically constructed of a durable material and may be re-used to repeatably fabricate a common hole pattern through a plurality of structural assemblies 10, such as on an aircraft production line. In order to repeatably and precisely fabricate holes or other features, alignment plate 12 must be clamped or otherwise held securely to structural assembly 10. This clamping or securing function is typically performed by one or more wedgelocks, such as Monogram Aerospace Fasteners Tool Number TD391N1-X. Arms 24 of wedgelock 20 are inserted through alignment plate tooling holes 16, which are collinear with respective structural member tooling holes 17. Shoulders 26 at the end of arms 24 engage the rear surface of structural assembly 10, and arms 24, which are rotatably engaged with head 22 of wedgelock 20, are drawn to head 22 by an operator twisting head 22 with a wrench or by hand until alignment plate 12 is clamped or otherwise held securely to structural assembly 10. Other wedgelocks 20 are spaced evenly across the surface of alignment plate 12 to forcibly clamp structural assembly 10 to alignment plate 12. Hole drilling or other fabrication operations are then performed on structural assembly 10 through alignment plate 12. Alignment plate 12 is typically re-used to fabricate substantially identical sets of holes or other features on additional structural assemblies 10 in a production or assembly line environment, such as on an aircraft assembly line. In one embodiment, shown in Figs. 2 and 3, bushed wedgelock 20 includes bushing 28 which has a bushing flange 30 for contacting the front side of alignment plate 12 and a sleeve portion 34 with length no greater than the thickness of alignment plate 12 and with diameter substantially equal to but less than the diameter of alignment plate tooling hole 16. After arms 24 are inserted through alignment plate tooling holes 16 and respective structural member tooling holes 17, shoulders 26 at the end of arms 24 engage the rear surface of structural assembly 10. An operator draws arms 24 to head 22 by twisting head 22 until bushing flange 30 is held securely to structural assembly 10 and alignment plate 12 is held securely to structural assembly 10. Because the length and diameter of sleeve portion 34 are chosen with knowledge of the dimensions of alignment plate tooling hole 16, alignment plate 12 is precisely located relative to structural member 11. In the preferred embodiment, shown in Figs. 4 and 5, spring loaded bushed wedgelock 20 includes bushing 28, spacer 32 and compressed spring 36. Bushing 28 has a bushing flange 30 for contacting the front side of alignment plate 12 and a sleeve portion 34 with length no greater than the thickness of alignment plate 12 and with diameter substantially equal to but less than the diameter of alignment plate tooling hole 16. Spacer 32 has a diameter substantially equal to but less than the diameter of alignment plate tooling hole 16 and greater than the diameter of structural member tooling hole 17. Spacer 32 is preferably telescopically mounted within and retained by bushing 28 by an inwardly-extending lip on bushing 28 engaging an outwardly-extending lip on spacer 32. Figures 6A, 6B and 6C illustrate the operation of the spring loaded bushed wedgelock. After arms 24 are inserted through alignment plate tooling holes 16 and respective structural member tooling holes 17, shoulders 26 at the end of arms 24 engage the rear surface of structural assembly 10 and compressed spring 36 forces spacer 32 against the front side of structural assembly 10. Structural members 11 are clamped together by opposing forces from spacer 32 and shoulders 26. An operator draws arms 24 to head 22 by twisting head 22 until bushing flange 30 is held securely to structural assembly 10 and alignment plate 12 is held securely to structural assembly 10. Structural members 11 remain clamped together by opposing forces from shoulders 26 and spacer 32, even for structural assemblies with curved surfaces or varying thicknesses, preventing the separation of structural members 11 during drilling or other fabrication operations and precluding the formation of burrs and delaminations which might result from such separation. Bushed spring loaded wedgelock 20 is preferably assembled by inserting spacer 32 and spring 36 into bushing 28 and then press fitting bushing 28 onto a standard wedgelock, such as Monogram Aerospace Fasteners Tool Number TD391N1-X. Bushed wedgelocks and bushed spring loaded wedgelocks for a variety of tooling plate thicknesses and alignment plate tooling hole diameters may be constructed from a range of standard, commercially-available wedgelocks by appropriate choice of bushing and spacer dimensions.

Claims: A wedgelock (20) for securing a plurality of aligned structural members (11) to an alignment plate (12) by extending through respective apertures (16, 17) defined by the alignment plate (12) and the plurality of aligned structural members (11), the wedgelock (20) comprising a head portion (22) and an engagement member extending outwardly from said head portion (22) through the respective apertures (16, 17) defined by the alignment plate (12) and the plurality of aligned structural members (11) and engaging a rear surface of the aligned structural members (11), and characterized in that the wedgelock (20) further comprises: a bushing (28) for extending at least partially through the aperture (16) defined by the alignment plate (12), said bushing (28) being operably connected to said head portion (22) and at least partially surrounding a medial portion of said engagement member; a spacer (32) having a first end disposed within said bushing (28) and a second end for contacting a front surface of the aligned structural members (11); and means for biasing said spacer (32) into contact with the front surface of the aligned structural members (11) such that the structural members (11) are clamped together during subsequent machining operations. A wedgelock (20) according to Claim 1 wherein said means for biasing said spacer (32) comprises a spring (36) in compression disposed within said bushing (28) in operable contact with the first end of said spacer (32) for urging said spacer (32) into contact with the first surface of the aligned structural members (11). A wedgelock (20) according to Claim 1 wherein said spacer (32) is mounted for telescopic movement relative to said bushing (28). A wedgelock (20) according to Claim 3 wherein said bushing (28) and said spacer (32) cooperate to retain at least a first end of said spacer (32) within said bushing (28). A wedgelock (20) according to Claim 1 wherein the aperture (16) defined by said alignment plate (12) has a first predetermined diameter and the apertures (17) defined by the plurality of aligned structural members (11) have a second predetermined diameter, and wherein said spacer (32) has a diameter that is less than the first predetermined diameter of the aperture (16) defined by said alignment plate (12) and greater than the second predetermined diameter of the apertures (17) defined by said plurality of aligned structural members (11). A wedgelock (20) according to Claim 1 wherein said bushing (28) comprises a flange (30) for contacting a front surface of the alignment plate (12) and a sleeve portion (34) for extending within the aperture (16) defined by the alignment plate (12). A wedgelock (20) according to Claim 1 wherein the alignment plate (12) has a predetermined thickness and defines an aperture (16) having a predetermined diameter, and wherein the sleeve portion (34) of said bushing (28) has a length no greater than the predetermined thickness of the alignment plate (12) and a diameter substantially equal to the predetermined diameter of the aperture (16) of the alignment plate (12). A wedgelock (20) according to Claim 1 wherein said head portion (22) is rotatable. A wedgelock (20) according to Claim 8 wherein said engagement member comprises pair of arms (24) for extending through the respective apertures (16, 17) defined by the alignment plate (12) and the plurality of aligned structural members (11), each arm (24) having opposed first and second ends wherein the first end rotatably engages said head portion (22) and wherein the second end includes an outwardly extending shoulder (26) for engaging the rear surface of the aligned structural members (11).

Inventors: BECKER ROBERT O, BLANKENSHIP THOMAS O, MORRISON JAMES L, BECKER, ROBERT O., BLANKENSHIP, THOMAS O., MORRISON, JAMES L.
Applicants: MC DONNELL DOUGLAS CORP, MCDONNELL DOUGLAS CORPORATION
Application year: 1999
Main classification: F16B19
IPC codes: F16B19