Metal working – Means to assemble or disassemble – With signal – scale – illuminator – or optical viewer
Reexamination Certificate
2000-04-12
2003-02-04
Vidovich, Gregory M. (Department: 3726)
Metal working
Means to assemble or disassemble
With signal, scale, illuminator, or optical viewer
C029S281500, C029S056600
Reexamination Certificate
active
06513231
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to assembly-line systems for assembling a plurality of identical structures, and more particularly to the assembly of large mechanical structures such as aircraft wing boxes that are cumbersome to move from one assembly station to another.
BACKGROUND OF THE INVENTION
Henry Ford is generally regarded as the father of modern mass production. Ford recognized that great strides in efficiency of mass production could be realized by standardizing the design of an automobile so that parts could be interchangeably used from one automobile to another, and by dividing the assembly of an automobile into a number of different tasks. Ford also conceived that workers could perform more efficiently if each repetitively performed the same task or set of tasks on each automobile. Efficiency in the flow of products was improved by stationing workers at fixed workstations arranged along an “assembly line” and by moving each automobile along the line from one workstation to the next. Each workstation had the parts and equipment that its workers would need to perform their assigned tasks. Since Ford's pioneering work, it has become standard across virtually all industries to use moving assembly lines in the mass production of products.
Improvements in manufacturing efficiency and cost have also been achieved by improving the control of parts inventories and flow. One example is the advent of “just-in-time” inventory systems in which parts are replenished in the inventory at the rate they are used, so that a large inventory is not needed. The “kanban” (a Japanese term meaning “replenishment to order”) inventory system is one version of this, in which the usage of each part is communicated from the user to the part supplier as the parts are used, and the supplier delivers parts of the same type and number as are used. In most cases, the delivered parts are received at a loading dock and are then transported from the loading dock to a central parts storage area where all parts used in the manufacture of the particular product are stored and catalogued. Alternatively, the parts can be transported from the loading dock to one or more parts storage areas proximate the point of use.
Moving assembly lines can be difficult to implement when the product is so large or delicate that it cannot be practically moved from one workstation to another. For instance, aircraft wing boxes for large commercial aircraft can be quite large and heavy. Accordingly, wing boxes have traditionally been assembled by keeping the wing boxes in fixed locations. Where the wing boxes are assembled in vertical orientations, custom-built worker platforms are positioned in proximity to a wing box so that workers can access all portions of the wing box. Teams of workers successively perform their assigned tasks on the wing boxes until they are completed. In the process, tools and equipment needed for a given set of tasks are retrieved by the workers from racks stationed on the assembly floor, carried to the wing box being assembled, and used for performing the tasks. Component parts to be installed in a wing box are generally stored in a number of parts storage racks located in the assembly building. Workers retrieve the parts from the racks and the parts are carried or transported to the wing box. Parts are replenished in the racks by transporting them from a part-receiving area (i.e., a loading dock) to the racks and placing them in their proper locations so that they can be subsequently retrieved. In most cases, the parts racks are not immediately adjacent to the wing box being worked on, and hence, workers must travel to the racks to retrieve the needed parts. Likewise, tools are typically not stored immediately adjacent to the wing box location, and thus the workers must travel to the tool storage area to retrieve needed tools.
The assembly method described above has certain drawbacks. One significant disadvantage is the time that is wasted by workers traveling from the assembly location to a tool or parts storage rack, retrieving the needed tools and/or parts, and traveling back to the assembly location. This inefficiency could be substantially reduced by storing the tools and parts at the point of use. In many cases, however, it may be impossible or undesirable to use space on the assembly floor for such purpose; for example, the cost per square foot for an assembly building is often much higher than that for a parts warehouse, such that it may be economically disadvantageous to store parts at the point of use.
A further drawback in the above-described assembly system is that elaborate and expensive positioning and fixturing devices have generally been necessary for precisely positioning and holding component parts in their proper locations so that they can be drilled and fastened to the wing box. For example, in many determinant assembly processes for large structures such as wing boxes, large 5-axis gantry machines are used, sometimes in conjunction with laser tracking devices, for positioning component parts and fastening the parts to the structure. These devices are relatively expensive.
SUMMARY OF THE INVENTION
The above needs are met and other advantages are achieved by the present invention, which provides a system and method for the assembly of large mechanical structures that cannot practically be moved from one workstation to another. In accordance with the principles of the present invention, the mechanical structures to be assembled are fixed in stationary assembly jigs spaced apart on an assembly floor. A plurality of different, specialized work operations are performed on each structure by successively moving a plurality of mobile workstations to the structure. Each workstation is designed to facilitate a particular set of work operations. In one embodiment of the invention for use in assembling aircraft wing boxes, the workstations can include a drilling and fastening workstation, a systems installation workstation, a functional test workstation, and a self-contained cleaning workstation. Each workstation comprises a mobile module that can travel along the assembly floor from one assembly jig to the next. One or more of the workstations include a worker platform facilitating worker access to the structure being assembled.
Advantageously, at least one of the workstations includes a parts storage module for storing component parts to be installed in the mechanical structures. The required tools for the assembly tasks can also be stored in the parts storage module. Thus, the parts and tools needed for performing a given set of tasks are located immediately adjacent the point of use, thereby substantially reducing the time required for retrieving parts and tools. Preferably, the parts storage module(s) can be moved to a part-receiving area (e.g., a loading dock) for directly receiving parts when they are delivered by the supplier, thereby eliminating central inventory storage. The parts storage module(s) can interface with the worker platform(s) so that workers on a worker platform can easily retrieve parts or tools from the parts storage module without leaving the platform.
In one embodiment of the invention, one or more of the workstations include docking members and the assembly jigs include cooperating docking members that engage the docking members of the one or more workstations for aligning the workstations with the assembly jigs. This enables the workstations to index to the assembly jigs so that part positioning and fixturing devices mounted on the workstations can accurately position component parts relative to the mechanical structure.
Advantageously, at least one workstation includes one or more indexing devices for positioning components to be installed in the mechanical structure so that the components can be affixed to the mechanical structure. The indexing devices can comprise indexing arms that are mounted on a mobile worker platform. The platform indexes to the assembly jig, preferably by way of the docking members, so that the indexing arm
Frome Cliff G.
Hafenrichter Joseph L.
Lisk David Edgar
Alston & Bird LLP
Hong John C.
The Boeing Company
Vidovich Gregory M.
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