Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
1998-10-05
2001-04-17
Pyon, Harold (Department: 1722)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S111000, C164S112000
Reexamination Certificate
active
06216763
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of joining elements in vehicle structures. More specifically, the present invention relates to a method of joining elements by casting around them as they are held in a desired configuration and to a node formed by such a method.
In many instances, it is necessary to create structural members such as frames to provide overall support to component devices. This is particularly true in the manufacture and assembly of vehicles such as automobiles, trucks, sport utility vehicles and the like. Such a vehicle frame is shown in U.S. Pat. No. 5,149,132 entitled SPLIT REAR TRUCK FRAME, which is assigned to the assignee of the present invention and is incorporated herein by reference. Another example of such a truck frame and its related mounting structures can be found in U.S. Pat. No. 5,308,115 entitled VEHICLE FRAME WITH OVERLAPPED SECTIONS, also assigned to the assignee of the present invention and incorporated herein by reference.
A vehicle is assembled, at least in part, by constructing a frame or main assembly and attaching subassemblies and components to the frame. The frame includes two generally parallel, spaced-apart side rail members which run substantially the length of the vehicle. Cross members span the distance between the side rails and are attached at their ends to the side rail members. Vehicle subassemblies and components include the engine cradle, suspension system, body panels, control arms, rear box load, cab, brake and fluid lines, and the like.
The unions or connections between elements are made directly or indirectly. Typically, direct unions are made by welding, bolting, riveting or the like. Indirect unions involve attaching a bracket to one member and then attaching a component to the bracket. Brackets are typically configured to accommodate a single particular component, and are typically attached by bolting, riveting, welding or the like.
Using bolting, riveting, and welding for these joints has a number of disadvantages. For example, one disadvantage with bolting, riveting, or welding involves the “fitting up” of the elements to be joined. That is, for a bolt or rivet to properly join two elements, the two elements must perfectly abut each other, or be fairly precisely parallel to one another. If one element is disposed at an angle to the element to which it is to be joined, the bolt or rivet will not be able to pull the two elements securely together. Therefore, careful orientation of the two elements is required to prepare the two elements for bolting, riveting, or welding.
Another disadvantage with bolting and riveting is that holes must be machined or stamped into the elements to accommodate bolts or rivets. This involves an additional manufacturing step, which increases the time, labor, and cost of the vehicle frame.
Bolting and riveting is further disadvantageous because the holes in the two elements to be joined must precisely match up. Therefore, tolerances for the placement of the holes must be fairly rigorously maintained. This increases the labor and therefore the cost of manufacturing the vehicle frame.
A still further disadvantage of bolting, riveting, and welding, involves the “stack up” of tolerances when multiple elements are joined. The elements must be designed to accommodate each other when mating features of each element, such as size and placement of holes for bolting, are at the extreme edges of their respective tolerance ranges. This is of particular concern when, for example, two elements are joined to one another and then joined to a third element. The third element must accommodate the stacked up tolerances or the sum of the tolerances of the first two elements.
A disadvantage to connecting elements through bracketry is that the brackets or mounting members are extra elements, requiring time and labor to produce and assemble. Further, additional parts require additional time and labor in regulating quality control and in tracking and storing inventory. This increases the cost of the resulting vehicle frame.
In light of the above-described disadvantages, it would be desirable to provide a method of joining or connecting elements that does not rely upon bolting, riveting, or welding. Further, it would be desirable to provide a joining method that eliminates the need for mating surfaces to match or “fit up” and to be precisely positioned for connection. Still further, it would be desirable to provide a connecting method that does not require specific structure, such as holes for bolting or riveting, to be incorporated into the elements to be joined. Further, it would be desirable to provide a method of uniting elements that would eliminate the stack-up of tolerances when multiple elements are joined.
SUMMARY OF THE INVENTION
In light of the above described problems with prior art devices and in keeping with the objectives discussed above, the present invention provides a method of joining or uniting elements in a vehicle structure. In this method, joints or nodes are cast around the elements to be joined. More specifically, the present invention provides a method of joining or uniting elements by positioning the elements and fixing them or holding them in place, and then casting a joint or node around them. Still more specifically, the present invention involves a method of joining elements in a vehicle frame including the steps of fixing elements in a desired orientation; providing complimentary dies which define an interior cavity; positioning the dies about the mating portion of the elements, such that the mating portions extend into the die cavity; introducing material under pressure into the die cavity and filling the die cavity; and removing the dies, leaving a molded joint connecting the elements in a desired orientation, with the molded joint having the shape of the die cavity.
This method may be used to connect a variety of elements that ultimately form a vehicle structure. For example, this method can be used to connect a main member to another main member or to a bracket. Examples of main members include side rail members and cross members which form the vehicle frame. In addition, elements which form subassemblies for the engine cradle and for the rear suspension can be assembled according to this method and can then be connected to the frame using this method. Further, this method can be used to mold brackets or other mounting members into a joint between elements. Still further, this method can be used to attach a contact plate to a member, such that that member can then be bolted or riveted to another member that is made of a material incompatible with the first member. This method can also be used to connect brackets or other mounting surfaces to one another in a matrix formation.
This process of casting a node or joint around elements avoids the need for machining or stamping holes in the elements to accommodate bolts or rivets. Further, mating members are not required to have similarly contoured and nearly perfectly oriented mating surfaces as would be required for bolts, rivets and welds to make a secure connection. The present invention further provides a method of joining elements without the stacking up of tolerances of the elements to be joined. Still further, this method allows the use of steel for large members that must be of high strength, while also allowing the use of lighter materials, such as aluminum, for the relatively small and complexly shaped molded nodes. In this manner, large members can be of relatively cheap material while more expensive materials can be reserved for the comparatively small nodes. Nodes made by the method of the present invention can be molded to spread the stresses of the joint to a greater degree than is allowed by welded, bolted or riveted joints.
It is an object of the present invention to connect elements in a vehicle frame without having to provide holes in the elements to be connected. Such holes must meet strict tolerances, and require an extra manufacturing step of machining or stamping of the hole
Kretschmer Stephen L.
Ruehl Phillip C.
Lervick Craig J.
Lin I.-H.
Oppenheimer Wolff & Donnelly LLP
Pyon Harold
R. J. Tower Corporation
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