Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
2001-10-04
2003-06-03
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
Reexamination Certificate
active
06572006
ABSTRACT:
CROSS-REFERENCES
The present application is related to the subject matter disclosed in U.S. patent application Ser. No. 09/187,511 filed on Nov. 6, 1998 now U.S. Pat. No. 6,244,495 filed on the same date as the patent application, entitled “Gripper”, as well as the subject matter disclosed in U.S. patent application Ser. No. 09/187,083 filed on Nov. 6, 1998 now abandoned also filed on the same date as the patent application, entitled “Indexing Turret.” Both of these applications are incorporated herein by reference in their entirety.
1. Technical Field
This invention relates to friction welders, and more particularly to servo hydraulically driven friction welders.
Although the invention was developed in the field of aircraft engines it has application to other fields where friction welding may be used to accurately and effectively bond two elements together.
2. Background of the Invention
Friction welding is a well-known process in which two components, moving relative to each other, are brought into contact under pressure and bonded at their interface. The motion at the weld interface may be rotational or non-rotational. Non-rotational motion includes linear, elliptical or vibratory motion. Friction welding by rotational motion typically requires at least one of the components be circular in cross section. However, friction welding by non-rotational motion has received attention as a means of bonding components, where the weld interface of both parts is non-circular.
In non-rotational friction welding, one component is oscillated relative to the other component while a forge force is applied normal to the direction of motion. The forge force moves the components into contact, and with metal components the friction between the components generates heat and plasticizes them. Once the motion stops, the metal solidifies, thus bonding the components. This relative simplicity of the process, as compared to other welding processes, lends itself to methodologies that permit tight control of the weld process. Rigid process control may eliminate the necessity of post-weld inspection of the components. Weld parameters such as frequency and amplitude of oscillation, axial displacement, and normal force can be precisely monitored and controlled to produce consistent and repeatable welds.
For plastic components, the friction weld process is typically performed at high frequencies and low forge forces. An example of a process for friction welding thermoplastic components is disclosed in U.S. Pat. No. 4,377,428, issued to Toth and entitled “Method of Friction Welding”.
However, for metal components, the conditions required for friction welding are much more stringent. In addition, there are large forces associated with friction welding metal components. Typically, for metal components the oscillation frequencies are less than/about 100 Hz, depending on the part size and shape, and the forge forces are greater than 5000 lbs. force. A welder having substantial structure is needed to withstand the larger forces associated with friction welding of metal components. Due to the size of such structures, interference between the oscillation frequency and the resonant frequency of the welder is a concern. In addition, repeatability of the process is necessary for process control. Repeatability requires the final position of the components, when welded, to be accurate and predictable.
The actuation system used to generate the oscillating motion must be able to provide a consistent frequency and amplitude and be able to locate the oscillated component in the proper position for forging. One type of actuation system is a mechanically driven system such as that disclosed in U.S. Pat. No. 5,148,957, issued to Searle and entitled “Friction Welding”. In this type of actuation system, cams and joints are used to provide the reciprocating motion. A drawback to mechanically driven actuation systems is the wear, which occurs in the system components. As the system is used, the cams, joints, and bearings will wear which will result in deviations that have to be accounted for, to ensure accuracy and repeatability of the process. Eventually the wear will require replacement of worn parts, which introduces an additional deviation to be accounted for. The actuation system will require re-calibration frequently to account for all the deviations. Another example of a mechanically driven actuation system is disclosed in U.S. Pat. No. 4,858,815, issued to Roberts et al and entitled “Friction Welder Mechanism”.
Another type of actuation system is a servo-hydraulically controlled actuation system, such as that disclosed in U.S. Pat. No. 4,844,320, issued to Stokes et al and entitled “Control System and Method for Vibration Welding”. One limitation to known types of servo-hydraulics is the interference between the oscillating frequency and the natural frequency of the hydraulic column. To generate low frequencies (<100 Hz) and the forge forces needed to move metal components subject to a normal force, the hydraulic columns needed are typically large enough to have natural frequencies of the same order of magnitude as the oscillating frequency.
A particularly useful application for which friction welding is useful is in fabricating integrally bladed rotors for gas turbine engines. An example of this type of application is disclosed in U.S. Pat. No. 5,035,411, issued to Daines et al and entitled “Friction Bonding Apparatus”. An integrally bladed rotor is a rotor assembly wherein the rotor blades are bonded, typically by welding, directly to the rotor disk at spaced intervals about the circumference of the disk. Since there are numerous rotor blades bonded to each disk, the bonding process must be accurately repeatable. In this way individually manufactured components each with selected properties may be joined. Each bonded blade must be accurately positioned within tight tolerances required for aerospace applications. An improved friction welder and method are sought for friction welding large scale, complex shapes formed from various metallic materials.
DISCLOSURE OF THE INVENTION
The present invention is predicated in part upon the recognition that non-planar forces, relative to the plane of the forge pressure, cause deviations in the location of the parts being bonded. The deviation degrades the accurate repeatability of the welding process.
According to the present invention, a friction welder for joining a pair of elements includes a forge assembly having a table defining a platform for disposing one of the elements thereon and wherein, during the application of forge pressure between the elements, non-planar forces in the platform are minimized. Forge pressure is generated between the elements by a forge link disposed on one side of the platform and reacted by a reaction link disposed on the opposite side of the platform. The two links are equidistant from the plane of the platform and connected by a crank that is also pivotally connected to the table.
A principle feature of the present invention is the table having a reaction link disposed opposite of the forge link. The advantage produced thereby is the accuracy of the welded position between the two elements as a result of the minimized non-planar forces in the platform. Minimizing or eliminating non-planar forces in the platform results in minimizing or eliminating deflections and deviations in the relative positions of the elements being welded. Another advantage is the accurate repeatability of the process as a result of the control over deflections and deviations in relative position.
According to another embodiment of the present invention, a method of friction welding a pair of elements includes the step of balancing the moments in the table such that non-planar forces in the platform are minimized. In a specific embodiment, the method includes the steps of placing the forge link in a bent position such that the elements may be positioned in the welder and placing the forge link in the forge position such that forge force may be applied to the elements. Th
Caruolo Antonio B.
Diebold Thomas P.
Yopak Francis J.
Dunn Tom
Johnson Jonathan
Swiatocha John
United Technologies Corporation
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