Electric heating – Metal heating – Rail bond
Reexamination Certificate
2000-02-28
2001-08-21
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
Rail bond
C219S124340, C219S125100, C901S042000
Reexamination Certificate
active
06278074
ABSTRACT:
The present invention relates to a method and system for welding the spaced ends of rails and more particularly to welding two spaced railroad rails by using an electric arc welding process.
BACKGROUND OF INVENTION
The narrow gap between facing end walls adjacent first and second railway rails must be filled accurately and rapidly with molten metal if an electric arc welding process is to be successfully used in the field. To accomplish this objective, technology has advanced to the concept of moving the electric arc welding torch back and forth in the gap by a robotic mechanism. In the past, the movement of an electric arc welding torch is controlled by a robotic mechanism by use of an executive software program using somewhat low level language. The program is created by moving the torch in the desired path and recording this movement in program language so that the movement can be duplicated when the next rail joint is being filled. The creation of a computer software program for controlling the movement of a robotic mechanism has resulted in somewhat unsuccessful welding procedures that demands a substantial amount of operator attention. When an executive program is generated by moving a torch in the gap and periodically storing the movement by a software program, difficulty has been experienced when using the program in the field to weld a joint. The narrow gap between the rails is not uniform from one joint to the next and is not ideal for any joint. The gap is formed in the field by a rotary cutting wheel slicing off the end of one rail and then the end of another rail. These rails are then positioned to define the gap. These roughly cut rails are positioned by less than a precise procedure. The two end surfaces are not necessarily parallel. The program heretofore used for moving the arc welding torch for filling the gap has been fixed and based upon ideal positioning of the end walls and a precise spacing of these walls. Consequently, robotic control and automatic welding of the gap between spaced rails in the field has not been universally successful from one gap to the next. The limitation in the past has been the use of a computer software program which is based upon ideal movements of the torch in an ideal, but imaginary, gap. Hopefully the ideal gap is close to the actual gap being filled during the arc welding process. An unsuccessful filling operation results in a rejected joint. In the field often such rejection involves rerouting trains to avoid the work area where the joint is being filled. This is unacceptable and somewhat mitigates against successful implementation of a computer controlled robotic mechanism for filling the joint between spaced rails. The spacing of the end wall is not always the same; consequently, use of an ideal torch movement is not always successful in providing a satisfactory weld joint.
THE INVENTION
The present invention relates to the development of a programming concept wherein a low level language or software program, normally associated with robotic movement controls, is used in parallel with a background, high level language, such as KAREL, by using a unique method for controlling the movement of the electric arc welding torch. The invention involves the creation of a fixed data file, or text file, which involves a series of positions defining the total welding process for filling the gap between the rails. This text file or data array is like a spreadsheet wherein a series of positions are fixedly set in the data array in a manner that each position is defined by a set of coordinates that specifically indicate the position in which the torch is located for the welding process. Each fixed position information includes the welding parameters, such as voltage, travel speed or delay at end of movement associated with a position. The parameters are executed as the torch moves in a preselected path toward a known next position. When the path has been completed and the torch is ready to execute such next position, information relating to the next position is outputted and processed so that a series of individual positions are processed to constitute the total filling procedure by the electric arc welding torch. Each position recorded in the spreadsheet format of the data array is assigned to a specific vertical layer of deposited metal for the welding process. A number of positions are executed in series to produce a layer of fill metal. At the end of the implementation of one welding cycle corresponding to a specific position, the high level background software program senses and determines the vertical height, or z coordinate, of the welding process. If this sensed z coordinate does not correspond to the next position to be cycled from the spreadsheet, the z coordinate of the next position being processed is modified. Indeed, stored z coordinate is replaced with the sensed z coordinate. In the welding process, successive layers are deposited. Some of these layers are to be repeated, if not fully filled. If the position being processed is at the end of a specific layer of molten metal which must be filled, the z coordinate or height of the electric arc welding torch is compared with a known height for the specific layer. When the layer has been completed, the next layer is processed. If the layer is not completed, the positions making up the short layer are repeated. Consequently, a fixed series of welding steps assigned to a metal layer are processed seriatim and, then the vertical height of the welding torch is measured to determine whether the next layer is to be processed. The procedure of outputting a series of fixed stored welding steps identified by the specific orientation of the torch and the layer being processed has proven to be successful. Adjustments are made based upon the actual height of the torch after certain welding steps. Consequently, an aspect of the invention is the use of a spreadsheet type fixed data array or text file, which file has data that can be outputted as one position then another position, each position constituting the orientation of the torch and the particular layer being filled as the torch moves. The implementation of each welding step as individual positions, uses a low level robotic executive software program. At the same time a high level program is used to sense the vertical position of the torch for creating digital information indicative of the actual vertical height of the torch. The height, or z coordinate, can be used to modify the position of the torch at the start of a given welding step.
The data array is created for welding an ideal gap, which gap geometry is not found in the field. Consequently, in accordance with another aspect of the invention, the high level computer program software language is used to create “user frames” that are reference planes indicative of the actual end walls of the spaced rails being welded. The reference planes form the narrow gap to be filled. In accordance with this aspect of the invention, a stylus or other known mechanical device carried by the torch is moved to selected points on one of the end walls. The relationship between the home position of the robot and the selected first point is read and recorded as x, y and z coordinates of the first point. Thereafter, the x axis is measured by moving the stylus to a second point. The x, y plane is determined by selecting a third point by the stylus. The three spaced points on the surface of the end wall define a reference plane that is calculated by the background software program. This reference plane is a “user frame” representing the actual plane of the end wall surface. This same procedure is performed on the other end wall so that a user frame, or reference plane, is calculated for each of the two end walls. These end walls may not be parallel, either vertically or horizontally. By calculating the reference planes of the actual end walls, the actual gap is defined. A plane in the middle of the two reference planes is calculated by the background program. This middle user frame is equidistance fro
Morlock Michael J.
Mumaw James W.
Lincoln Global Inc.
Shaw Clifford C.
Vickers Daniels & Young
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