Turning – Portable lathe for pipe turning
Reexamination Certificate
2003-05-29
2004-06-29
Fridie, Jr., Willmon (Department: 3722)
Turning
Portable lathe for pipe turning
C082S046000, C408S079000
Reexamination Certificate
active
06755101
ABSTRACT:
FIELD AND BACKGROUND OF INVENTION
The present invention relates to beveling tools used to machine a bevel, for example to prepare the ends of tubes or pipes for subsequent welding operations.
Tubes in heat exchangers and reactors, such as the reactor feeders of CANDU power plants, are often arranged in a tightly packed array. As these tubes need repair and replacement, a beveling tool is needed for making repairs. In some cases it is preferable to make these repairs in-situ. This requires a tool that is compact and having a low profile, so that it can operate in the confined space of the tube array. Commercially available beveling tools are typically designed to present a low profile in one axis only. They can fit onto a tube or pipe between two adjacent tubes or pipes when all three are in line. They cannot fit into a nest of tubes or pipes, however, due to the drive motor, which typically is mounted on the side of the tool at 90° to the axis of the tube. There have been some attempts to overcome this limitation by mounting the motor on an axis parallel to the beveling axis, but this still leaves the motor on one side of the tool.
U.S. Pat. No. 4,889,454 issued Dec. 26, 1989 to Hillestad et al. describes a portable, hand held, gas operated rotary tool for milling a surface on the end of a cylindrical workpiece. The apparatus taught in this patent operates at an extremely high RPM, being adapted to turn at rotational speeds of 2,500 to 6,000 RPM, and very low torque. However, standard operating parameters recommended by cutting tool manufacturers for machining, for example, a 2.5″ OD low carbon boiler tube with various cutting tools, are as follows:
Type
Rec. Surface Speed (surface
Rec. Rotational Speed
of cutting tool
feet per minute, SFM)
RPM
carbon steel
25
38
high speed steel
50
76
tungsten carbide
250
328
In the above example, even tungsten carbide cutting tools cannot tolerate surface speeds >250 SFM. When cutting tools are operated at higher than recommended speeds, overheating and tool failure quickly follow. Thus if the apparatus of the Hillestad patent was used to machine a 2.5″ OD low carbon boiler tube at the typical rotary speed of 2,500 to 6,000 RPM taught in the '454 patent, the cutting tool would attempt to remove material at a surface speed of 1636 to 3927 SFM (i.e. &pgr;×OD/12×RPM). This is several times greater than the recommended surface speed for even a tungsten carbide cutting tool, which would quickly overheat and fail.
The Hillestad et al. patent further teaches an axial pin to stabilize the milling head. However, in order to make accurate, repeatable pipe bevels, the entire machining tool must be held rigid and stable. This is only possible when the tool is firmly clamped to the tube. The apparatus of the Hillestad et al. patent is thus only capable of producing crude manual weld preps, and could not be used to produce the precise “J” weld preps, known to those skilled in the art, which are required by present day automatic welding machines.
SUMMARY OF INVENTION
The present invention is drawn to a compact, low profile, in-line beveling tool apparatus suitable for use in a confined space. The overall diameter of the beveling apparatus is small, allowing access to the ends of tubes and pipes even within such a confined space. Commercially available beveling tools are not compact enough, and cannot be used for this application and others.
The present invention can be positioned, set-up and used remotely at any distance from the operator. It is therefore especially suited for use in high radiation areas for nuclear repair applications, where it is desirable for the operator to remain several feet away behind lead shielding. Further, the present invention is completely self-contained, and doesn't require an external device or an operator to hold onto it to resist the torque produced from the cutting action.
Accordingly, one aspect of the invention is drawn to a compact beveling tool suitable for use in a confined space, such as within a tube array.
Another aspect of the invention is drawn to a beveling tool which can be operated remotely, without the operator nearby.
Yet another aspect of the invention is drawn to a beveling tool capable of providing the high torque and low RPM required to make practical use of carbide cutting materials.
In one embodiment, the invention comprises apparatus for beveling an end of a workpiece having a longitudinal axis and a workpiece diameter perpendicular to the longitudinal axis. The apparatus includes a rotatable shaft having an axis of rotation that can be aligned with the longitudinal axis of the workpiece. The shaft has a first and second end, with mechanical means connected to the first end of the shaft for inserting a cutting portion of the apparatus into the workpiece. A housing having an outside diameter surrounds the shaft and has a beveling head mounted thereon adjacent the second end of the shaft. Cutter inserts are mounted on the beveling head. A motor and gear reductions means are contained within the housing surrounding the shaft. The gear reduction means is operatively connected to and located between the motor and the beveling head for producing high torque, low RPM rotary motion of the cutter inserts about the longitudinal axis of the workpiece.
In a further embodiment the invention comprises apparatus for beveling an end of a cylindrical workpiece, the workpiece having a longitudinal axis and a workpiece diameter perpendicular to the longitudinal axis. The embodiment includes a rotatable shaft having an axis of rotation that can be aligned with the longitudinal axis of the workpiece, with the shaft having a first and second end. A flexible cable is rotatably connected to a worm spur gear, the worm spur gear being mounted on the shaft adjacent the first end, for inserting the apparatus into the workpiece. A generally cylindrical housing, having an outside diameter approximately equal to the workpiece diameter, surrounds the shaft. The housing has a beveling head mounted thereon adjacent the second end of the shaft. Cutter inserts comprised of carbide material are mounted on the beveling head. A hollow core air motor surrounds the shaft for producing rotary motion of-the cutter inserts when the air motor is connected to a source of compressed air. A double set of planetary gears, contained within the housing surrounding the shaft, are located between and operatively connected with the motor and the beveling head. The gears are adapted to produce high torque, low RPM rotary motion of the cutter inserts about the longitudinal axis of the workpiece.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the present invention, and the operating advantages attained by its use, reference is made to the accompanying drawing and descriptive matter, forming a part of this disclosure, in which a preferred embodiment of the invention is illustrated.
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pate
Babcock & Wilcox Canada Ltd.
Fridie Jr. Willmon
Grant Kathryn W.
Marich Eric
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