Cutting by use of rotating axially moving tool – Processes – Bit detachable
Reexamination Certificate
2000-06-02
2001-10-30
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
Processes
Bit detachable
C082S113000, C408S080000, C408S111000, C408S137000, C409S178000
Reexamination Certificate
active
06309145
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to portable machine tools useful for preparing existing openings in heat exchange header structures for butt-welding new heat exchange tubes thereto.
2. Discussion of Related Art
Prior art techniques are known for machining the ends of pipes and tubular conduits in preparation for welding wherein a portable machine tool is secured to the pipe or conduit by means of a centered mandrel locked within the pipe and supporting the machine tool. The machine tool is advanced along the mandrel to feed a cutter head into engagement with the end of the pipe in order to generate a profile suitable for welding the pipe to another pipe or another structure.
Such a technique also has been used to machine openings in structures to which a tube is to be butt-welded. In a procedure of this kind, a mandrel can be locked within the opening and the machine tool can be advanced into engagement with the surface material surrounding the opening on one side of the structure through which the opening extends. During machining, the machine tool is literally supported by the mandrel which must react the torque and bending loads imposed on the cutting head of the machine tool as well as axial and transverse forces imposed during the machining operation.
Large heat exchange systems, such as boilers, condensers, evaporators, etc. utilize multiple heat exchanger tubes that are in direct engagement with a heating or cooling medium and which contain a fluid medium in heat exchange relationship with the heating and cooling medium. Fluid is supplied and extracted from such tubes through larger conduits or tanks located at upper and lower areas of the heat exchanger and which distribute fluid through the heat exchanger tubes.
Because the heat exchanger tubes are exposed to severe environmental conditions, they must be removed and replaced with some frequency. Typically, a defective tube is cut from the header at a location closely adjacent the tube opening in the header and then a machining operation is performed to completely remove the stub end of the tube from the header while preparing the tube opening for butt-welding a replacement tube to the header.
The thickness of the sidewalls of such headers limits the surface area against which the machine tool mandrel may be anchored when it is desired to use a machine tool maneuverable along a mandrel of the type described above. Because of the instability of the mandrel over its full length, high loads imposed on the mandrel result in transverse bending of the mandrel which produces a poor quality finish of the machined surfaces.
It is highly desirable to stabilize the machine tool in a manner to avoid bending of a mandrel supported in a header opening during machining of the opening in preparation for butt-welding a new heat exchange tube to the opening.
BRIEF SUMMARY OF THE INVENTION
The present invention involves stabilizing the machine tool relative to a header opening by providing circumferentially spaced stabilizing legs engaging the outer surface of the header adjacent the opening and thereby stabilizing the mandrel extending through the opening for supporting the machine tool against motion relative to the header during machining of the opening area.
More specifically, a portable machine tool is provided that includes a longitudinal extending mandrel having a distal end area insertable into an opening of a header or other plate structure having inner and outer wall surfaces intersected by the opening. The mandrel distal end area is adapted to support a radially extending stop member and radially extendable centering blocks that secure the mandrel against withdrawal from the opening and center the mandrel within the opening.
A transversely extending upper plate is slidably mounted on the mandrel and has secured thereto circumferentially spaced stabilizing legs extending parallel to the mandrel towards the surface of the header or plate structure. A lower plate is also mounted on the mandrel and supports a machine tool drive and a cutting head facing the opening in the plate structure to be machined. The mandrel is stabilized against the header or plate structure by pulling upwardly against the mandrel by pressing downwardly against the stabilizing legs to react the mandrel load into the plate structure. The tensioned mandrel and compressed stabilizing legs, which are individually adjustable in length to accommodate any curvature in the header or plate structure, stabilizes the mandrel against transverse or bending loads during operation of the cutting head.
The machine tool may be advanced relative to the mandrel by a feed nut arrangement that may be manipulated by the tool operator. The machine tool drive preferably is mounted on the lower plate which is slidable along the stabilizing legs to enable the cutting head of the machine tool to remove any stub end of a tube previously butt-welded to the opening and to clear the opening area of any residual weldment remaining from the previous tube installation.
The invention will be understood upon consideration of the detailed written description that follows in conjunction with the appended drawings.
REFERENCES:
patent: 4470734 (1984-09-01), Miller
patent: 4498820 (1985-02-01), Brennan
patent: 4533284 (1985-08-01), Agius et al.
patent: 5531550 (1996-07-01), Moruzzi
Tremblay Clement
Vanderpol Jerald
Bacon & Thomas PLLC
Howell Daniel W.
Tri Tool Inc.
LandOfFree
Portable machine tool for conditioning header tube openings... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Portable machine tool for conditioning header tube openings..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Portable machine tool for conditioning header tube openings... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587499