Cutlery – Pipe and rod cutters – Rotary
Reexamination Certificate
2000-07-26
2002-06-11
Watts, Douglas D. (Department: 3724)
Cutlery
Pipe and rod cutters
Rotary
C030S101000
Reexamination Certificate
active
06401340
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a tubing cutter. More specifically, this invention relates to a cutter for thin wall tubing such as electrical metallic tubing.
Tubing cutters have been used extensively for many years for cutting metal or plastic tubing and piping for various uses. Such tubing cutters typically have a cutter blade or cutter wheel disposed opposite a pair of rollers. The device is rotated around the tubing in order to cut through the tubing around a circumference thereof. Such devices include means for advancing the blade or wheel into the tubing as the device is rotated around the tubing.
However, under existing building codes, such tubing cutters cannot be used for cutting electrical metallic tubing (“EMT”). EMT must be cut using a hacksaw, which is more laborious. The reason behind the building code ban of such tubing cutters for cutting EMT is that EMT has a thin wall, about {fraction (1/32)} inch in thickness, and conventional tubing cutters compresses the tubing during cutting, thereby reducing its internal diameter. If wiring is pulled through such reduced diameter EMT, the extra resistance caused by the reduced diameter of the EMT can cause the wiring's diameter to be reduced thereby creating less amperage carrying capacity.
In addition, conventional tubing cutters leave a rough inside burr which can skin insulation from the wiring as it is pulled through the EMT.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a rotary tubing cutter for thin wall conduit that does not reduce the internal diameter of the conduit during cutting.
It is another object to provide a rotary tubing cutter for thin wall conduit which leaves a minimal internal burr which can be easily removed with a reamer.
These and other objects are accomplished by providing a depth gage stop means associated with the cutting member of the tubing cutter which prevents the cutting member from cutting entirely through the wall of the EMT. After the wall of the EMT is partially cut through, preferably about 50% of the way through, the tubing cutter is removed from the EMT, and the EMT manually broken in two at the partial cut.
REFERENCES:
patent: 73528 (1868-01-01), Hartford
patent: 134477 (1872-12-01), Jepson
patent: 171789 (1876-01-01), Franke
patent: 2739381 (1956-03-01), Petersen
patent: 3013335 (1961-12-01), Kowal
patent: 3171199 (1965-03-01), Meese
patent: 5414932 (1995-05-01), Azkona
patent: 5515609 (1996-05-01), Sperti
patent: 5765289 (1998-06-01), Schulz et al.
patent: 5907906 (1999-06-01), Sweeney
Howard Robert E.
Watts Douglas D.
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