Gear cutting – milling – or planing – Broaching – Cutter support or guide
Reexamination Certificate
2001-09-20
2004-06-29
Howell, Daniel W. (Department: 3722)
Gear cutting, milling, or planing
Broaching
Cutter support or guide
C408S054000, C408S189000, C408S224000, C408S233000, C408S713000
Reexamination Certificate
active
06755598
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to the field of boring tools. The present invention has particular applicability to the field of boring heads of the type used in vertical lathes to produce large diameter bores. The invention is especially useful in producing the bore in the stator yoke of a large electric motor, e.g. a 10,000 hp AC induction motor.
An exemplary stator yoke
10
is shown in
FIGS. 1A
,
1
B,
1
C and
1
D, as used in the 1100 Frame 10,000 hp AC motor produced by Siemens Energy & Automation, Inc. of Norwood, Ohio. Such a yoke
10
is about 89.8 inches in length and includes a yoke bore
12
of about 38 inches in diameter, machined along an axis extending the length of the yoke
10
. Further, the yoke
10
is fashioned with a number of structural ribs
14
, preferably six, that support the stator and provide void areas therebetween for cooling ventilation and weight reduction of the assembled motor. In machining, the yoke bore
12
is ground from the surfaces of the ribs
14
. Three-eighths (⅜) to one-half (½) inch of material must be removed and the bore
12
must be held to a tolerance of about 0.001. This presents a problem during the boring process since the ribs
14
essentially define a non-continuous “interrupted” surface to be machined.
FIG. 2
illustrates a typical previous-type vertical lathe
20
used in a typical boring operation for a large diameter yoke bore
12
. A torque is applied to the lathe
20
which transmits a load to a cutting tool
22
of carbide steel, in order to grind the surfaces of the ribs
14
. However, when the cutting tool
22
comes away from the interrupted surface of the ribs
14
, the load is abruptly released. As the cutting tool
22
comes in contact with the next rib
14
, the load is abruptly reapplied. This interrupted operation results in variable torque and resulting wear and tear upon the lathe motor. Also, the load must be limited to avoid overheating the cutting tool
22
, which would reduce tool life and necessitate frequent tool changes, with increased expense and reduced production efficiency. Consequently, the lathe spindle is fed into the work at about 0.0075 inches per revolution, with a spindle rate of about 60 revolutions per minute (RPM), in order to obtain a permissible load on the lathe motor and to minimize wear and tool changes for the cutting tool
22
. At this rate, it takes about three hours to cut the yoke bore
12
. Thus, the boring process is quite time-consuming, contributing significantly to the production time and thus expense of the product.
SUMMARY OF THE INVENTION
In view of the difficulties and drawbacks associated with previous machining tools and processes, there is therefore a need for a machining tool and process that decreases bore time.
There is also a need for a machining tool and process that decreases tool and machine wear.
There is also a need for a machining tool and process that increases production efficiency.
These needs and others are satisfied by the boring head of the present invention in which a plurality of boring tools provide a plurality of simultaneous cuts to a workpiece. A tool holder supports the plurality of boring tools generally perpendicular to a bore axis, so as to increase the rate of a boring operation.
As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative and not restrictive.
REFERENCES:
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patent: 3180187 (1965-04-01), McFerren
patent: 3213716 (1965-10-01), Getts
patent: 4154555 (1979-05-01), Skrentner
patent: 4181458 (1980-01-01), Roturier
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patent: 4571129 (1986-02-01), Strand
patent: 4768904 (1988-09-01), Schmid
patent: 4948305 (1990-08-01), Reiterman
patent: 4975002 (1990-12-01), Kress et al.
patent: 4995766 (1991-02-01), Coleman
patent: 5018411 (1991-05-01), La Padura
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Tool and Manufacturing Engineers Handbook, Fourth Edition, vol. 1, Machining, Thomas J. Drozda and Charles Wick, Society of Manufacturing Engineers, 1983, Chapter 3, pp. 25, and Chapter 9 pp. 98 and 99.
Rowland James E.
Stepan Vladimir
Howell Daniel W.
Siemens Energy & Automation Inc.
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