Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-11-23
2002-09-10
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S036000, C073S660000
Reexamination Certificate
active
06449564
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to shaft cracking and incipient pinion slip, and more particularly, to monitoring shaft cracking and incipient pinion slip in an operating system such as a geared system of a locomotive.
In a geared system, the motion or torque from one shaft is transmitted to another shaft by means of direct contact between toothed wheels or gears.
FIG. 1
illustrates one example of a geared system
10
for propelling a locomotive. Geared system
10
includes an electric motor
12
having a drive shaft
14
rotatably supported by bearings
16
which are attached to the locomotive, a rotor
11
, a stator
19
with stator windings
21
and leads
23
. Attached to one end of drive shaft
14
is a pinion
18
. Typically, pinion
18
is fitted and shrunk onto a tapered end
15
of drive shaft
14
. Pinion
18
engages a bull gear
20
which attaches to and drives a wheel shaft
22
rotatably supported by bearings
24
. The ends of wheel shaft
22
are attached to respective wheels
26
of the locomotive.
Although electric motor
12
is resiliently supported to the locomotive, geared system
10
experiences large mechanical vibrations, e.g., shock loadings due to uneven portions of rails
30
. Often, after some period of heavy usage, drive shaft
14
may crack due to fatigue. Similarly, pinion
18
may slip relative to drive shaft
14
without any advanced warning so that torque is no longer transmitted to wheels
26
. Such failures can be catastrophic, and repairs such as removal of electric motor
12
, refitting of pinion
18
, or replacement of drive shaft
14
, are expensive, labor intensive, and require that the locomotive be temporarily pulled from service.
Therefore, there is a need for an apparatus and method for low cost, on-line monitoring of an operating geared system in which the apparatus and method are capable of warning of shaft cracking or incipient pinion slip.
SUMMARY OF THE INVENTION
The above-mentioned need is met by the present invention which relates to diagnostic techniques for monitoring shaft cracking or incipient pinion slip in an operating system. In one aspect of the present invention, a method for monitoring shaft cracking or incipient pinion slip in an operating system includes the steps of determining a characteristic natural frequency of the operating system at a first time, determining the characteristic natural frequency at a second time, and comparing the characteristic natural frequency determined at the first time to the characteristic natural frequency determined at the second time to detect a shift in the characteristic natural frequency in response to at least one of shaft cracking and incipient pinion slip.
For monitoring shaft cracking, the characteristic natural frequency is a natural frequency of a shaft of the operating system. For monitoring pinion slip, the characteristic natural frequency is a natural frequency of an assembly including a pinion of the operating system or the characteristic natural frequencies of two coupled assemblies which includes the pinion.
The steps of determining the characteristic natural frequency may include measuring vibrations of the operating system, measuring current of a motor of the operating system, measuring torsional oscillations of the operating system, or measuring current and voltage of a motor of the operating system. Advantageously, the steps of determining the characteristic natural frequency may include the step of performing a fast Fourier transform analysis.
In another aspect of the present invention, an apparatus for monitoring shaft cracking or incipient pinion slip in an operating system, includes a controller adapted to determine a characteristic natural frequency of the operating system at a first time, determine the characteristic natural frequency at a second time, and compare the characteristic natural frequency determined at the first time to the characteristic natural frequency determined at the second time to detect a shift in the characteristic natural frequency in response to at least one of shaft cracking and incipient pinion slip.
In still another aspect of the present invention, an article of manufacture comprises at least one computer usable medium having computer readable program code means embodied therein for causing the monitoring of shaft cracking or incipient pinion slip in an operating system. The computer readable program code means in the article of manufacture comprises computer readable program code means for determining a characteristic natural frequency of the operating system at a first time, determining the characteristic natural frequency at a second time, and comparing the characteristic natural frequency determined at the first time to the characteristic natural frequency determined at the second time to detect a shift in the characteristic natural frequency in response to at least one of shaft cracking and incipient pinion slip.
In yet another aspect of the present invention, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine, performs a method for monitoring shaft cracking or incipient pinion slip in an operating system, as noted above.
REFERENCES:
patent: 4352293 (1982-10-01), Kurihara et al.
patent: 4931949 (1990-06-01), Hernandez et al.
patent: 4975855 (1990-12-01), Miller et al.
patent: 5068800 (1991-11-01), Brook et al.
patent: 5159563 (1992-10-01), Miller et al.
patent: 5365787 (1994-11-01), Hernandez et al.
patent: 5479824 (1996-01-01), Torres
patent: 5533400 (1996-07-01), Gasch et al.
patent: 5895857 (1999-04-01), Robinson et al.
patent: 0178468 (1986-04-01), None
patent: 60195426 (1985-10-01), None
SU 1300322 A (Trashk Rail Trasport) Jan. 30, 1987, (Abstract), Soviet Inventions Illustrated, Section EL: Electrical, Week 8743, PP 11-12, 1987, London, Derwent Publ. LTD. AN 87-305669/43.
SU 817506 A (Tashk Rail Eng) Apr. 5, 1981, (Abstract), Soviet Inventions Illustrated, Section EL: Electrical, Week E02, PP 24-25, 1982, London Derwent Publication LTD., AN A911E/02.
RU 2082143 C1 (Elektrosila Stock) Jun. 20 1997, (Abstract) [online] [retrieved on Dec. 22, 2000] Retrieved from: WPI—Database.
Kliman Gerald Burt
Reddy Suresh Baddam
Sribar Rok
Charioui Mohamed
Hoff Marc S.
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