Measuring and testing – Frictional resistance – coefficient or characteristics – Lubricant testing
Reexamination Certificate
2000-07-24
2002-07-16
Raevis, Robert Roers (Department: 2856)
Measuring and testing
Frictional resistance, coefficient or characteristics
Lubricant testing
C073S009000
Reexamination Certificate
active
06418776
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of tribology and, more particularly, to a method and apparatus for testing and measuring friction, wear characteristics of materials, and tribological properties of lubricants.
BACKGROUND OF THE INVENTION
Tribology is a science of friction, wear, and lubrication on friction surfaces. Many different types of friction testers, tribometers, and other devices for measuring various parameters of friction are known. U.S. Pat. No. 5,795,990 issued in 1998 to N. Gitis, et al. describes a friction tester which has a horizontal base with a vertical column that supports vertical guides for guiding a carriage.
FIG. 1
is a fragmental sectional view of the aforementioned tester, which has a lower base
10
, and a vertical column (not shown). A carriage
16
supports a rotary stepper motor (not shown) that rotates an upper specimen holder
64
via a reducer
66
. The upper specimen holder
64
is strictly coaxial with the center of a bowl
22
, which is supported by the lower base
10
via a lower plate
24
. The upper specimen holder
64
has a radial guiding slot, which serves for guiding a slider
68
, the position of which can be adjusted by means of a micrometric screw. The upper specimen holder
64
supports a collet chuck
19
that holds an upper specimen
20
by means of a coupling
76
supported in the upper specimen holder
64
by means of an angular adapter
78
which has a horizontal axle
80
inserted into an opening of the slider
68
.
A sensor, e.g., a load cell
29
, is placed between the lower plate
24
and an intermediate plate
30
for measuring a friction force and friction torque developed during testing between the upper specimen
20
and a lower specimen
21
.
Thus, in the known tester of U.S. Pat. No. 5,795,990, the slider and the collet chuck
19
together with the upper specimen
20
perform orbital movements over the stationary lower specimen
21
. Rotation of these relatively heavy parts develops centrifugal forces which deform, i.e., bends, the rotating chuck
19
with the upper specimen
20
radially outwardly from the vertical axis of rotation. It is impossible to obtain accurate measurements and it is difficult to provide electrical connections with the rotating parts, e.g., if a heater is installed on a rotating part. Furthermore, the orbital rotation of aforementioned heavy parts limits frequency of rotation (which did not exceed 60 rpm in a real tester) and requires the use of the reducer
66
(which was a harmonic drive reducer in a real tester).
Another disadvantage of the known tester is lack of versatility resulting from the upper attachment of the rotating parts. Such an arrangement limits a space for attachment of various replaceable modules, such as modules with heating, reciprocating drives, etc.
In the known tester the sensor
29
is located beneath the bowl
22
and all other fixtures, so that the weight of these devices acts on the sensor and therefore does not allow obtaining accurate measurements.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an apparatus for testing and measuring tribological properties of the materials and lubricants which is simple in construction, reliable in operation, universal in use, allows testing with high frequencies of rotation and under different temperatures, prevents deformations in the friction force measurement system, and therefore ensures accurate measurements. Another object of the invention is to provide a method for testing and measuring tribological properties of the materials and lubricant which is reliable and allows testing in a wide range of operation conditions.
REFERENCES:
patent: 4448083 (1984-05-01), Hayashi
patent: 4939922 (1990-07-01), Smalley et al.
patent: 5795990 (1998-08-01), Gitis et al.
patent: 6167745 (2001-01-01), Hamer et al.
Dorfman Vlad
Gitis Norm
Vinogradov Michael
Center for Tribology, Inc.
Raevis Robert Roers
Zborovsky Ilya
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