Appeal No. 95-4081
Application 08/071,895
eases cold weather starting and insures that the
hydraulic control system will properly "shift gears".
High viscosity at elevated temperatures insures
pumpability and the satisfactory operation of converters,
valves, clutches, gears and bearings. These conflicting
fluidity requirements require a product that exhibits the
following characteristics:
(a) high temperature viscosity retention,
(b) low temperature fluidity,
(c) shear stability, and
(d) high temperature stability.
In order to prepare lubricants having these
characteristics, it has become common practice to add a
variety of chemicals to the lubricating oil. For
example, in order to meet the viscosity requirements,
compositions have been added to the oils which are
characterized by relatively small change in their
viscosity with changing temperature. In general,
lubricants containing such compositions have the
desirable properties of functioning immediately, even
though cold, upon being put into service, and to continue
to function satisfactorily as they become heated during
operation. Commonly used gear oil viscosity improvers
include polymethacrylates and polyolefins.
In addition to viscosity improvers, lubricating
compositions useful as gear lubricants generally will
contain pour point depressants, extreme pressure agents,
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Last modified: November 3, 2007