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Description  |
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FIELD OF THE INVENTION
This invention relates to a multi-phase lubricant, an apparatus for
lubricating with a multi-phase lubricant and a process for making a
multi-phase lubricant.
BACKGROUND OF THE INVENTION
Lubricants for industrial and automotive uses are, usually, single phase,
constant composition materials made of basestocks to which various
performance enhancing additives may be incorporated. Typically, a
lubricant is selected to optimize the performance, function and protection
of lubricated systems such as gears, cam-follower pairs, roller bearings,
hydrodynamic bearings or pumps.
To optimize system performance, the lubricant is formulated by selecting
one or more basestocks and additives which will meet system needs when
combined. Viscosity properties are an important consideration when
formulating a lubricant because the appropriate viscosity balances energy
loss because of viscous drag with wear because of diminished oil film
thickness. Antiwear and antiscuff additives can help protect surfaces when
the oil film between them thins. Basestocks, depending on their
composition, can have various beneficial properties such as antioxidancy,
good viscosity index and low traction.
While it is possible to optimize lubricant selection for a single phase
lubricant, optimum performance under the prevailing operating conditions
(such as speed, load and temperature) can be compromised when the
conditions change or when the same lubricant is used to lubricate several
parts, each part having its own unique lubricant needs. Frequently, one
lubricant is used to lubricate a wide variety of machines, for the sake of
simplicity.
The use of a single phase lubricant requires a compromise between premature
machine failure due to wear, fatigue or scuffing, because the lubricant is
of insufficient viscosity under certain operating conditions, with
excessive energy loss or overheating, because the lubricant viscosity is
too high for other operating conditions. Since machine or plant operators
prefer to minimize downtime, the compromise usually favors high viscosity
lubricants which reduce equipment failure but cause excess energy loss.
Additionally, where temperatures vary widely, the viscosity selected may
be for the weakest link component at its highest operating temperature but
because of the relationship between viscosity and temperature, much energy
is wasted since the lubricant viscosity is too high under the normally
lower operating temperatures.
A two-phase lubricant for improving the low temperature starting of an
automobile engine is disclosed in French Patent No. 2,205,931. There, a
process is disclosed in which a more dense lower viscosity phase and a
less dense higher viscosity phase are combined such that a homogeneous
phase, with lubricating properties characteristic of conventional engine
lubricants, exists when the engine is at its operating temperature. When
the engine is cool, the phases separate so that on starting the engine
under low temperature conditions only the low viscosity more dense fluid
is drawn into the oil pump. This improves engine cranking speeds because
of reduced viscous drag and provides easier starting. The disclosed
lubricants are hydrocarbons and esters, the heavier ester phase has the
lower viscosity. The objective of the patent is to ease cold starting of
an automobile engine. The patent describes the disadvantages associated
with polymers as viscosity index enhancers because they degrade with use
and cause the oil to lose viscosity. Thus, the patent suggests the use of
the two-component system as an alternative to polymers because it provides
good low temperature starting without viscosity degradation over time. The
lubricant phases mix as the engine warms-up and the mixed lubricant
behaves in the conventional manner, demonstrating large viscosity
variations with temperature.
The moving parts of industrial machines are often actuated by liquid,
usually oil, sometimes water-based emulsions, that is under pressure. The
system used to apply the liquid is a hydraulic system, usually a contained
system, which includes a reservoir, a motor driven pump, control valves, a
fluid motor and piping which connects these components. Lubricating oil is
often selected because it is useful for pressure transmission and
controlled wear and it minimizes friction and wear of moving parts and
inhibits corrosion. Hydraulic fluids with low pour points and high
viscosity indexes (VI) are formulated for use in mobile and marine
applications that are subject to temperature extremes during service. With
these high VI fluids, the goal is to obtain effective and consistent
hydraulic actuation under extremes of high and low temperatures. Although
there are many high VI hydraulic fluids available which attempt to meet
this objective, it is very difficult to do with one fluid phase that has
fairly constant properties.
SUMMARY OF THE INVENTION
The invention is directed to a process for lubricating a component of a
system which is exposed to a range of operating conditions.
More specifically, the invention is directed to a process for lubricating a
plurality of components in which each component is exposed to a range of
operating conditions. In the process of this invention, the component is
lubricated with a first lubricant whose viscosity properties are changed
as at least one condition of operation changes. For example, as the
temperature of operation increases, the viscosity of the first lubricant
is increased by the addition of a second lubricant with which it is at
least partially miscible. As the temperature of the operation decreases,
the lubricant viscosity requirements can be easily and instantly modified.
That is, the proportion of second lubricant is reduced by separation and
removal or by reducing the amount added to the first lubricant.
The invention is further directed to a closed hydraulic system in which a
first hydraulic fluid has its properties modified by the addition of a
second hydraulic fluid in which it is at least partially miscible under
the conditions which require the first hydraulic fluid to be modified. In
this embodiment of the invention, effective hydraulic actuation can be
achieved with the same closed system under extremes of conditions,
typically high and low temperatures, which are usually encountered during
marine and mobile service.
In this respect, the invention is also directed to a process for moving at
least one part of a system by circulating a hydraulic fluid.
The invention is directed to a process for lubricating an operating
component of a system in which the component is exposed to a range of
operating conditions, the process comprising:
(a) maintaining a first lubricant and a second lubricant in at least a
partial immiscibility zone under a condition sufficient for at least
partial immiscibility of the first and second lubricant, the second
lubricant is miscible with the first lubricant under a condition suitable
for miscibility and under the miscibility condition the second lubricant
changes the physical properties of the first lubricant;
(b) detecting the operating condition of the component;
(c) feeding an amount of the first lubricant and an amount of the second
lubricant to a mixing zone which is dedicated to the operating component,
the relative proportion of each lubricant dispensed to the mixing zone
being dependent upon the proportion required to achieve a third lubricant
having a property suitable for lubricating under the operating condition
detected in step (b);
(d) generating, in the mixing zone, a condition sufficient for miscibility
of the first and second lubricant to produce the third lubricant;
(e) applying the third lubricant to the component; and
(f) removing at least a portion of the third lubricant from the component.
The process further comprises the step of at least partially separating the
first lubricant from the second lubricant by subjecting the third
lubricant to a condition which makes the first lubricant at least
partially immiscible with the second lubricant.
The invention is further directed to an apparatus for lubricating an
operating component of a system in which the operating component is
exposed to a range of operating conditions which require adjustment of at
least one physical property of a lubricant which lubricates the component
during its operation, comprising:
(a) a first lubricant reservoir for containing a first lubricant;
(b) a second lubricant reservoir for containing a second lubricant having
at least one property which is different from a property of the first
lubricant;
(c) a dispenser which is operatively connected to the first and the second
lubricant reservoirs, the dispenser for supplying an amount of the first
lubricant and/or the second lubricant from the first and/or the second
lubricant reservoir to a mixing zone, the dispenser for controlling the
relative proportion of the first lubricant and the second lubricant
dispensed to the mixing zone, the mixing zone being suitable for mixing
the first lubricant and the second lubricant to produce a third lubricant,
and the mixing zone being positioned to supply the third lubricant to the
operating component;
(d) a condition sensor which detects a change in the operating condition of
the component during its operation; and
(e) an actuator which is in communication with the dispenser and which is
responsive to the condition sensor, the actuator activates the dispenser
to change the relative proportion of the first lubricant and the second
lubricant dispensed to the mixing zone in response to a change in the
operating condition which requires adjustment of at least one physical
property of the third lubricant.
In a further embodiment of the invention, the invention is directed to a
lubricant composition for a system requiring lubrication during operation,
comprising:
(a) a hydrocarbon lubricant; and
(b) a polyalkylene glycol lubricant of higher density and higher viscosity
than the hydrocarbon lubricant which influences the viscosity of the
hydrocarbon lubricant under a condition which is sufficient to make the
hydrocarbon lubricant and the polyalkylene glycol lubricant at least
partially miscible.
In a still further embodiment, the invention is directed to an apparatus
for lubricating an operating component of a system in which the operating
component is exposed to a variation in a condition of operation which
requires adjusting at least one physical property of the lubricant which
lubricates the component during operation, comprising:
(a) a reservoir comprising a first lubricant of low density and low
viscosity and a second lubricant of higher density and higher viscosity
than the first lubricant, the second lubricant is immiscible with the
first lubricant under an operating condition suitable for immiscibility;
(b) a third lubricant comprising at least a partial mixture of the first
lubricant and the second lubricant which partial mixture forms within the
reservoir under an operating condition suitable for at least partial
miscibility of the first lubricant and the second lubricant;
(c) an operating component, at least a portion of the operating component
being located within the reservoir and in contact with the first lubricant
of low density and low viscosity, under a condition of immiscibility, and
the operating component being in contact with the third lubricant under an
operating condition suitable for at least partial miscibility of the first
lubricant and the second lubricant.
Still further, the invention is directed to a process for lubricating an
operating component of a system in which the operating component is
exposed to a variation in a condition of operation, comprising:
(a) maintaining a first lubricant of low density and low viscosity and a
second lubricant of higher density and higher viscosity than the first
lubricant in a lubricating zone under an operating condition in which the
first lubricant and the second lubricant are partially immiscible;
(b) contacting the operating component with the first lubricant under the
operating condition of immiscibility; and
(c) conducting the contacting of the operating component under an operating
condition which is different from the operating condition of step (b) and
which is suitable for at least partial miscibility of the first lubricant
and the second lubricant which forms a third lubricant.
In yet another embodiment of the invention, the invention is directed to a
closed hydraulic system in which hydraulic actuation is applied to move at
least one part of a system by a circulating hydraulic fluid comprising
(a) an at least partial immiscibility zone which contains a first hydraulic
fluid and a second hydraulic fluid under a condition sufficient for at
least partial immiscibility of the first and second hydraulic fluids, the
second hydraulic fluid is at least partially miscible with the first
hydraulic fluid under a condition suitable for at least partial
miscibility and under this miscibility condition the second hydraulic
fluid changes a physical property of the first hydraulic fluid;
(b) at least one hydraulic actuator for providing hydraulic force to the
part of the system;
(c) a controller for driving the hydraulic actuator;
(d) a mixing zone associated with the at least partial immiscibility zone,
the mixing zone for containing the first and second hydraulic fluids which
are in a state of at least partial immiscibility when there is a condition
for at least partial immiscibility; and
(e) at least one pump for providing the first and second hydraulic fluids
which are in a state of at least partial immiscibility from the mixing
zone to the hydraulic actuator when a condition suitable for miscibility
occurs.
The lubricants are, typically, at least partially miscible. Although the
lubricants can be totally miscible, this can be difficult to achieve.
Therefore, in specific terms, the lubricants are substantially miscible.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified schematic flow diagram of the process of this
invention.
FIG. 2 is a simplified schematic drawing of an apparatus contemplated for
carrying out this invention.
FIG. 3 is a simplified schematic drawing of an alternative apparatus for
carrying out the invention.
FIG. 4 is an alternative embodiment of the apparatus shown in FIG. 3.
FIG. 5 is a viscosity-temperature plot for several single phase lubricants.
FIG. 6 is a viscosity-temperature plot of mixed lubricants containing two
fluids in various proportions.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of the invention, there are at least two different phases
of lubricant. The term "different phase" is used here to mean a physical
difference between the lubricants which makes them separable under a
certain condition. Typically, the first phase lubricant is a low viscosity
material and the second phase lubricant is a high viscosity material. The
second lubricant can be referred to as a contributor in that its
combination with the first lubricant contributes certain properties, such
as a different viscosity, which will modify the first phase lubricant
thereby producing a third lubricant. Typically, a density difference
between the two phases allow easy separation to occur under conditions
which cause the phases to be immiscible.
Typical lubricants which can be used in the invention are miscible in any
proportion at temperatures ranging from above about 20.degree. C. to about
100.degree. C., depending upon the application. However, the proportion of
each lubricant can influence miscibility, depending upon the
characteristics of the lubricant. Typically, as the viscosity difference
between the lubricants increases their miscibility decreases and reduced
amounts of the more viscous material and/or more severe mixing conditions,
may be required to maintain miscibility of the lubricants.
Although, typically the second phase is a liquid, it can also be a solid or
gas which dissolves into the first phase at certain operating conditions
such as elevated temperatures and pressures. A specifically contemplated
solid is a wax which would mix in with the lower viscosity first phase
during high temperature operation to increase its viscosity.
Alternatively, there can be an immiscible solid or liquid which contains a
material that releases into the first phase in response to a changing
operating condition, such as an increased temperature.
The density of one of the phases can be sufficiently higher than the
density of the other phase to facilitate separation. Although difficult to
quantify, a density difference of at least about 0.02 gm/cc and preferably
at least about 0.08 gm/cc should be sufficient for separation by gravity.
The term miscible is used here to indicate when the phases are uniformly
dispersed in each other. Ideally, when the phases of lubricant are
subjected to a condition which makes them uniformly dispersed in each
other, they form a single phase. However, to be useful, the lubricants
need only be at least partially miscible, preferably substantially
miscible.
The choice of materials employed for each phase will depend upon the
conditions of the system and the optimum viscosity needed for the machine
element to be lubricated.
The following are alternative embodiments showing various applications in
which the lubricant system can be employed.
The invention has utility in lubricant circulation systems used on
machines, such as a paper machines, printing presses or machine tools,
which have many components each operating under different conditions (e.g.
temperature). The invention also has utility in lubricant circulation
systems used in multi-machine plants such as manufacturing or power
generating facilities which have a number of machines operating under a
wide variety of conditions.
The invention will be useful in gearboxes which operate over a range of
temperatures and operating conditions, in particular, in multiple
reduction gearboxes where the gear contacts for the various reductions
have different lubricant needs.
The invention can also be used as a method for controlling fluid viscosity
in hydraulic systems. These systems are found on off-highway equipment and
on ships and are subjected to a variety of ambient temperatures under
which they must perform. The invention alleviates the large changes in
hydraulic fluid viscosity with temperature which compromise performance.
In closed hydraulic systems in which there is a circulating first hydraulic
fluid, the invention is useful for modifying or controlling at least one
property of the circulating first fluid. Either automatically upon a
change in an operating condition or upon detecting a change in at least
one operating condition such as an increase in temperature, a second
hydraulic fluid which will change at least one property of the first
hydraulic fluid when the two become miscible is mixed with the first
fluid. Thus, in a typical system, the second hydraulic fluid will elevate
the viscosity of the first hydraulic fluid when the operating temperatures
increase to facilitate hydraulic operation under those reduced
temperatures.
The hydraulic system of this invention will be useful when applied to
machine tools, presses, draw benches, elevators, jacks and mining
machinery. It will typically be useful for lifts used in the marine
environment and on other mobile equipment which is exposed to the vast
temperature fluctuations which may occur near molten metal, open flames
and travel from cold climates (e.g. the arctic) to hot climates.
It is further contemplated that the invention will be useful in engines
such as large diesel engines and aviation or stationary gas turbines where
lubricant oil volumes or critical component needs may economically justify
the addition of a phase separation and circulation system.
This invention can also be used for stability control of hydrodynamic
bearings. The ability to control viscosity, as disclosed herein, can be
used to bypass certain unstable operating conditions without the need to
alter speed or load.
The invention can also minimize energy losses in circulation systems
feeding hydrostatic bearings by optimizing the viscosity needed to support
the bearing loads.
It is further contemplated that the invention will be useful for additive
treatment of lubricants. In this regard, selective additive miscibility in
one of the phases would allow additives to be delivered at the point of
need. This will keep them away from parts which they may harm.
The invention will also allow for varying basestock properties such as
traction force generation under shearing conditions. A high degree of
traction force generation in certain types of components is desired to
prevent slip. Yet, a low degree of this property is desired in other types
of components to reduce friction losses and heat generation. With the
multi-phase lubricant, the lubrication requirements of both types of
components can be met without compromising either.
Implementation of the invention can be passive or active. A passive system
is exemplified by a machine where the components, such as the gears, are
lubricated by contact with the single phase lubricant. In one embodiment,
the component is dipped into an upper layer of lubricant, the less dense
phase, located within the sump. The higher density phase, located in a
lower layer does not contact the component until the temperature of the
machine increases sufficiently to cause increasing amounts of the high
density lubricant to mix with the low density lubricant. In this
embodiment, the high density lubricant is selected to have a high
viscosity so that the mixed lubricant will more effectively lubricate
under the high temperature conditions. As the temperature decreases, the
lubricants will separate and the lower density material which is selected
for its low viscosity will lubricate.
An active system utilizes a manual, mechanical or electromechanical control
to determine the proportion of each lubricant necessary to achieve optimum
lubricant properties. The lubricants are mixed and distributed to the
component to be lubricated. After use, the lubricant is collected and
brought to a separator for separating and reuse.
Because one aspect of this invention includes separating the multi-phase
lubricant, after use, into phases rich in the starting lubricants which
are then remixed and reused, it is important that each lubricant be
sufficiently physically or chemically different so that they are at least
partially immiscible under certain conditions.
Specifically contemplated methods of separating the lubricants include
gravitational separation, e.g. in a holding tank, where the density
difference is sufficient to allow separation by this method or by use of a
centrifuge, hydrocyclone or other apparatus which enhances gravitational
separation. Other separation systems can be used and those contemplated
include membrane separation and solvent separation. Although not a
preferred form of separation, distillation may also be employed.
FIG. 1 is a simplified schematic flow diagram of one embodiment of the
invention. A first lubricant reservoir 10 contains a lubricant of a first
viscosity. A second lubricant reservoir 12 contains a lubricant of a
second viscosity. Each lubricant reservoir is associated with a dispenser
14. An example of a suitable dispenser is a pump typically a plurality of
pumps. The lubricant from each lubricant reservoir is transferred to
mixing zones 18a and 18b via the dispenser 17 through conduits 15a, 15b,
16a and 16b. The mixing zones 18a and 18b are associated with operating
components 22a and 22b. In the drawing two operating components are shown
to demonstrate that a plurality of operating components, each having
distinct lubrication requirements, can be handled by this system. The
dispenser has the ability to control the flow of lubricant from the
reservoir to the mixing zone. Although, in the drawing, the operating
component is separate from the mixing zone and connected through lines 17a
and 17b, they can be more closely associated. That is, the mixing zone can
be located about the operating component. For example, in a roller
bearing, the mixing zone can be the zone of lubricant which lubricates the
bearing. Condition sensors 26a and 26b are situated to detect a change in
the operating condition of either or both components during their
operation. The condition sensors can comprise a temperature measuring
device 25a and 25b, such as a thermometer, or a viscometer. Thus, the
detectable change can be in the operating temperature of the component or
the viscosity or temperature of the lubricant which lubricates the
component or any other measurable operating condition. The condition
sensors provide information, concerning the operating condition, to
actuators 24a and 24b which are in communication with the dispenser 14. In
response to a change in an operating condition of either component 22a or
22b, detected by the condition sensor, the actuator activates the
dispenser to adjust the proportion of the first and/or second lubricants
dispensed to the mixing zone. In this manner, a property of the lubricant,
such as viscosity, can be increased or decreased in response to an
operating condition to which the component is exposed. Specific examples
of operating components which will benefit from this device are a bearing,
such as a ball or roller bearing or gears. In a specific example, the
dispenser is a pair of pumps pressurizing lubricants from lines 15a and
15b and a series of valves individually controlling the proportions of the
lubricants being sent to a multiplicity of components such as 22a and 22b
via lines such as 16a and 16b. The individual settings on the valves can
be determined through an algorithm determining the needs of the components
based on inputs from operating condition sensors 24a and 24b. The third
lubricant is withdrawn from the component via lines 29a and b. Optionally,
the first lubricant is at least partially separated from the second
lubricant under a condition sufficient to make them immiscible. Thereafter
the lubricants can be reused by returning them to the lubricant reservoirs
or discarded.
FIG. 2 is another simplified schematic flow diagram of one embodiment of
the invention. In FIG. 2, there is shown a first lubricant reservoir 10
and a second lubricant reservoir 12 each containing a lubricant having a
different density. An amount of lubricant is withdrawn from each reservoir
via lines 30 and 31 each having a pump 32 and 33. Alternatively, each
lubricant may be drawn from separation zone 34, the lower density
lubricant withdrawn from the top of the zone via line 35 and the higher
density lubricant withdrawn from the bottom of the zone via line 36. The
lubricants are passed to at least one mixer zone, such as a first mixer
zone 37 and a second mixer zone 38 via lines 39a and 39b. Each mixer zone
is dedicated to a component or a set of components having similar
lubrication needs. In the mixer zones, the first and second lubricants are
combined in proportions determined to produce a single phase lubricant
meeting the needs of the component(s) assigned to that mixing zone. This
can be aided, if necessary, by heating and/or stirring. An example of how
the proportions of each phase to be mixed in each mixing zone may be
determined is through the use of a microprocessor or computer which
receives feedback on the operating condition of the component such as
temperature, speed and load and uses an algorithm designed to determine
the viscosity needs of that component. Viscosity control may also be aided
by in-line viscosity sensors in the supply lines of the individual phases
or in the output line from the mixing zone to the component. Flow rates
needed for cooling or for adequate lubrication can also be determined
using a similar data processing method. The single or mixed phase
lubricant flows from each mixer zone to its associated components such as
a gear 41a or a bearing 41b via lines 40a and 40b. After performing its
lubricating function, the lubricant flows back to a lubricant separator
comprising at least one collection zone 44 and optionally, a cooling zone
45. The collected lubricant is then passed to the separation zone 34 which
separates the first phase from the second phase. Each separated phase can
be, optionally, filtered and, optionally, returned to its reservoir for
re-use.
FIG. 3 is a further embodiment of the invention. In FIG. 3, there is at
least one operating component which requires lubrication for effective
performance, such as a gear 50. The operating component is exposed to a
variety of conditions during operation, e.g., high and low temperatures,
which require adjusting at least one physical property of the lubricant.
At least a portion of the operating component, e.g. the gear teeth 52, in
the case of a gear, are located within a lubricant reservoir 54. The
lubricant reservoir comprises a first lubricant of low density and,
usually, of low viscosity 56 and a second lubricant 58 of higher density
and, usually, higher viscosity than the first lubricant. The first and
second lubricants are immiscible during certain operating conditions,
usually at lower temperatures, e.g. ambient temperatures. Under operating
conditions which promote miscibility of the lubricants, such as higher
temperatures, the first and second lubricants mix, at least partially.
When this occurs, a third lubricant forms having a property which is
different from the first or the second lubricant. Usually, it has a
different viscosity. This third lubricant comes into contact with the
operating component and is more appropriate for lubricating the component
under the condition which causes the mixing than either the first
lubricant or the second lubricant. The used lubricant can be drained back
into the reservoir for re-use.
In FIG. 4 an alternative apparatus is shown. In FIG. 4 the operating
component or set of gears are located outside of the lubricant reservoir
64 and the lubricant is drawn from the top of the reservoir and
transmitted to the gears 62 via line 70. A low density, usually low
viscosity, lubricant is a first lubricant 66 and a second lubricant of
higher density, and usually higher viscosity, is located below it in the
bottom portion of the reservoir. The first lubricant is withdrawn from the
top of the reservoir and transmitted to the gear via a pump or siphon
under operating conditions which cause the lubricants to be immiscible.
When the operating conditions change, causing the lubricants to be
miscible, e.g., when operating temperatures increase, the lubricants mix.
When this occurs, a third lubricant forms. The third lubricant has a
property which is appropriate for lubricating the component under the
changed operating condition. The used lubricant can be removed from the
component and transferred back to the reservoir (not shown).
In both FIG. 3 and FIG. 4, the third lubricant will separate into the first
and second lubricant when an operating condition which promotes
immiscibility occurs, e.g., when the operating temperature drops.
In a more specific embodiment of the invention, a lubricant phase employed
is a polyoxyalkylene compound, specifically a polyoxyalkylene liquid
lubricant. Polyoxyalkylenes are described in Gunderson and Hart, Synthetic
Lubricants (1962) at pages 61-101 which is incorporated herein by
reference as to the description of the polyoxyalkylenes. Th | | |
