Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method and an apparatus for cleaning
hydraulic and transmission oil.
In civil engineering, forestry and other fields, the use of
machinery equipment has increased in recent years. Machines of this kind
usually comprise at least one hydraulic system. The system includes a certain
amount of hydraulic oil, depending on the work to be carried out and on the
size of the machine. Said amount normally varies between 50 and 1000 litres.
The development of machines in this field shows the tendency
towards increased use of hydraulic systems instead of cable drive and towards
increasing size of the hydraulic system in each type of machine. A further
development trend is the utilization of an increasingly greater number of ~ ;
machines in order to render the work at construction sites and in forestry
more efficient.
In machines of the kind concerned the hydraulic oil must be
changed at certain intervals, according to recammendations usually after every
500 to 1000 operation hours, i.e. at least three times a year. The oil change
is to be made at the place of the machine, i.e. in the field, because it
would be much too expensive to return the machine to a machine shop or the
like.
The oil change involves costs for new oil and for the change
proper, and it includes work and inconveiences in conjuntion with the forward-
ing of new oil and the draining of the spent oil on the ground.
The ommission of oil change involves the risk of highly~expensive
repairs and shutdowns, owing to damage or too early wear of primarily bearings,
gears and cylinders, caused by wearing impurities, with during the operation
accumulate in the oil tank of the machine.
It is, therefore, impossible not to change the oil, although the
oil consumption and drainage create substantial inconveniences from an eco-
nomic as well as nature protection point of view. Of course these inconven-
iences grow rapidly with the expansion of the machine stock. ~ -
The present invention, thus seeks a method of removing the
hydraulic oil from the machine, subjecting the oil at the place of the machine,
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i.e. in the field, to a certain treatment and returning the oil to the machine
for continued use.
Hydraulic and transmission oil of the type in question consists
of a base oil with additives.
The base oil is indestructible at the conditions prevailing in
the machines. Unlike motor oil, it does not come into contact with hot machine
parts, diluting engine fuel or exhaust gases.
Certain of the additives may possibly be inactivated due to ageing
or wear. They are, however, with respect to volume and costs, only an insigni-
ficant part of the oil and, therefore, can be regenerated by small additions.
The reason why hydraulic and transmission oil is changed after500 to 1000 operation hours lies exclusively in the risk that the oil may be
contaminated by solid impurities, wearing metal chips and the like, which
accumulate in the oil tank.
The oil to the working cylinders etc. is taken from some height
above the tank bottom and pumped via valves to the cylinders etc. A partial
stream flows from the pump to an oil filter and returns to the tank. This
provides a certain protection, particularly against impurities, which remain
suspended in the oil and, therefore, arrive at the filter sooner or later.
This does not prevent, however, larger particles, which from an operation
point of view are more dangerous, accumulate on the tank bottom and constitute
a growing risk.
As in the case of the previous type of oil changes, it is there-
fore necessary to be able to drain the oil from the tank rapidly at certain
intervals. For this purpose, the tank is designed so that its bottom is
thereby flushed clean. According to the invention, the oil is filtered and
thereafter returned to the machine. If additives are deemed necessary, they
may possibly be added simultaneously.
In this way, the number of oil changes can be reduced or elimi-
nated entirely. The oil changes, besides, can be carried out at occasionswhen they involve the least inconvenience, and the waste oil can be taken
care of in a manner acceptable to the environment. -
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By the method according to the invention, the oil costs can be
reduced substantially. The costs for one charge of oil are at present SwCr
150 to 200 for the smallest machines and about 3000 for the largest ones. The
oil is changed about five times a year.
A further advantage of the invention is the decrease in oil
import which a re-utilization of the oil would imply. At the present level of
costs this would mean, in Sweden alone, roughly estimated a decrease in oil
import by SwCr 25 millions.
Accordingly, moreover, the emission of oil into the environment
would be reduced corresponding to the decrease in imports.
The invention, furthermore, renders the work of the machine
operator much easier as he need no longer handle heavy oil drums.
A further advantage, with respect to fault localization and
preventive maintenance, is that the "oil change" can be moved forward at the
slightest suspicion of abnormal wear, because the change is so much simpler
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and cheaper. The filter may also be changed and controlled more often in
order to discover at an early stage possible abnormal wear.
The invention is described in greater detail in the following,
with reference to the accompanying drawing. The invention can be worked with
or without access to an oil pump. Figure 1 shows how the invention can be -
worked without a pump, Figure 2 shows the use of a pump.
Referring to Figure 1, the oil is drained from the machine 7 into
a trough 1 placed below the machine. From the trough the oil is poured into
a can 6 and then poured into a funnel 2, from ~bich the oil runs through a
filter 4 down into a canister 5. From this canister the oil is returned to
the hydraulic system.
Figure 2 shows how the invention can be applied with access to
an oil pump 8. By means of this pump the oil is pumped from the trough 1 to
the filtering vessel 2, through the filter 4 and back to the oil tank 7 of -
the machine.
At draining, the trough 1 is placed below the drainage plug of -
the machine. Troughs of this kind may be available in a limited number of
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sizes, which together shall cover all existing machine types. The trough
preferably is made of sheet metal or glass-fibre-reinforced polyester plastic
and provided with stiffenings and runners so as to withstand handling on
uneven ground.
The filtering vessel 2 according to the invention comprises a
holder (frame) for a filter, a sealing thereabout and on one side of the
filter a vessel, which either by its dimensions or in combination with the
application of an oil pump provides the necessary filtering pressure.
The filter 4 used according to the invention is made of paper in
folded form and intended to be disposable. After use, it may be burnt.
When a high filtering speed is received both a suitable filter
medium and a large filter area are re~uired. A suitable filter medium for
separating relatively large solid particles from the oil is paper, which
should have a substance of 30 - 150 g/m2 and a Gurley density below 1:0 s/100
ml.
In order to obtain a large filter area within the given outer
dimensions, the filter paper is folded. For preventing reduction of the filter
area, adjacent paper surfaces are prevented from abutting each other by em-
bossing (creping) the paper web prior to the folding operation or by coating
it with lines of plastic or the like in longitudinal direction, or by fixing
the ridges of the filter at a desired spaced relationship subsequent to the
folding operation.
The folded filter paper may be made into plane or cylindrical
filter elements, as desired.
In the method in general either an oil pump or canisters of, for
example, 20 litres are used, which are formed so as to render it possible to
pour the oil back into the hydraulic system, and further cans of, for example,
10 litres for pouring the oil from the ~rough to the funnel.
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