FIELD OF INVENTION
This invention relates to an improved hydraulic lift of a vehicle.
PRIOR ART
In the currently available hydraulic lift, the circuit lever (Red Lever) is set
to the internal mode. Then, the Selection lever is kept in position control
or draft control and, finally, the main control lever is kept in the drop
zone. After starting the tractor, the temperature of the hydraulic oil is
between 10-l4°C. In neutral condition, this oil passes from the pressure
pipe through the main control valve passages and finally to the reservoir
(Center Housing) and, from the reservoir (Center Housing) it passes
through the suction pipe to hydraulic filter and hydraulic pump, this
cycle keeps on repeating. Since, the temperature of the oil is less, the
viscosity of such oil is high, due to which flowability decreases and the
stickiness increases. This stickiness causes the hydraulic filter to choke
and hence the hydraulic filter safety valve opens, due, to which all the
impurities flow freely in the system, hence, the basic functioning of the
filter fails. These impurities pass through the hydraulic pump and the
hydraulic lift. These impurities causes severe damage to the pump,
control valve assembly, pipes- suction and pressure and the filter itself.
Major damage in any of the components will severely hamper the lifting
capacity of a lift.
J ' ' J
-3-
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an improved
hydraulic lift of a vehicle which overcomes disadvantage(s) associated
with the known art(s).
Another object of the present invention is to provide an improved
hydraulic lift of a vehicle which is simple in construction.
Further object of the present invention 1s to provide an improved
hydraulic lift of a vehicle which is efficient.
SUMMARY OF THE INVENTION
Hydraulic system of an agricultural tractor is an open center hydraulic
system which, comprises of positive displacement hydraulic pump,
control valve assembly, filter assembly, cylinder, piston, cylinder, ram
arm, serration shaft and control linkages. Presently agricultural tractors
are equipped with automatic depth and draft control system. current
applications of agricultural tractors is the filed operations and, also, road
applications with focus on Construction & Industrial application.
Being an open center system with positive displacement gear pump
directly mounted on engine, hydraulic system is running as long as the
engine is running, hence, the system is called "Live Hydraulic system".
When the tractor is started, the temperature of the hydraulic oil is
between 10-l4°C in winters. In neutral condition this oil passes from the
pressure pipe through the main control valve passages and finally to the
I '
-4-
reservoir (Center Housing) and, from the reservoir (Center Housing) it
passes through the suction pipe to hydraulic filter and hydraulic pump,
this cycle keeps on repeating. Since, the temperature of the oil is less,
the viscosity of such oil is high, due to which flowability decreases and
the stickiness increases. This causes the hydraulic filter safety valve to
open partially, hence, all the unfiltered oil circulates throughout the
system/circle, causing damage to the components.
It is therefore proposed in the present invention to bypass oil at such
temperature to the reservoir (Center Housing) and not allowing the oil to
go into the control valve assembly, till, the temperature of the oil
increases to 30°c. Then the oil is allowed into the hydraulic lift. This
prevents the damage of the components of the hydraulic lift and
deterioration of performance of system.
STATEMENT OF INVENTION
According to this invention, there is provided an improved hydraulic lift
of a vehicle comprising of a bypass valve provided before directional
control valve.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Further objects and advantages of this invention will be more apparent
from the ensuing description when read in_ conjunction with the
accompanying drawings and wherein:
Fig. 1 shows: bypass of oil into the reservoir (Oil (Temp 12-14°C) being
Bypassed into the Reservoir.
...
-5-
Fig. 2 shows: oil being routed back into the main control valve (Oil
(>Temp 30°C) being routed into the main control valve.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO
THE ACCOMPANYING DRAWINGS:-
Due to above said problems, it is required to bypass the flow of oil before
the main control valve assembly to reservoir (centre housing) till, the
temperature of oil is less than 30°C. This causes increase in oil
temperature and reduction in the stickiness and viscosity. So, the
flowability is greater and this in turn will not cause the opening of the
filter valve.
Further, lifting capacity and overall efficiency of the hydraulic system will
be maintained.
According to this invention, there is provided an improved hydraulic lift
comprising of introduction of bypass valve before the directional control
valve.
The Circuit Lever (Red Lever) is set to the internal mode. Then, the
Selection lever is kept in position control or draft control, and finally, the
main control lever is kept in the drop zone. By providing a bypass valve
before the main control valve assembly, the damage to the hydraulic
system can be reduced. The oil instead of going to the main control valve
assembly will be diverted to the reservoir. Once the temperature of the oil
increases, the oil .. is again diverted back to the main control valve
assembly. This modification can be seen in the figures 1 and 2.
' .
-6-
OPERATION
The Circuit lever (Red Lever) is set to the internal mode. Then, the
Selection lever is kept in position control or draft control and, finally, the
main control lever is kept in the drop zone. After starting the tractor, the
temperature of the hydraulic oil is between 10-l4°c. Now, in neutral
condition the oil will pass from the pressure pipe to the bypass valve and
finally to the reservoir (Center Housing) and, from the reservoir (Center
Housing) it passes through the suction pipe to hydraulic filter and
hydraulic pump, this cycle keeps on repeating. Herewith, the oil will not
pass through the main control valve. There will be a crack off in the
passage of the bypass valve which will allow the oil to directly be
bypassed into the reservoir. This passage opens because at low
temperature of the oil the viscosity is high, due to which flowability
decreases and the stickiness increases, and, hence, this creates a high
pressure drop in the system which causes the passage of the bypass
valve open. This passage will cause the oil to directly go into the
reservoir. Hence, even if the filter safety valve is opened this will not
cause any harm to the components as the oil will not pass into the main
control valve.
Once the temperature of the oil increases the viscosity will decrease and,
the pressure drop of the system will decrease. So, the filter safety valve
will not open, hence, filtered oil will pass from the filter. Also, the
pressure drop will be less, bypass valve will not open and, the oil will flow
directly into the main control valve. Therefore, the oil that reaches the
main control valve will have impurities within the parameter.
-7-
Thus, life of the hydraulic system and components will increase by
introducing Bypass valve.
Advantageous features
Increase in life of the components( distributor, pressure relief valve & ram
cylinder) of the hydraulic lift.
Decrease in clogging of main control valve, and , hence, reduction m
sticking of the hydraulic lift.
It is to be noted that the present invention IS susceptible to
modifications, adaptations and changes by those skilled in the art.
Such variant embodiments employing the concepts and features of this

WE CLAIM:
1. An improved hydraulic lift of a vehicle comprising of a bypass valve
provided before directional control valve.
2. An improved hydraulic lift as claimed in claim 1, wherein the lift
bypasses the flow of oil before the main control valve assembly to
reservoir till the temperature of oil is less than 30°C.
3. An improved hydraulic lift as claimed in claim 1 or 2, wherein
provision of bypass valve before the main control valve assembly
reduces damage to the hydraulic system.
4. An improved hydraulic lift as claimed in any of the preceding
claims, wherein the oil instead of flowing to the main control valve
assembly is diverted to the reservoir in which once the temperature
of the oil increases, the oil is again diverted back to the main
control valve assembly as shown in fig.l and 2.
5. An improved hydraulic lift of a vehicle substantially as herein
described with reference to the accompanying drawings.