FIELD OF INVENTION
This invention relates to a counter balance valve for load independent flow/
speed control in lowering to avoid slow and fast dropping of light and heavy
implements.
BACKGROUNDIPRIOR ART OF THE INVENTION
During lowering of a heavy implement, the lowering time is less as the
implement comes down under its own weight quickly and smoothly, whereas
during lowering of a light implement, the lowering time extends and it is
accommodated with jerks.
The basic operations involved in functioning of a lift are as follows:
Lifting:
The Circuit lever (Red Lever) is set to the Lift mode, by which the oil flows from
the pump to hydraulic cylinder through internal hydraulic circuit. At the same
time the path of the external hydraulic lift system is closed; hence, no oil
passes through the external hydraulic system.
Holding position:
The Circuit lever (Red Lever) is set to the internal hydraulic mode. By doing so
rotary oil distributor direction gets reverse and the circuit becomes internal.
Then the hydraulic oil flows from the pump to the internal circuit through the
rotary oil distributor. In the internal hydraulic circuit the oil flows straight from
the distributor to the tank/ sump.
Lowering:
For lowering, the Circuit lever is kept at External and Internal mode. Due to
which the rotary oil distributor orientation is set at the middle, and the oil,
which flows from the pump, subsequently .flows to the sump through the rotary
oil distributor and the distributor.
While lowering, a general problem arises i.e. difference in the lowering time of
heavy loads and light loads. During lowering of a heavy implement, the
lowering time is less as the implement comes down under its own weight
quickly and smoothly, whereas during lowering of a light implement, the
lowering time extends and it is done with jerks.
Hence, the present invention introduces a counterbalance valve for load
independent flow/ speed control in lowering to avoid the problem of slow & fast
dropping of light and heavy implements respectively.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a counter balance
valve for load independent flow/ speed control in lowering to avoid slow and
fast dropping of light and heavy implements which overcomes disadvantages
associated with the prior art.
Another object of the present invention is to provide a counter balance valve for
load independent flow/ speed control in lowering to avoid slow and fast
dropping of light and heavy implements which is simple in construction.
Further object of the present invention is to provide a counter balance valve for
load independent flow/ speed control in lowering to avoid slow and fast
dropping of light and heavy implements whichSis reliable.
SUMMARY OF THE INVENTION
According to this invention, there is provided a counter balance valve for load
independent flow/ speed control in lowering to avoid slow and fast dropping of
light and heavy implements comprising an enclosure accommodating a spool at
one end and a spring at other end, which is located between a wall and a
stopper.
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 and 2 shows: Counter balance valve according to present invention.
Fig.3 shows: Pressure compensated flow control valve in accordance
with present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS:
This invention discloses a counter balance valve for load independent flow/
speed control in lowering to avoid slow and fast dropping of light and heavy
implements.
Reference may be made to fig. 1, wherein the counter balance valve of invention
comprising an enclosure (housing) (1) accommodating a bush (2) at one end.
The bush (2) houses a spool (3). Further, there is provision of another bush (4)
accommodating a spring (5). The spring is located between a wall (6) on one
side and a stopper (7) on other side. The stopper constitutes a pin which acts
as a stopper for spool valve. It provides a limit to the movement of the spool.
Both the bushes provide rigid enclosure for the moving parts i.e. spool, spring
etc. The spool actually moves against the spring force. The spring provides
restoring force to the spool, so that it may come back to its original position.
Reference may be made to fig. 2 and 3, wherein at port A, oil comes from
cylinder through the check valve and flows out to the tanklsump via port B. If
the spool E is moved towards right, the port B would start closing and thus the
flow through the orifice would be reduced. Hence the flow of the return oil
depends upon the orifice opening. This movement of spool is done with the help
of pilot pressure in the region C through pilot line present in the spool. Here
the oil flows through an opening and the pressure created in the region (C)
depends upon the pressure acting on the cylinder due to the load acting on the
hydraulic cylinder. If there is a heavier implement, then it would exert higher
force thus more pressure is created and if there is a lighter implement then it
would exert a smaller force and thus less pressure is created in this region. For
all the forces to be in equilibrium, at every instant there is a balance between
this pressure force and spring force Fs. If there won't have been the spring
force the spool would move rightwards and there would be no restoring force
which could help the spool to come back in its original position when the load
is removed. Here this restoring force is provided by the spring and at every
instant, the spring force balances the pressure force. If the pressure is
increased in the region C, then it will move the the spool E towards right.
As Fs(Spring Force)=kx, therefore if x is increased, force is increased.
Thus with the increase of pressure, the displacement and hence spring force
also increases and keeps the system in equilibrium.
Now, if a lighter implement is attached with the system, a small amount of
pressure is exerted on the spool E. Therefore, the orifice or the port B would be
open to provide a higher discharge. Due to this, the rate of flow of oil to the
tank would be higher which helps the implement to come down quickly and
smoothly. If a heavier implement is attached to the system, it would exert a
higher force and thus higher pressure force would be exerted at the spool,
which moves the spool to reduce the opening area of the port B and hence the
discharge through the orifice is reduced. This reduces the rate of flow of oil and
hence the lowering time is increased during the attachment of a heavier
implement.
Hence incorporation of counterbalance valve makes the flow/ speed control load
independent in lowering to avoid the problem of slow & fast dropping of light &
heavy implements respectively.
Advantageous features
Lowering time is made same and uniform for both heavy and light
implements.
Slow dropping of light implements is avoided.
Damped and full dropping results in smooth but fast lowering.
Risk of accident due to fast dropping of a heavier implement is reduced.
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 invention are intended to be within
the scope of the present invention, which is further set forth under the
following claims: -

We Claim:
1. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
comprising of an enclosure accommodating a spool at one end and a
spring at other end, which is located between a wall and a stopper.
2. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
as claimed in claim 1, wherein the spool and spring is accommodated in
respective bush and the stopper constitutes a pin, that acts as a stopper
for spool valve.
3. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
as claimed in claim 1 or 2, comprising an inlet-port for supply of oil from
cylinder through check valve and an outlet port for outflow of oil to
tankljump together with the spool for closure of said outlet.
4. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
as claimed in any of the preceding claims, wherein the spool, movement
of which is carried out by means of pilot pressure in a region through
pilot line in the spool, in which the spool moves against the spring force.
5. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
as claimed in any of the preceding claims, wherein the pressure created
in the region depends on the pressure acting on the cylinder due to the
load acting on the hydraulic cylinder.
6. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
as claimed in any of the preceding claims, wherein the spring provides
restoring force onto the spool.
7. A counter balance valve for load independent flowlspeed control in
lowering to avoid slow and fast dropping of light and heavy implements
substantially as herein described with reference to the accompanying
drawings.