FIELD OF INVENTION:
The present invention relates to, a constant flow smooth jerk-free
hydrostatic steering system, using lever operated steering valve and, use of
excess flow to secondary operations with smooth switching, generally being
used in pick and carry type of cranes.
BACKGROUND OF INVENTION:
Lever operated steering system is known in the art.
In the known steering system for pick and carry type of cranes, using
lever operated steering systems, the full flow of oil passes through the direction
control valve to flow control valve and creates a sudden jerk.
On operation of valve lever, the oil is diverted to steering cylinder where
the oil is metered in by a pressure compensated flow control valve. The balance
oil is diverted to the tank. The steering system is protected by a relief valve
which is inbuilt in the flow control spool. A main relief valve protects the over
all system.
As is apparent the known system is full of disadvantages.
The main disadvantage of the known steering system as outlined above is,
that the full flow oil diverted through direction control valve to flow control
valve, causes a time lag in operation of flow control spool, thereby causing a
flow spike resulting in a reactive fast steering which is quite unsafe.

-2-
Another disadvantage of the known steering system is that the relief valve
for steering protection gives high over ride at high flow.
Yet another disadvantage of the present steering system is that the excess
oil at steering is unused and is diverted to the tank. Also, in the present steering
system, this oil can not be used for other operations.
Yet another disadvantage of the known steering system is, the necessity
to install two sets of flow control and relief valves on both lines of cylinder, and
hence suffers from the possibility of time lag on either side operations of
steering cylinders.
Yet another disadvantage of the known steering system is that the system
in total becomes quite bulky.
It has, therefore, been long felt need to develop a system which removes
the disadvantages mentioned above and is economical, easier, eco-friendly and
cheaper to operate.
Therefore, in view of the disadvantages stated above, the main objective
of the present invention is to describe a smooth steering system wherein the
steering oil is controlled before the direction control valve by the use of
balanced spool pressure compensated flow control valve and, further metered at
direction control valve, thereby avoiding flow spikes and making the system
more safe and jerk-free. By using a single flow control valve, in the present

-3-
invention, the problem of time lag on either side operations of steering cylinders
is eliminated.
Another object of the present invention is, to increase the efficiency of
the hydraulic system, by combining steering oil flow to main hydraulics and,
thus facilitating the use of excess oil for other operations, during steering.
Another object of the present invention is, to facilitate a smooth switching
of the oil from steering valve to main hydraulics.
Yet another object of the present invention is, to use a single steering
system relief valve by using a special spool in steering direction control valve.
Further object of the present invention is, to make the overall system
compact, by combining steering control functions at the main control valve and
designing the steering valve for low flow and thus optimizing the connected
piping.
These and other objects are achieved by the improved lever operated
steering systems for cranes of the present invention.
According to present invention there is provided an improved constant
flow smooth jerk-free hydrostatic steering system, using lever operated steering
valve and, use of excess flow to secondary operations with smooth switching,
generally being used in pick and carry type of cranes

-4-
According to another embodiment the oil from the pump enters the valve
and gets divided at flow control valve (1). The controlled oil goes to steering
control valve (3). The excess flow is diverted for main hydraulics. In the neutral
state, the steering oil and excess oil get joined at junction above steering control
valve and all oil is used for main hydraulic function.
Further according to present invention steering control valve (3) diverts
the oil to steering cylinder for left or right turn of vehicle. The metering notches
on the spool allows smooth flow to steering cylinder and also a smooth
switching of oil from steering valve to main hydraulic.
At the outset of the description which follows, it is to be understood that
the ensuring description only illustrates a particular form of its invention.
However, such a particular form is only an exemplary embodiment and without
intending to be understood as an exemplary embodiment and teaching of the
invention and not intended to be taken restrictively.
The nature of the invention, its objective and further advantages residing
in the same will be apparent from the following description made with reference
to the non-limiting exemplary embodiment of the invention represented in the
accompanying informal drawing.
Figure 1 shows the improved constant flow smooth jerk-free hydrostatic
steering system, using lever operated steering valve and. use of excess flow to
secondary operations with smooth switching, generally being used in pick and
carry type of cranes.

-5-
As shown in the Figure 1, the oil from the pump enters the valve and gets
divided at flow control valve (1). The controlled oil goes to steering control
valve (3). The excess flow is diverted for main hydraulics. In the neutral state,
the steering oil and excess oil get joined at junction above steering control valve
and all oil is used for main hydraulic function.
The steering control valve (3) diverts the oil to steering cylinder for left
or right turn of vehicle. The metering notches on the spool allows smooth flow
to steering cylinder and also a smooth switching of oil from steering valve to
main hydraulic.
The internal passage in steering control valve allows use of a single relief
valve (2) for protection while left or right steer of vehicle. A check valve (4) is
used for avoiding main hydraulic back pressures on steering valve.
We shall now describe the present invention with reference to
accompanying to Fig. 1 which is given by way of illustration but does not
restrict the scope of present invention.
In the said Fig. 1, pressure compensated Flow Control is denoted by
numeral 1, steering system relief valve is denoted by numeral 2, steering control
valve is denoted by numeral 3 and check valve is denoted by numeral 4 and the
manner in which different components are interconnected are shown in the said
Fig. 1.

-6-
The invention as described characterizes the improved constant flow
smooth jerk-free hydrostatic steering system, using lever operated steering valve
and, use of excess flow to secondary operations with smooth switching,
generally being used in pick and carry type of cranes.