FIELD OF INVENTION:
The present invention relates to an improved combined charge pump generally
the invention relates to a hydraulic system, and more particularly, to a method
and apparatus for controlling steering & Transmission all together using
hydraulic fluid system in a construction industry vehicle.
BACKGROUND OF INVENTION:
The charge pump is used to lubricate the internal transmission parts and to
provide forward & reverse functions. It takes input power from the torque
converter. For the purpose of steering control, the input power is taken from
main external pump through the priority valve.
SUMMARY OF THE INVENTION:
Therefore, in view of cost reduction & increase hydraulic system efficiency, the
main objective of the present invention is to combine the steering &
transmission system using a single pump. Here transmission oil is used for both
the application steering & Transmission.
Here steering control will get power from external pump without priority valve.
The present invention relates to, cost reduction & increase hydraulic efficiency
for construction industry vehicle, for example a Back Hoe Loader, having a
control system of, transmission forward & reverse direction .
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
We shall now describe the invention with reference to accompanying drawings
which are given for the sake of illustration, but do not restrict the scope of
present invention.

Referring to figure:-
FIG. 1 is a block diagram of the new control circuit system showing an
embodiment of the present invention, where (1) is Pump (2) is Steering Valve
without Priority, (3) is Transmission Filter (4) is Main Shaft Lubrication
orifice,(5) is Main Line pressure maintenance valve ,(6) is Converter relief
Valve, (7) is Converter pressure maintenance valve, (8) is Torque Converter ,(9)
is cooler (10) is Direction control valve,(l 1) is Main shaft,
DETATILED DESCRIPTION OF THE PRESENT INVENTION:
According to present invention there is provided an improved combined charge
pump comprises of (1) is Pump (2) is Steering Valve without Priority (3) is
Transmission Filter (4) is Main Shaft Lubrication orifice (5) is Main Line
pressure maintenance valve (6) is Converter relief Valve, (7) is Converter
pressure maintenance valve (8) is Torque Converter (9) is cooler (10) is
Direction control valve (11) is Main shaft.
Pump power is taken from engine PTO.
Flow is going through the steering unit & steering return line going to the
transmission.
There is cost reduction in construction machine. Also, with the present
invention there is a provision for conceptual design involvement leading to the
present improved cost efficient steering & transmission system.

Transmission require low pressure to change the forward & reverse direction of
transmission rotation. Hence, the steering tank flow are used for transmission.
Note that,
Pump power is taken from engine PTO.
Flow is going through the steering unit & steering return line
going to the transmission.

WE CLAIM:
1. An improved combined charge pump comprises of (1) is Pump (2) is
Steering Valve without Priority (3) is Transmission Filter (4) is Main Shaft
Lubrication orifice (5) is Main Line pressure maintenance valve (6) is Converter
relief Valve (7) is Converter pressure maintenance valve (8) is Torque
Converter (9) is cooler (10) is Direction control valve (11) is Main shaft.
2. An improved combined charge pump as claimed in claim 1, wherein
Pump power is taken from engine PTO.
3. An improved combined charge pump as claimed in claim 1, wherein
Flow is going through the steering unit & steering return line going to the
transmission.