An Improved Hydrostatic Parallel Series Propulsion System

FIELD OF INVENTION: The present invention relates to an improved hydrostatic parallel series propulsion system. Generally the present invention relates to a hydraulic fluid system, and more particularly, to a method and apparatus for controlling a hydraulic fluid system in a construction industry vehicle. BACKGROUND OF INVENTION: It is well known, that in vehicle such as compactors driven by hydrostatic transmission having drive on both drum is generally driven by two fixed or variable motor mostly in parallel configuration or sometime in series. These machines need to satisfy both gradeabilty and speed requirement. In known system the motors are simultaneously driven in parallel. The engine is driven in full speed. The vehicle speed is controlled by changing the displacement of the pump or motor or both. The main disadvantage of such system is that a high capacity pump is used to satisfy speed and gradeability requirement. Another disadvantage is that for the optimization of system the engine has to run at a high RPM. This decreases the life of engine as well results in low system efficiency. The other known system uses motor in series. It reduces the motor size as a result the speed increases but gradeability decreases. However, this

configuration is rarely used. The objective of the present invention is, to optimize the efficiency of the hydraulic system, by using parallel series system. SUMMARY OF THE INVENTION: Therefore, in view of the disadvantages stated above, the main objective of the present invention is to describe a parallel series system which satisfy both speed and gradeability of machine and in turn increase the overall system efficiency. The present invention relates to, an improved hydraulic system for construction machines such as compactors having two motors at front and rear drive which can be witched between parallel and series to attain gradeabilty as well as speedy mounted control. The proposed system will use half the size of motor used in purely parallel system. 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 drawing: The Figure 1 is a block diagram of the new control circuit system showing an embodiment of the present invention, where (1) is a piston pump, (2) is a parallel series switch valve (3) is electric control switch (4) and (5) are propulsion motors. DETATILED DESCRIPTION OF THE PRESENT INVENTION:

According to the present invention there is provided an improved hydrostatic parallel series propulsion system is combination of: (i) parallel flow system used in work mode and attain gradeabilty at low speed; (ii) series flow by switching the conversion valve for high speed travel applications characterized in that (1) is a piston pump, (2) is a parallel series switch valve (3) is electric control switch (4) and (5) are propulsion motors. The oil from engine mounted pump 1 is divided into both front drive motor 4 and rear drive motor 5. Operation of the switch 3 the direction of the valve 2 shifts and oil travels from drive motor 1 to drive motor 2. The combination of above mentioned features make the hydraulic fluid system highly energy efficient and compact. The parallel propulsion system makes the machine achieve the working mode and gradability mode functionalities while the series propulsion system makes the machine work in transport mode with maximum speed. There is provided a parallel series drive circuit for hydrostatic propulsion. As shown Figure 1, the oil from engine mounted pump 1 is divided into both front drive motor 4 and rear drive motor 5. This mode is referred as parallel

mode and is a low speed high torque mode. This is beneficial in work mode and climbing steep slope as per specification. As shown in Figure 2 on operation of the switch 3 the direction of the valve 2 shifts and oil travels from drive motor 1 to drive motor 2. This mode is referred as series mode. The speed of machine will be double than the parallel mode. This is beneficial for fast travel of machine.

WE CLAIM: 1. An improved hydrostatic parallel series propulsion system is combination of: (i) parallel flow system used in work mode and attain gradeabilty at low speed; (iii) series flow by switching the conversion valve for high speed travel applications characterized in that (1) is a piston pump, (2) is a parallel series switch valve (3) is electric control switch (4) and (5) are propulsion motors. 2. An improved hydrostatic parallel series propulsion system as claimed in claim 1, wherein the oil from engine mounted pump 1 is divided into both front drive motor 4 and rear drive motor 5. 3. An improved hydrostatic parallel series propulsion system as claimed in claim 1, wherein operation of the switch 3 the direction of the valve 2 shifts and oil travels from drive motor 1 to drive motor 2. 4. An improved hydrostatic parallel series propulsion as claimed in of claims 1 and 3 wherein the combination of above mentioned features make the hydraulic fluid system highly energy efficient and compact. 5. An improved hydrostatic parallel series propulsion as claimed in of claims 1 to 4, wherein the parallel propulsion system makes the machine achieve the working mode and gradability mode functionalities while the series

propulsion system makes the machine work in transport mode with maximum speed.