Hydraulic Drive with Closed Working Fluid Circulation System
New Revolutionary Hydraulic Invention
We are the inventors of a revolutionary new hydraulics system in the field of hydraulics engineering. The invention relates to hydraulic engineering, in particular to hydraulic drive systems which can effectively be used to obtain an energy-saving operation of the sealed hydraulic system.
Currently, closed (or sealed) hydraulic systems are described as:
1. A system with an additional fueling system, to which the fuel pump has an expansion tank, which communicates with the atmosphere
2. A system without the expansion tank, but with a double-rotating hydraulic pump which operates the system reversely, and which spends a large amount of energy when started.
The main drawback of all current hydraulic systems is that they require an expansion tank, which increases the weight, volume, and price of the hydraulic system.
Another disadvantage includes the oxidation of the fluid (oil). Oxidation, or the chemical union of oil and oxygen, is one of the primary causes for decreasing the stability of hydraulic fluid. When the reaction begins, a catalytic effect takes places. The chemical reactions result in formation of acids that can increase the fluid viscosity and can cause corrosion. Polymerization and condensation produce insoluble gum, sludge, and varnish that cause sluggish operation, increase wear, reduce clearances, and plug lines and valves. The biggest contribution to oxidation include temperature, pressure, water, contaminants, metal surfaces, and agitation as well. In addition, even with slight air ingress into the oil, it starts to foam, creating conditions favorable for the formation of air emulsions with very low density. This disturbs the uniformity of movement of the working parts . Dissolved air in the oil disturbs the uniformity of the hydraulic drive motor, influences the viscosity of oil, and decreases the speed of the hydraulic equipment. In accordance with the laws of thermodynamics, when air bubbles compress, they are heated up and transfer heat to the hydraulic fluid. The hydraulic fluid transfers heat to the atmosphere, which as a result significantly lowers the efficiency of hydraulic drive. If there was no gas in the working fluid, the fluid will heat up less.
The Aim of the Invention – The creation of a compact, highly efficient, energy-saving, simple and reliable hydraulic drive unit, providing ample technological and operational capabilities through the implementation of sealed hydraulic machinery which does not have contact with the air.
The Scope of Use- The invention can be widely used in mechanical engineering, machine building, shipbuilding, and aircraft building.
The technical result – An increase in pressure characteristics of the hydraulic drive, which leads to an increase in speed of operation of the machine.
The economic effect – Is achieved by creating an initial overpressure at the fluid inlet in the pump.
Implementation of the hermetically sealed system allows the hydraulic drive to work independently of areal position, regardless of atmospheric pressure and the force of gravity, and also prevents the formation of condensate during the operational process of the hydraulic drive. Moreover, execution of the sealed system allows to deaerate the working fluid after filling the system, as a result of which the working fluid will heat less during operation, and the absence of dissolved air in the working fluid will no longer disturb the uniformity of the hydraulic motor machine.
FIG. 1 shows the diagrammatic view of embodiment of the hydraulic drive unit with a double-acting hydraulic motor with equal areas and volumes of the working chambers, with an initial overpressure in the system, relative to the pressure outside the system. By turning the control lever in either direction, results in the right-and-left movement of the hydraulic drive piston.
Due to the pressure of the piston, when filling a working chamber of the hydraulic cylinder with hydraulic fluid, results in the forced movement of the rod and the working fluid in the opposite direction, causing the working fluid feed to the pump and its continuous operation in a mode corresponding to the achievement of the maximum carrying capacity.
To create and maintain the overpressure in the system, a hydraulic accumulator is installed on the suction line of the pump. Because of the excess pressure, there is a forced feed of fluid to the pump, as a result of which it completely excludes the possibility of pump operation in the cavitation mode and it’s pressure characteristics are increased. The consequence is a significant acceleration of the pumping processes of the fluid, i.e. an increase in the productivity of the working machine as a whole. The initial pressure in the system may be small – between 1.0 – 2.0 atm. and above, depending on the expected productivity of the working machine.
The initial overpressure in the hydraulic accumulator, in excess of the pressure from the outside of the hydraulic accumulator, creates a pressure throughout the whole hydraulic system, and the pump suction line in particular. As a result the pump operates in a series of connection, in which the pressure line of the first pump is connected to the suction line of the second pump, allowing for an overpressure to be created at the suction point of the second pump, so the second pump operates with improved pressure characteristics. According to scientific literature, “through a series of pump connections, the discharges to be skipped by all pumps are equal, and the head pressure is equal to the sum of the head pressures of each individual pumps (G.I. Krivchenko.”Hydraulic Machines”, Moscow, “Energy”, 1978, p.247)”. The series of pump connections is used in practice when you want to get more head pressure than the pump can produce, or when you have a need to modify the head pressure developed by the pump installation.
Therefore, the invented hydraulic drive is capable of creating an operating pressure that provides a greater speed of movement of the hydraulic drive rod, and of the mechanical working member as a whole with stable and significant energy saving.
Due to the volume of fluid in the hydraulic accumulator, or because of the springs tension, if the hydraulic accumulator is of spring-type, there is a control of balance of the working fluid, i.e. the hydraulic accumulator acts as a capacity regulator only in instances of where mechanical wear occurs in the joints (backlashes).
It is also possible to use this hydraulic drive unit for the operation of the rotary hydraulic drives.