Due to the structure of the displacement limit, it is generally considered gear pump can only be used as a constant flow hydraulic source. However, the attachment-threaded coupling valve scheme is effective in increasing its functionality, reducing system costs and increasing system reliability. As a result, gear pump performance can approach the costly and complex piston pump.
For example, the direct installation of the control valve on the pump eliminates the need for piping between the pump and the direction, thus controlling the cost. Less fittings and connectors reduce leakage and improve operational reliability. And the pump itself to install the valve can reduce the cycle pressure of the circuit, improve its performance. Here are some of the loops that can enhance the basic functions of a gear pump, some of which are practically proven viable circuits, while others are innovative.
Uninstall the circuit
The unloading element will combine the high flow pump with the low power single pump. Liquid is discharged from the outlets of the two pumps to achieve a predetermined pressure and / or flow rate. At this point, the high-flow pump circulates the flow from its outlet to the inlet, reducing the pump's output flow to the system by reducing the magnetic power slightly above the desired value for high-pressure operation. The percentage of flow reduction depends on the ratio of the unloaded displacement to the total displacement at this time, and the combination or threaded unloading valve reduces or even eliminates the piping, apertures and accessories and other possible leaks.
The easiest to uninstall components by hand. The spring causes the unloader valve to be switched on or off, and when the valve is manipulated, the on-off condition of the valve is switched. Lever or other mechanical mechanism is the easiest way to manipulate this valve.
The pilot (pneumatic or hydraulic) unloader valve is an improvement on the way in which the valve can be remotely controlled. The biggest progress is the use of electrical or electronic control of the solenoid valve, which can be used not only remote control, and can be automatically controlled by the computer, it is generally considered that this simple uninstall technology is the best case.
Manually operated, unloaded components are commonly used in circuits that require high flow rates and rapid operation for rapid operation, high flow rates, and reduced flow for precise control, such as fast telescopic boom circuits. Circuit unloading signal without the role of manipulation, the circuit has been a large output flow. For normally open valves, the circuit will output a small flow under normal conditions. Pressure sensing unloading is the most common program. The spring action puts the unloader valve in its high flow position. When the circuit pressure reaches the preset value of the relief valve, the relief valve opens and the relief valve switches to its low flow position under hydraulic pressure and under action. Pressure sensing unloading valve is basically an unloading system to achieve the pressure relief unloading components, commonly used in the splitter and hydraulic vise jaw.
The unloading valve in the flow sensing unloading circuit is also urged by the spring to a large flow rate. The size of the fixed orifice in the valve is based on the required flow rate for the machine's optimum engine speed. If the engine speed exceeds this optimum range, the orifice pressure drop will increase, displacing the unloader valve to the low flow position. As a result, adjacent components of the high-flow pump are dimensioned to throttle the maximum flow rate. Therefore, the circuit consumes less energy, operates smoothly and costs less. A typical application of this circuit is to limit the loop flow to the optimum range to improve the overall system performance or to limit the circuit pressure during high speed operation of the machine. Commonly used in garbage truck and so on.
The unloading valve of the pressure-flow sensing unloading circuit is also spring-biased to the high-flow position, unloading no matter whether the pressure reaches the preset pressure or the flow rate. Equipment in idle or normal working speed can be completed under high-pressure work. This feature reduces unnecessary traffic and therefore reduces the power required. Because of this circuit has a wide range of load and speed changes, it is often used in mining equipment.
A power-sensitive pressure-sensing unloader circuit consisting of two slightly different pressure-sensing off-load pumps, two pumps driven by the same prime mover, each receiving a pilot unload signal from another unload pump. This sensing method is called interactive sensing, which allows one set of pumps to work at high pressure and the other at a high flow rate. Two relief valves can be adjusted for each circuit's special pressure to unload one or two pumps. This program reduces the power requirements, it can be low-cost prime mover.
Priority flow control
Regardless of the speed of the pump, the working pressure or the amount of flow required by the branch, the value of the primary flow control valve always ensures the flow required for the operation of the equipment. Setting a flow valve (proportional valve) will be a combination of control and hydraulic pump, eliminating pipelines and eliminate external leakage, so reduce the cost. A typical application of such a gear pump circuit is the steering mechanism often found on truck cranes, which eliminates the need for a pump.
