Fluid-Pressure Actuator Unit With Pilot-Operated Shut-Off Valve
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Solution Overview
Problem
Existing fluid-pressure actuator units for lawn mowers cannot operate in both loaded and unloaded modes due to the operation check valve closing at low discharge pressure, preventing the unloaded mode from being available.
Innovation Solution
A fluid-pressure actuator unit with a pilot-pressure-operated shut-off valve that selectively connects or disconnects the discharge passage between the discharge flow restrictor and the fluid-pressure cylinder, allowing the unit to operate in either loaded or unloaded modes based on pressure differences, enabling the blade assembly to lift and move freely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an operation check valve is used to control fluid flow in the discharge passage, then the valve can close when discharge pressure is low, but this prevents the unloaded mode from being available
Solution Approach 1:
A pilot-pressure-operated shut-off valve is introduced as an intermediary control mechanism. This valve uses pilot pressure from the discharge passage to control the main discharge passage, enabling automatic switching between loaded and unloaded modes based on pump operation status, thus resolving the contradiction between reliable valve operation and operational versatility
2Device complexity
If the operation check valve is structured to close at low discharge pressure, then valve control is simplified, but the fluid-pressure cylinder cannot operate freely in unloaded mode
Solution Approach 1:
The shut-off valve is designed to automatically switch between connected and disconnected states based on the pilot pressure generated during pump operation. When the pump operates, pilot pressure increases and automatically connects the discharge passage; when the pump stops, pilot pressure decreases and automatically disconnects it. This self-service mechanism eliminates the need for manual control while enabling free cylinder movement in unloaded mode
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the fluid-pressure actuator unit to automatically switch between loaded and unloaded modes in response to the fluid-pressure pump's operation, allowing the blade assembly to be lifted and maintained in a lifted position while also freely moving up/down in response to external forces without manual intervention.
Implementation Method 1
a discharge flow restrictor provided in the discharge passage... configured to selectively assume the connecting position or the shut-off position in response to a pressure in the discharge passage
Implementation Method 2
a fluid-pressure pump comprising a discharge port and a suction port, which is driven by the electric motor to pressurize a working fluid suctioned via the suction port and discharge the working fluid into the discharge port in a pressurized state
Data Source
AI summary
A fluid-pressure pump 2 rotated by an electric motor 9 drives a fluid-pressure cylinder 3. A discharge flow restrictor 15 is provided in a discharge passage 12 through which a working fluid from the fluid-pressure pump 2 is supplied to fluid-pressure cylinder 3. A pilot-pressure-operated shut-off valve 4 changes over a connecting position A at which the discharge passage 12 between the discharge flow restrictor 15 and the fluid-pressure cylinder 3 is connected to the tank 10 and a shut-off position B at which the discharge passage 12 is disconnected from the tank 10, in response to a pressure P1 in the discharge passage 12 between the discharge flow restrictor 15 and the discharge port 24, thereby enabling a change-over between a loaded mode and an unloaded mode assumed at an fluid-pressure actuator unit 1 in response to an operation of the fluid-pressure pump 2.