Hydraulic Pump Reverse Flow Pressure Relief
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Solution Overview
Problem
Hydraulic systems with highly restrictive flow paths, such as those using gear pumps, often remain pressurized after shutdown, posing hazards during maintenance as rapid pressure relief can cause injury or equipment damage, and there is a need for a method to safely depressurize these systems without requiring the engine to be operating.
Innovation Solution
A method involving a controllably operable valve that allows pressurized fluid to gradually drain back to the reservoir, using a pump as a restrictive flow path, with automatic control by a programmable controller to manage the valve operation and ensure safe pressure relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a highly restrictive flow path pump (e.g., gear pump) is used to pressurize the hydraulic system, then the system can achieve high pressure for heavy lifting, but the system remains pressurized after shutdown with no safe means to relieve pressure
Solution Approach 1:
The pump's restrictive flow path acts as an intermediary component to gradually relieve pressure. By routing fluid through the pump's internal geometry (gears, housing clearances), pressure is reduced controllably without requiring additional relief valves or manual operations, making the system safe for maintenance while preserving high-pressure capability during operation
Solution Approach 2:
The pump serves dual functions: pressurizing the system during operation and gradually relieving pressure during shutdown. The same restrictive flow path that creates high pressure during operation automatically provides controlled pressure relief when the pump is stopped, eliminating the need for separate pressure relief mechanisms
2Loss of time
If pressure is relieved rapidly from the hydraulic system, then pressure is quickly reduced, but sudden movement of work elements (e.g., header dropping) and injury hazards occur
Solution Approach 1:
The pump's restrictive flow path serves as a flow control intermediary that limits the rate of fluid discharge during pressure relief. The internal geometry of the pump (gear clearances, housing restrictions) naturally throttles the flow, ensuring pressure decreases gradually rather than rapidly, preventing sudden component movement while still achieving pressure relief
Solution Approach 2:
The system transitions from a static pressure relief approach (fixed relief valves) to a dynamic approach where the pump's rotation speed and flow characteristics automatically adjust the pressure relief rate. The pump's mechanical design inherently provides dynamic flow restriction that adapts to system conditions, ensuring controlled pressure reduction
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
This method safely reduces hydraulic pressure in work machines like agricultural harvesters, preventing sudden component lowering or injury by gradually relieving pressure without engine operation, ensuring safe system opening and maintenance.
Implementation Method 1
a pump providing a highly restrictive flow path, such as, but not limited to, a gear pump
Data Source
AI summary
A method of gradually relieving pressure in a hydraulic system of a work machine, wherein a pump in fluid communication with the hydraulic system and a fluid reservoir, is operable for pressurizing fluid from the reservoir and pumping the pressurized fluid into the hydraulic system, wherein the pump is restrictive to fluid flow therethrough when not operating, and the hydraulic system includes at least one valve in fluid communication with the work element configured for receiving the pressurized fluid. The valve is controllably operable in at least two operating modes, including a first mode wherein the pressurized fluid can pass therethrough between the pump and the work element or elements, and a second mode wherein the fluid is prevented from passing between the pump and the work element. The method includes operating the valve or valves in the first mode for at least a predetermined time period while the pump is not operating, to allow at least some of any of the pressurized fluid in the work element to flow through the hydraulic system and gradually drain through the pump to the reservoir so as to reduce any pressure in the hydraulic system and the work element.