Meterless Hydraulic Pump Protection via Check Valves
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Solution Overview
Problem
Conventional hydraulic systems face inefficiencies due to flow losses from fluid restriction, and closed-loop systems like the '625 patent are prone to pump failure from shock-loading without adequate protection.
Innovation Solution
A hydraulic system with a pump having variable displacement and over-center functionality, featuring first and second passages with check valves and bypass lines to prevent reverse flow and control fluid flow, along with a control valve to manage bypass lines, creating a closed-loop circuit for efficient operation and pump protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional hydraulic systems use fluid restriction to control actuator speed, then actuator speed can be independently controlled, but flow losses occur that reduce overall system efficiency
Solution Approach 1:
The patent removes the throttling restriction elements from the hydraulic system by implementing a meterless closed-loop circuit. The actuator speed is controlled by varying the pump displacement rather than restricting fluid flow, thereby eliminating the energy losses associated with fluid throttling while maintaining independent actuator speed control capability
Solution Approach 2:
The patent replaces the mechanical fluid restriction method with a pump displacement control mechanism. Instead of using throttling valves to control actuator speed, the system varies the pump's displacement to match the actuator's speed requirements, substituting a more efficient mechanical control method that eliminates flow losses
2Loss of energy
If closed-loop hydraulic systems are used to improve efficiency, then actuator speed is controlled through pump operation without throttling, but the system becomes prone to pump failure from shock-loading
Solution Approach 1:
The patent introduces check valves as intermediary protective elements in the closed-loop hydraulic circuit. These check valves are strategically positioned to prevent reverse flow of pressurized fluid back to the pump, thereby acting as mediators that protect the pump from shock-loading while maintaining the efficiency benefits of the meterless closed-loop system
Solution Approach 2:
The patent implements protective measures in advance by installing check valves before shock-loading can occur. The check valves are pre-positioned in the circuit to automatically prevent reverse flow and cushion against pressure spikes before they can reach and damage the pump, ensuring reliability without compromising the efficient meterless operation
3Reliability
If check valves are added to prevent reverse flow and protect the pump, then pump reliability improves, but system complexity increases
Solution Approach 1:
The patent designs the check valves to serve multiple functions: they primarily protect the pump from shock-loading by preventing reverse flow, but also maintain the closed-loop circuit integrity and support the meterless operation. This multi-functionality reduces the need for additional separate protective devices, thereby limiting the increase in system complexity while achieving reliable pump protection
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
The system enhances efficiency by controlling actuator speed through pump operation rather than fluid restriction and protects the pump from shock-loading, improving overall hydraulic system performance and reliability.
Implementation Method 1
a first check valve disposed within the first passage to allow fluid flow only from the pump to the actuator, and a second check valve disposed within the second passage to allow fluid flow only from the pump to the actuator
Implementation Method 2
A meterless hydraulic system generally includes a pump connected in closed-loop fashion to a single actuator or to a pair of actuators operating in tandem. During operation, the pump draws fluid from one chamber of the actuator(s) and immediately discharges pressurized fluid back into an opposing chamber of the same actuator(s)
Implementation Method 3
a first bypass line connecting the first passage at a location between the actuator and the first check valve to the first passage at a location between the first check valve and the pump, and a second bypass line connecting the second passage at a location between the actuator and the second check valve to the second passage at a location between the second check valve and the pump
Data Source
AI summary
A hydraulic system is disclosed. The hydraulic system may have an over-center, variable-displacement pump, an actuator, and first and second passages that create a closed-loop circuit. The hydraulic system may also have first and second check valves disposed in the first and second passages, respectively, to allow flow only from the pump to the actuator. The hydraulic system may further have a first bypass line connecting the first passage at a location between the actuator and the first check valve to the first passage at a location between the first check valve and the pump, and a second bypass line connecting the second passage at a location between the actuator and the second check valve to the second passage at a location between the second check valve and the pump. The hydraulic system may additionally have a valve configured to control flow through the first and second bypass lines.