Hydraulic Bypass Circuit for Fast Cot Retraction Without Power
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Solution Overview
Problem
The existing hydraulic circuits in patient handling apparatuses, such as emergency cots, face issues with power outages and pressure variations, leading to inefficient movement and manual operation challenges, particularly during loading and unloading processes.
Innovation Solution
A hydraulic circuit with a pump bypass circuit and manual bypass circuit that allows for faster evacuation of hydraulic fluid and manual operation, ensuring smooth motion and quick retraction of the base relative to the frame, even in the absence of power, by utilizing a solenoid valve and accumulator for pressure management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic circuit uses electrically controlled valves and pump for base raising/lowering, then the operation speed and control precision are improved, but the reliability during power outages deteriorates
Solution Approach 1:
The system enables manual operation mode where the operator can directly manipulate the hydraulic circuit components (valves, pump) without electrical assistance. The manual pump and valve mechanisms are designed to be operable by hand, allowing the base to be raised or lowered even when electrical power is unavailable, thus making the system self-sufficient across different operational conditions.
Solution Approach 2:
The hydraulic circuit is designed with dynamic switching capability between electrically controlled mode and manual operation mode. The system can adapt its control mechanism based on power availability, transitioning from automated valve control to manual valve manipulation, and from electric pump to manual pump operation, ensuring continuous functionality under varying conditions.
2Productivity
If the hydraulic circuit operates at high speed for quick loading/unloading, then the productivity is improved, but the pressure stability and motion smoothness deteriorate
Solution Approach 1:
The system incorporates pressure sensing and flow control mechanisms that provide feedback to regulate hydraulic fluid delivery. During high-speed operation, the feedback system monitors pressure variations in the cylinder chambers and adjusts the pump output or valve positioning to maintain pressure stability, preventing sudden motions while preserving overall operational speed.
Solution Approach 2:
The hydraulic circuit employs periodic or pulsed fluid delivery rather than continuous high-flow operation. By delivering hydraulic fluid in controlled pulses or stages, the system achieves quick base movement while allowing pressure to stabilize between pulses, reducing the harmful effects of pressure variations and ensuring smoother motion during high-productivity operations.
3Reliability
If the hydraulic circuit uses manual operation for backup, then the reliability during power outages is improved, but the operation speed and efficiency deteriorate
Solution Approach 1:
The manual operation components are designed to handle partial loads or less demanding operational scenarios. For routine high-speed loading and unloading, the electrically controlled system is used to maintain productivity. The manual system serves as a backup for critical situations where reliability is paramount but speed requirements are reduced, accepting lower productivity as a trade-off for ensuring operation continuity during power outages.
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 quick and efficient movement of the patient handling apparatus components, ensuring rapid loading and unloading while maintaining smooth motion and allowing manual operation during power outages, thus enhancing operational reliability and efficiency.
Implementation Method 1
The pump bypass circuit provides faster evacuation of the hydraulic fluid from the cylinder, such as the cap end chamber of the hydraulic cylinder
Implementation Method 2
utilizing a solenoid valve and accumulator for pressure management
Implementation Method 3
utilizing a solenoid valve and accumulator for pressure management
Data Source
AI summary
A patient handling apparatus includes a patient support surface, a base, and a hydraulic circuit. The hydraulic circuit includes a pump, a fluid reservoir, and a hydraulic cylinder operable to selectively raise or lower the patient support surface or the base. The hydraulic circuit controls flow of fluid between the cylinder and the fluid reservoir to thereby control the movement of the base or patient support surface. In addition, the hydraulic circuit may include a manual bypass circuit configured to bypass the pump in response to a manual input, which allows manual extension or retraction of the cylinder, for example, when the pump is not operational. The hydraulic circuit may also include a pump bypass circuit configured to bypass the pump to allow fluid to discharge from the cap end to the fluid reservoir for faster evacuation of fluid from the cylinder, thereby increasing retraction speed of the rod.