Hydraulic Bypass Circuit for Fast Cot Retraction and Manual Backup
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Solution Overview
Problem
Existing hydraulic circuits in patient handling apparatuses face challenges in quickly and smoothly moving components, such as the base of an emergency cot, and lack an effective backup system for operation during power outages.
Innovation Solution
The hydraulic circuit includes a pump bypass circuit and a manual bypass circuit, allowing for faster retraction of the hydraulic cylinder and enabling manual operation during power outages by bypassing the pump and maintaining fluid communication between the hydraulic cylinder and the fluid reservoir.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the hydraulic circuit uses electrically controlled valves and a pump to raise or lower the base, then the operation can be automated and controlled, but during power outages the hydraulic cylinder cannot be operated and the base cannot be raised or lowered
Solution Approach 1:
The hydraulic circuit is segmented into two independent pathways: an automated pathway with electrically controlled valves for normal operation, and a manual bypass pathway for emergency operation. This segmentation allows the system to maintain reliability during power outages by switching to the manual pathway when the automated pathway becomes inoperative.
Solution Approach 2:
The system changes its operational parameter from automated valve control to manual bypass operation when power is lost. The manual bypass circuit allows direct manual operation of the hydraulic cylinder, changing the control mode from electrical to mechanical to ensure continued functionality during power outages.
2Stress or pressure
If the hydraulic circuit operates at normal speed through the pump, then the system maintains stable pressure control, but the base cannot be raised or lowered quickly when needed
Solution Approach 1:
The hydraulic circuit dynamically switches between two operational modes: normal mode through the pump for stable pressure control, and emergency mode through the bypass circuit for rapid movement. This dynamic switching allows the system to adapt its speed and pressure characteristics based on operational requirements.
Solution Approach 2:
The bypass circuit enables the hydraulic fluid to skip through the pump and flow directly to the hydraulic cylinder, rushing through the system at high speed. This allows rapid raising or lowering of the base when needed, sacrificing some pressure control stability for speed.
3Speed
If the hydraulic cylinder moves quickly by bypassing the pump, then the retraction speed increases and the base can be raised faster, but significant pressure drops occur which could result in sudden motion of the cylinder
Solution Approach 1:
A control valve is introduced as an intermediary component in the bypass circuit to regulate the flow of hydraulic fluid. This intermediary allows the system to achieve high retraction speed by bypassing the pump while simultaneously controlling pressure drops to prevent sudden, uncontrolled cylinder motion.
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 solution enables quick and smooth movement of the hydraulic cylinder, ensuring efficient loading and unloading of patients, and provides a reliable backup system for manual operation during power outages.
Implementation Method 1
a pump and a hydraulic cylinder operable to selectively raise or lower the patient support surface or the base. The hydraulic circuit is operable to control the flow of hydraulic fluid between the hydraulic cylinder and the fluid reservoir
Implementation Method 2
the bypass circuit is configured to selectively open the control valve to allow fluid to be directed from the cap end chamber to the reservoir to bypass the pump. The bypass circuit provides faster evacuation of the hydraulic fluid from the cylinder
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.