Closed Hydraulic Circuit for Stretcher Positioning Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hydraulic drive units for stretchers suffer from air being sucked into the system when the differential cylinder is extended, leading to reduced operating pressure and inaccurate positioning, which can pose safety risks for patients and operators.
Innovation Solution
A hydraulic drive unit with a tank that has a variable volume, separated from the atmosphere, ensuring a closed hydraulic circuit. This configuration prevents air from being drawn into the system and prevents oil from leaking, regardless of the stretcher's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid tank under atmospheric pressure is used, then the tank structure is simple, but air is sucked into the hydraulic circuit when the differential cylinder is extended
Solution Approach 1:
The patent employs a flexible membrane to create a variable volume tank that can expand and contract as oil moves between the differential cylinder and the tank. This flexible structure replaces rigid atmospheric tanks, preventing air from entering the hydraulic circuit while accommodating volume changes during cylinder extension and retraction.
Solution Approach 2:
The tank's volume parameter is made variable through the flexible membrane design, allowing it to dynamically adjust its capacity as oil is displaced during differential cylinder operation. This parameter change enables the tank to maintain a closed hydraulic system without requiring a rigid atmospheric structure.
2Reliability
If the tank is positioned to prevent air suction, then air intake is prevented, but the system cannot adapt to different stretcher positions
Solution Approach 1:
The patent transforms the static rigid tank into a dynamic variable volume tank using a flexible membrane. This dynamic structure automatically adapts to different stretcher positions by adjusting its volume as oil moves, maintaining the closed hydraulic circuit integrity regardless of the system's orientation or position during operation.
3Reliability
If a fixed volume tank is used, then the tank design is simple, but oil leaks from the drive unit in certain positions
Solution Approach 1:
The flexible membrane forming the variable volume tank prevents oil leakage by dynamically accommodating volume changes. As the differential cylinder extends or retracts, the membrane expands or contracts accordingly, maintaining sealed connections and preventing oil from leaking in various positions, unlike fixed volume tanks that cannot adapt to position changes.
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 solution ensures that only oil is drawn by the pump, maintaining operating pressure and allowing for precise positioning of the differential cylinder, thereby enhancing safety for both patients and operators.
Implementation Method 1
the tank is a flexible tank and in particular comprises a flexible membrane
Data Source
AI summary
A hydraulic drive unit for a stretcher has a hydraulic circuit with a differential cylinder, a pump, a tank and a valve assembly. The differential cylinder includes a rod working chamber and a piston working chamber. The valve assembly is switchable into at least a first state and a second state, wherein the rod working chamber is connected to the tank in the first state and to the pump in the second state, and wherein the piston working chamber is connected to the pump in the first state and to the tank in the second state. The tank is a tank separated from the atmosphere with a variable tank volume, so that the hydraulic circuit is configured as a closed hydraulic circuit. A stretcher having such a hydraulic drive unit is also provided.