Hydraulic Stretcher Unlocking Valve for Safe Loaded Lowering
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Solution Overview
Problem
Existing mobile rescue stretcher systems face challenges in ensuring safety during manual operation, particularly when loaded, as the manually operable unlocking valve unit risks causing sudden movement and potential injury to patients, and existing solutions are either ineffective or require excessive space.
Innovation Solution
A compact unlocking valve unit with a control chamber and relief valve system, where the pressure from the hydraulic actuator is connected to a piston element and valve body, allowing manual actuation only up to a predetermined pressure level, preventing unintended fluid flow and ensuring safety by keeping the relief valve closed when loaded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a manually operable unlocking valve unit is provided for direct connection of lifting working space with receiving space for hydraulic fluid, then the operation speed is improved (time saving in emergency medicine), but the safety deteriorates (risk of serious injury to patient during manual actuation when loaded)
Solution Approach 1:
A control chamber with a piston element is introduced as an intermediary between the lifting working space and the unlocking valve unit. The piston element responds to pressure changes in the lifting working space and automatically controls the opening/closing of the relief valve, preventing direct manual actuation when the stretcher is loaded. This intermediary mechanism resolves the contradiction by allowing rapid operation when safe while blocking dangerous manual actuation when loaded.
Solution Approach 2:
The control chamber establishes a feedback loop where the pressure in the lifting working space (indicating loading status) automatically influences the state of the relief valve through the piston element. When pressure exceeds a predetermined level (indicating the stretcher is loaded), the piston element closes the relief valve, preventing further rapid lowering. This feedback mechanism ensures safety while preserving operational speed when appropriate.
2Object-affected harmful factors
If existing approaches are used to prevent unintentional actuation of the unlocking valve unit, then the safety is improved, but the device complexity increases and space requirements increase
Solution Approach 1:
The control chamber with piston element operates autonomously based on the pressure in the lifting working space. It automatically determines when the stretcher is loaded and controls the relief valve accordingly, without requiring external sensors, controllers, or complex mechanical interlocks. This self-service approach prevents unintentional actuation while minimizing additional components and space requirements.
Solution Approach 2:
The invention uses the existing hydraulic pressure in the lifting working space as the control signal for the relief valve. The control chamber translates pressure changes into mechanical motion of the piston element, which directly actuates the relief valve. This pneumatic/hydraulic approach eliminates the need for electrical sensors, motors, or complex mechanical linkages, reducing device complexity and space requirements while maintaining safety.
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 provides a safe and space-efficient mechanism that prevents rapid hydraulic fluid flow when the stretcher is loaded, ensuring patient safety and efficient operation by integrating a mechanical actuation system with a spring element and relief valve, allowing controlled movement without risking patient injury.
Implementation Method 1
the pressure prevailing in the lifting working space of the linear actuator of the hydraulic drive system, which is an indicator of the loading of the patent stretcher, is connected to a control chamber and acts on a piston element arranged therein
Implementation Method 2
A mechanical actuation input of the valve unit acts on the valve body with the interposition of a spring element
Data Source
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AI summary
In a mobile stretcher, in order to change the height position of a patient support mounted on a chassis, the geometry of the chassis is modifiable by means of a hydraulic drive system. The latter comprises a linear actuator, a pressure supply unit, and a receiving space for hydraulic fluid, and it moreover has a manually actuatable unlocking valve unit (14) for the direct connection of a stroke working space of the linear actuator to the receiving space for hydraulic fluid. The unlocking valve unit (14) has a control space (28), which is delimited by a piston element (30) guided movably relative to the housing (21) of the valve unit and which communicates with the stroke attachment (23) communicating with the stroke working space. The piston element (30) is operatively connected here to a valve body (27) which interacts with a valve seat (26) of a relief valve (16) configured between the stroke attachment (23) and a tank attachment (25) communicating with the receiving space (6). Moreover, a mechanical actuation input (35) of the valve unit (14) acts on the valve body (27), with interpositioning of a spring element (40).