Hydraulic-Pneumatic Damper Unit for Supported Knee Motion Reversal
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Solution Overview
Problem
Existing damper units in orthopedic devices, such as prosthetic and orthotic devices, struggle to provide simplified resistance against movement reversal and support during opposite movements, particularly in artificial knee joints, without requiring complex control mechanisms.
Innovation Solution
A damper unit combining a hydraulic cylinder with a displaceable hydraulic piston and a pneumatic cylinder with a displaceable pneumatic piston, where the volume change in hydraulic chambers differs, and the pneumatic chambers are fluidly coupled to a compensating volume, allowing hydraulic damping during braking and pneumatic support during opposite movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a hydraulic damper device is used to provide resistance to movement, then resistance against movement reversal is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent combines a hydraulic damper device and a pneumatic spring device into a single integrated unit. The hydraulic cylinder and pneumatic cylinder share a common piston rod and are arranged in series, allowing both resistance generation and movement support functions to be achieved without separate control mechanisms. This merging eliminates the need for complex control systems while maintaining both force resistance and energy storage capabilities.
Solution Approach 2:
The integrated damper-spring unit performs multiple functions simultaneously: the hydraulic cylinder provides resistance to movement in both directions, while the pneumatic cylinder stores and releases energy to support opposite movements. This multi-functionality is achieved within a single device structure, eliminating the need for separate control mechanisms that would be required if these functions were implemented independently.
2Ease of operation
If a pneumatic spring is added to support opposite movements, then support during movement reversal is improved, but the device complexity increases
Solution Approach 1:
The patent merges the pneumatic spring device with the hydraulic damper device into a single integrated unit. Both cylinders share a common piston rod and are arranged in series along the same axis, allowing the pneumatic spring to support opposite movements without adding separate structural components or control mechanisms. This integration maintains structural simplicity while achieving movement support functionality.
3Device complexity
If hydraulic and pneumatic cylinders are integrated with a common piston rod, then device complexity is reduced, but the volume change in hydraulic chambers becomes unbalanced
Solution Approach 1:
The patent introduces a compensating volume as an intermediary element to balance the hydraulic fluid volume changes. The compensating volume is connected to the hydraulic chambers and contains a compressible gas or spring that absorbs excess fluid volume during piston movement. This intermediary compensating mechanism allows the integrated hydraulic-pneumatic structure to function with unbalanced chamber volumes without compromising system performance.
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 springy bending during stance phase flexion and supports stance phase extension by storing and releasing kinetic energy, providing adjustable resistance and support in opposite directions without complex control efforts, enhancing the physiological movement of artificial knee joints.
Implementation Method 1
The cylinder is filled with a hydraulic fluid which is pumped from the decreasing hydraulic chamber into the increasing hydraulic chamber when the piston moves
Implementation Method 2
The piston rod is coupled to a first component, and the housing or cylinder is coupled to the second component. The cylinder is filled with a hydraulic fluid
Implementation Method 3
A pneumatic cylinder with a displaceably mounted pneumatic piston coupled to the piston rod and dividing the pneumatic cylinder into two pneumatic chambers fluidly connected to one another via at least one pneumatic channel
Implementation Method 4
it is possible to supplement a hydraulically damped movement with a gas spring or a pneumatic spring. During the braking movement of the hydraulic cylinder, it is simultaneously possible to compress the gas volume or the volume of a compressible fluid contained therein in a pneumatic chamber
Implementation Method 5
Throttle devices are provided in the hydraulic channel(s) to increase or adjust the flow resistance. The throttle devices can be adjustable, for example, in the form of control valves or switching valves, so that a variable flow resistance can be provided
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a damper unit (40) comprising: a hydraulic cylinder (50) having a hydraulic piston (51) movably mounted therein, which hydraulic piston is coupled to a piston rod (70) and divides the hydraulic cylinder (50) into two hydraulic chambers (52, 53) which are fluidically interconnected via at least one hydraulic channel (54); and a pneumatic cylinder (60) having a pneumatic piston (61) movably mounted therein, which pneumatic piston is coupled to the piston rod (70) and divides the pneumatic cylinder (60) into two pneumatic chambers (62, 63) which are fluidically interconnected via at least one pneumatic channel (64); wherein the value of the volume change of the hydraulic chambers (52, 53) during a movement of the hydraulic piston (51) is different and the hydraulic chambers (52, 53) are fluidically coupled to an equalisation volume (80).