Hydraulically Amplified Vacuum Pump for Prosthetic Sockets
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Solution Overview
Problem
Current vacuum suspension systems for prosthetic and orthotic devices face challenges such as the need for repeated cycling to create vacuum, potential leaks, and discomfort due to mechanical pumps' length and impact susceptibility, which affect the stability and efficiency of artificial limb attachment.
Innovation Solution
A hydraulically activated vacuum pump apparatus with a housing and reciprocating pistons, where the first piston has a larger hydraulic surface area than the second piston, creating a pneumatic chamber that efficiently evacuates air with minimal displacement, reducing the overall length change of the artificial limb and enhancing comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical pump is used for vacuum suspension, then the system is durable and resistant to impact forces, but the pump's length reduces the height available for prosthetic foot or other components and may negatively affect gait balance
Solution Approach 1:
The patent implements a nested piston configuration where a first piston is positioned within a second piston, both operating within the same housing. This nesting arrangement allows the pump to achieve effective vacuum generation while minimizing the overall length of the device, as the pistons share the same spatial envelope rather than requiring sequential placement.
Solution Approach 2:
The patent employs a hydraulic coupling mechanism between the two pistons, where movement of the first piston transfers force and motion to the second piston through hydraulic pressure. This allows the system to achieve greater total displacement and vacuum capacity without proportionally increasing the physical length of the pump housing.
2Reliability
If a mechanical pump with large vertical deflection is used, then vacuum can be generated, but the amputee's gait may be negatively unbalanced
Solution Approach 1:
By nesting the first piston within the second piston, the system achieves effective vacuum generation with minimal external deflection. The compact nested structure ensures that the pump's vertical movement is contained within a small space, preventing significant changes in the prosthetic limb's overall length that would disrupt gait balance.
Solution Approach 2:
The patent combines the functions of two pistons into a single integrated housing, where the pistons work together through hydraulic coupling. This merging allows the system to achieve the required vacuum generation capability while keeping the overall device compact and stable, thereby maintaining gait balance.
3Reliability
If vacuum suspension is implemented, then exceptional retention and residual limb volume management are achieved, but the system requires repeated cycling to create vacuum which is frustrating and time consuming
Solution Approach 1:
The patent merges the functionality of two pistons into a single integrated system, where the combined displacement of both pistons generates vacuum more rapidly than a single piston could achieve. The hydraulic coupling ensures that movement of one piston contributes to the overall vacuum generation, reducing the time required to achieve effective vacuum suspension.
Solution Approach 2:
The hydraulic coupling mechanism between the two pistons allows for efficient force and motion transfer, enabling the system to generate vacuum more quickly. The fluid-mediated force transmission ensures that the combined effect of both pistons is maximized, reducing the cycling time required to achieve and maintain vacuum suspension.
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 efficient vacuum generation with minimal displacement of the artificial limb, reducing the time to achieve a desirable vacuum level and minimizing the length change during gait, thus improving comfort and stability for amputees.
Implementation Method 1
the first piston having a first hydraulic surface hydraulically linked to a second hydraulic surface of the second piston, the first hydraulic surface having a greater surface area than the second hydraulic surface, thereby driving displacement of the second piston to a greater displacement than the first piston
Data Source
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Figure 1C
AI summary
Methods and apparatus are disclosed relating to a mechanical vacuum socket pump (100) used to establish a vacuum in a socket of an artificial limb. In one case, the pump includes a housing (102) within which two pistons (104, 106) coaxially reciprocate. A surface of each of the pistons is linked hydraulically, such that driving one piston causes movement of the other piston through a hydraulic chamber. One piston is also linked to a pneumatic chamber such that movement of that piston draws air from a limb socket or expels air to the atmosphere upon movement of the piston's pneumatic surface. The surface area of the hydraulic surface of this piston is significantly less than the surface area of the pneumatic surface, so a small volumetric displacement of hydraulic fluid may cause a large displacement of air. Thus, the pump efficiently pumps air with minimal compression and extension of the pump as a whole.