Membrane Pneumatic Drive for Frictionless Motion Control
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Solution Overview
Problem
Existing motor-driven and pneumatic drive devices for medical instruments face challenges in minimally invasive surgery due to space constraints, sterility issues, and non-proportional force transmission, leading to control inaccuracies and safety risks.
Innovation Solution
A pneumatic drive device with a gas-tight membrane surrounding the pressure chamber and a piston that moves almost frictionlessly, allowing precise control of translational and rotational movements through proportional pressure application, using membranes made of thermoplastic elastomer and optional coatings for reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piston is directly mounted in a cylinder to form a pressure chamber, then gas-tightness is improved, but friction between piston and cylinder increases causing stick-slip effect and non-proportional movement
Solution Approach 1:
The system is divided into two separate functional components: a piston that moves freely without direct mounting to the cylinder, and a membrane that provides gas-tight sealing. This segmentation allows the piston to move without friction while the membrane maintains pressure chamber integrity.
Solution Approach 2:
A membrane is introduced as an intermediary element between the piston and the cylinder wall. The membrane provides the gas-tight seal without requiring direct contact between the piston and cylinder, thereby eliminating friction and stick-slip effects while maintaining pressure containment.
2Reliability
If a piston is directly mounted in a cylinder to ensure gas-tightness, then sealing is improved, but friction causes loss of applied force and affects controllability
Solution Approach 1:
The sealing function is separated from the moving piston component and assigned to a dedicated membrane. This allows the piston to move freely without frictional losses while the membrane maintains the pressure differential necessary for actuation.
Solution Approach 2:
The membrane acts as an intermediary that transmits pressure forces without requiring direct mechanical contact between the piston and cylinder wall, thereby eliminating frictional energy losses while maintaining sealing integrity.
3Ease of operation
If an electric motor is used to drive the instrument, then precise control is achieved, but spatial requirements increase and sterility issues arise
Solution Approach 1:
The electric motor is replaced with a pneumatic actuation system that uses pressurized gas to directly move the piston and actuator shaft. This substitution eliminates the need for bulky motor housing and complex transmission mechanisms, reducing spatial requirements while maintaining control precision through direct force application.
4Volume of stationary object
If an electric motor is directly coupled to the instrument for direct drive, then space is reduced, but power supply and sterility problems worsen
Solution Approach 1:
The electric motor is replaced with a pneumatic system that uses gas pressure for actuation. This eliminates the need for electrical power supply to the sterile field and removes sterility concerns associated with electric motors, while the direct pneumatic actuation maintains compact dimensions.
5Force
If a gearbox is used to transmit motor movement to the instrument, then force amplification is achieved, but force proportionality to movement is lost due to gearbox losses
Solution Approach 1:
The gearbox is replaced with a direct pneumatic actuation system where pressurized gas directly moves the piston and actuator shaft. This eliminates mechanical transmission losses and ensures that the applied gas pressure is directly proportional to the resulting movement, while still achieving sufficient force through the pneumatic pressure itself.
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
Ensures precise, proportional, and loss-free movement control of medical instruments, enhancing safety and sterility by minimizing friction and leakage, and allowing continuous regulation of force and position.
Implementation Method 1
The membrane is capable of being deflected axially in a circumferential region of the membrane by pressurizing the pressure chamber
Implementation Method 2
the membrane should be designed in such a way that the reversible expansion/deflection of the membrane is possible, which can be achieved, for example, by a suitable choice of material, in particular with a high elasticity
Data Source
AI summary
A pneumatic drive device includes a housing, a piston, and a first membrane. The first membrane and the piston are coupled to each other in such a way that an axial movement of the first membrane, caused by pressurizing a first pressure chamber, is converted into a translational movement of the piston. The pneumatic drive device also includes an output element, and a membrane. The membrane and the output element are coupled to each other in such a way that a circumferentially section-wise oscillating axial movement of the membrane, caused by circumferentially successive pressurization and depressurization of respective pressure chambers, is converted into a rotational movement of the output element.