Membrane Pneumatic Drive for Stick-Slip-Free Sealed Motion
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Solution Overview
Problem
Existing drive devices for medical instruments face challenges with friction, leakage, and inefficient force transmission, particularly in minimally invasive surgery, with electric motors, and pneumatic devices experiencing stick-slip effects and sterility issues.
Innovation Solution
A pneumatic drive device with a membrane that surrounds the pressure chamber, allowing the piston to move almost frictionlessly and proportionally to applied pressure, using thermoplastic elastomer membranes and position sensors for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piston is mounted in a cylinder to form a pressure chamber, then the pressure chamber can be sealed, but friction occurs between the piston and cylinder causing the stick-slip effect
Solution Approach 1:
A membrane is introduced as an intermediary element to replace the traditional piston-cylinder contact system. The membrane forms the pressure chamber boundary without requiring friction-based sealing, eliminating the stick-slip effect while maintaining pressure containment.
Solution Approach 2:
The mechanical piston-cylinder system with contact-based sealing is replaced by a membrane-based pressure chamber. This substitution eliminates the need for friction-based sealing mechanisms while achieving the same pressure containment function.
2Power
If an electric motor is used to drive the instrument, then sufficient driving force can be provided, but the motor cannot be made sterile and requires complex power supply
Solution Approach 1:
The electric motor is replaced by a pneumatic drive system using compressed gas. This eliminates the need for electrical power supply and associated sterility issues, while providing sufficient driving force through gas pressure acting on the membrane.
3Ease of operation
If a gearbox is used to transmit motor movement, then the instrument can be driven, but force transmission is not proportional due to losses
Solution Approach 1:
The gearbox mechanism is replaced by direct pneumatic actuation of the membrane. This eliminates mechanical transmission losses and ensures proportional force transmission from the driving gas to the instrument movement.
4Productivity
If a piston is used in a pneumatic drive device, then movement can be generated, but leakage occurs between piston and cylinder compromising patient safety
Solution Approach 1:
The membrane serves as an intermediary that contains the compressed gas without requiring contact-based sealing. This eliminates leakage paths that could allow compressed air to escape near the patient while maintaining pressure for movement generation.
Solution Approach 2:
A flexible membrane is used to form the pressure chamber boundary. This thin film structure provides effective sealing without the leakage issues associated with rigid piston-cylinder interfaces, ensuring patient 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
Ensures precise, proportional, and almost loss-free movement of the actuator shaft, addressing sterility and stick-slip effects, and enabling precise control of translational and rotational movements.
Implementation Method 1
By increasing the pressure in the pressure chamber, the membrane is caused to expand and to deflect axially
Implementation Method 2
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
Implementation Method 3
the expansion of the membrane causes the piston to move along the longitudinal direction of the piston by pushing the piston
Data Source
Figure 1~3
Figure 4~6
AI summary
The disclosure is directed to a pneumatic drive device (2), comprising a housing (4), a piston (6), and a first membrane (8), the first membrane (8) and the piston (6) being coupled to each other in such a way that an axial movement of the first membrane (8), caused by pressurizing a first pressure chamber (16), is converted into a translational movement of the piston (6). Further, the disclosure is directed to a housing (54), an output element (56), and a membrane (58), the membrane (58) and the output element (56) being coupled to each other in such a way that a circumferentially section- wise oscillating axial movement of the membrane (58), caused by circumferentially successive pressurization and depressurization of respective pressure chambers (66, 68, 70), is converted into a rotational movement of the output element (56).