Pneumatic Paste Application Device for Bone Cement
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Solution Overview
Problem
Existing paste application devices for polymethylmethacrylate bone cements are cumbersome, expensive, and impractical for medical use due to reliance on external energy sources, potential for gas leakage, and the need for complex components, making them unsuitable for single-use, hygienic applications in surgical settings.
Innovation Solution
A manually operable paste application device using a two-component cartridge with axially mobile plungers and a pressure vessel made of high-strength materials, powered by a compressed gas cartridge, which allows for efficient mixing and dispensing of viscous pastes without external energy sources, minimizing leakage risks and maintaining structural integrity under high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If electrically-driven extrusion devices are used to extrude thick viscous masses, then the extrusion force is very large, but the device becomes expensive due to non-ferrous metals in motors and requires battery stock or cable connection
Solution Approach 1:
The patent replaces electrical motors with a pneumatic system using a compressed gas cartridge (containing liquid CO2) that expands to drive a plunger mechanism. This pneumatic approach provides sufficient extrusion force for highly viscous bone cement while eliminating motors, batteries, and cable connections, reducing device complexity and enabling disposable single-use design
2Ease of operation
If compressed gas cartridges are used to power the paste application device, then external energy sources are eliminated, but gas leakage may occur through elastic bellows
Solution Approach 1:
The patent eliminates the bellows component entirely by using a direct plunger design where the plunger moves within a sealed chamber formed by the cartridge and device housing. This removes the potential leakage path through bellows while maintaining the ability to convert compressed gas expansion into linear plunger motion for reliable, leak-free operation
Solution Approach 2:
The patent incorporates a check valve mechanism that prevents backflow of compressed gas and maintains sealing integrity. The valve ensures one-way flow control and prevents gas leakage during plunger retraction or pressure equalization, providing beforehand protection against reliability issues
3Use of energy by moving object
If liquid compressed gas is filled into the receptacle before application, then compressed gas is available for extrusion, but the expansion cooling may make the elastic bellows brittle
Solution Approach 1:
The patent removes the bellows component that is susceptible to temperature-induced brittleness. Instead, it uses a rigid plunger mechanism that converts the expansion force of liquid CO2 directly into linear motion without relying on elastic materials that could fail due to cooling during gas expansion
Solution Approach 2:
The patent employs a composite structure combining the pressure-resistant properties of the metal or high-strength plastic cartridge with the sealing properties of elastomeric O-rings and gaskets. This composite approach maintains reliability under temperature variations by using materials selected for their specific properties rather than relying on a single elastic bellows component
4Device complexity
If manually-operated tilting lever devices are used for extrusion, then the device structure is simple, but very strong forces are required to operate with highly viscous pastes
Solution Approach 1:
The patent uses pneumatic pressure from expanding liquid CO2 to generate the extrusion force needed to push highly viscous bone cement through the dispensing needle. This eliminates the need for manual tilting lever operation while maintaining simple device structure, as the gas expansion provides sufficient force without complex mechanical advantage mechanisms
Solution Approach 2:
The patent changes the source of extrusion force from manual mechanical input to pneumatic pressure input. By utilizing the pressure-volume work of expanding liquid CO2, the system achieves the high forces needed for viscous material extrusion while keeping the mechanical structure simple and the user interface easy to operate
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 device enables efficient, cost-effective, and hygienic dispensing of polymethylmethacrylate bone cement with reduced operational force requirements, preventing gas leakage and maintaining structural integrity under high pressures, thus addressing the limitations of existing technologies.
Implementation Method 1
a compressed gas cartridge ( 30 ) which can be opened by means of a hollow mandrel ( 32 ), whereby the compressed gas cartridge ( 30 ) serves to provide compressed gas
Implementation Method 2
the relaxation of the gas from the compressed gas cartridge ( 30 ) that occurs when the compressed gas is conducted from the compressed gas cartridge ( 30 ) into the hollow cylinder ( 1 ) is associated with an expansion (partial adiabatic expansion), during which the relaxing gas cools down, which in turn cools the surrounding containers and, as a result, the hollow cylinder made of plastic material contracts less strongly than the pressure vessel
Data Source
AI summary
A paste application device stores two starting components, for mixing the starting components to form a paste and for the application of the paste. The comprises a two-component cartridge comprising two cylindrical internal spaces, two feed plungers that can be shifted axially in the internal spaces and limit the internal spaces on a first side of the two-component cartridge, and at least two dispensing openings by means of which the internal spaces are open on a second side of the two-component cartridge that is opposite from the first side, a hollow cylinder that is made of a plastic material and has one front face that is open and one front face that is partially closed, in which is situated an axially mobile plunger that has two pestles attached to it, whereby the pestles are oriented in the direction of the open front face, whereby the open front face of the hollow cylinder is arranged to axially touch against the first side of the two-component cartridge, and whereby the plunger closes in gas-tight manner against the internal walls of the hollow cylinder, whereby the two-component cartridge and the hollow cylinder are arranged in a pressure vessel, whereby the pressure vessel touches against the hollow cylinder or is situated at a distance from the hollow cylinder of at most 0.1 mm.