Planetary Bone Cement Mixer for High-Viscosity Shear Mixing
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Solution Overview
Problem
Existing mixing apparatuses are inadequate for handling highly viscous materials like bone cement, which experience increased viscosity during polymerization, leading to insufficient shear force and inefficient mixing, especially in small batches.
Innovation Solution
A mixing apparatus featuring a stationary circumferential gear driving a planetary mixing element, with a central mixing element, designed to produce a desired shear force through varying gear ratios, surface roughness, and relative velocities, along with a wiping element for efficient material transfer and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional mixing apparatuses are used for highly viscous materials, then the mixing time increases, but the mixing efficiency and homogeneity deteriorate due to insufficient shear force
Solution Approach 1:
The planetary mixing element combines two motion modes: rotation on its own axis and revolution around the central mixing element. This dynamic compound motion creates varying shear forces throughout the mixing well, ensuring effective mixing of highly viscous materials without increasing mixing time. The planetary element's dual motion trajectory continuously changes the mixing paths and contact points, maintaining high mixing efficiency.
Solution Approach 2:
The mixing action is divided into two independent but coordinated components: the central mixing element providing primary rotation and the planetary mixing element providing secondary revolution and rotation. This segmentation of mixing functions allows each element to contribute differently to the overall mixing process, with the planetary element specifically addressing the high viscosity challenge through its orbital motion that reaches all regions of the mixing well.
2Force
If the viscosity of the mixture increases during polymerization, then the resistance to mixing increases, but the available shear force from conventional mixers decreases
Solution Approach 1:
The planetary mixing element's compound motion (rotation plus revolution) dynamically adapts to varying viscosity conditions. As the mixture viscosity increases during polymerization, the planetary element's orbital motion around the central element creates continuously changing shear paths and forces, maintaining effective mixing action despite the increasing resistance. The mechanical advantage of the planetary gear system also amplifies the torque available for high-viscosity mixing.
Solution Approach 2:
The system merges the mixing actions of two elements: the central mixing element and the planetary mixing element. Their combined motions create a synergistic effect where the planetary element's revolution around the central element generates additional shear forces that complement the central element's rotation, providing sufficient total shear force to overcome the increasing mixing resistance during polymerization.
3Adaptability or versatility
If mixing equipment is designed for liquid polymerization mixtures, then the device complexity is reduced, but the adaptability to highly viscous cements deteriorates
Solution Approach 1:
The planetary mixing mechanism introduces dynamic compound motion that is specifically adapted for highly viscous materials. The planetary element's ability to both rotate on its axis and revolve around the central element provides versatility in handling materials across a wide viscosity range, from liquid to highly viscous cement, while the mechanical design maintains reasonable complexity through standardized gear and bearing components.
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 effective mixing of highly viscous materials with viscosities up to 500 Pascal/second within 90 seconds, ensuring complete mixing and efficient transfer of bone cement in small batches, even after the liquid phase has disappeared, by generating sufficient shear force and utilizing a wiping mechanism for material retention and transfer.
Implementation Method 1
designed to produce a desired shear force through varying gear ratios, surface roughness, and relative velocities
Data Source
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AI summary
A mixing apparatus (200) is disclosed which comprises a) a mixing well (252) characterized by an internal volume not exceeding 100 ml.; b) a drive mechanism including a stationary circumferential gear (254) on an inner surface of the mixing well; c) a planetary mixing element (240) driven by a mixing element gear (270) which engages the stationary circumferential gear; and d) a central mixing element (230) positioned substantially at a center of the mixing well; wherein the planetary mixing element revolves around the central mixing element.