Inflatable Elastomeric Pump for Controlled Infusion Flow
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Solution Overview
Problem
Conventional inflatable elastomeric bladders used in intravenous drug delivery systems experience variability in pressure and flow rate, making it difficult to deliver drugs at a controlled rate and often leave residual liquid, due to their design and materials.
Innovation Solution
An improved elastomeric pump design featuring a mandrel with a cylindrical body and an inflatable silicone tube with specific dimensions and Shore Hardness, allowing for uniform expansion and contraction to ensure consistent pressure and flow rates, with a fill volume of 50-600 ml and minimal residual volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inflatable elastomeric bladders are used, then the device can deliver liquid intravenously, but the pressure and flow rate vary widely, making controlled rate delivery difficult
Solution Approach 1:
The patent applies parameter changes by specifying precise dimensional parameters for the bladder (initial volume, maximum volume, wall thickness ratios) and material properties (Shore hardness range) to control the pressure-volume relationship. This ensures that the bladder maintains substantially constant pressure over a significant portion of its volume range, enabling reliable and controllable liquid delivery rates.
Solution Approach 2:
The invention utilizes the dynamic expansion and contraction of the elastomeric bladder in a controlled manner. By designing the bladder to expand from an initial volume to a maximum volume and then contract back, it creates a predictable pressure profile that can be tuned to maintain stable flow rates during the infusion period.
2Ease of operation
If conventional inflatable elastomeric bladders are used, then the device can be filled by hand with a syringe, but an inordinate amount of force is required
Solution Approach 1:
The patent applies preliminary action by pre-designing the bladder's mechanical properties (wall thickness, material hardness, initial volume) to optimize its compliance and expandability. This preliminary configuration ensures that the bladder can be filled manually with reasonable force while still achieving the required pressure and volume for controlled liquid delivery.
3Productivity
If conventional inflatable elastomeric bladders are used, then the device can function as a pressurized reservoir, but liquid remains in the bladder at the end of the infusion period
Solution Approach 1:
The patent applies partial action by designing the bladder to contract only to the extent necessary to dispense the required liquid volume, leaving a small residual amount. The controlled contraction from maximum volume back toward initial volume ensures substantial liquid expulsion while accepting a minimal residual volume, optimizing the balance between complete dispensing and bladder integrity.
4Force
If the bladder walls are made thinner to reduce filling force, then manual filling becomes easier, but pressure stability during infusion deteriorates
Solution Approach 1:
The patent resolves this contradiction by optimizing the wall thickness parameter within a specific ratio range (0.08 to 0.15 times the initial inner radius) and selecting appropriate material hardness (Shore 20A-40A). This parameter optimization ensures the bladder walls are thin enough to allow easy manual filling while maintaining sufficient structural integrity to provide pressure stability during infusion.
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 improved pump achieves a uniform flow rate of at least 60% of the fill volume at pressures of 6.0-14.0 psig, ensuring nearly complete liquid expulsion with less than 4 ml residual volume, addressing the variability issues of prior art devices.
Implementation Method 1
an inflatable tube disposed concentrically about the mandrel... having a wall thickness such that: (0.4225×r)t≤(0.660×r)t. The elastomeric material is desirably an elastomeric silicone... the introduction of a volume of liquid (vliquid) between the mandrel and the inflatable tube expands and pressurizes the tube such that the pump subsequently dispenses substantially all the volume of liquid through the first port upon contraction of the tube
Data Source
AI summary
An improved elastomeric pump for an infusion assembly. The pump includes a generally cylindrical mandrel body with first end, an opposed second end, a length, an outer diameter corresponding to a first radius (Rmandrel), a central bore extending through the length, a first port extending from the outer diameter to the bore to provide a fluid passageway, a fill port and an exit port in fluid communication with the bore. The pump includes an inflatable elastomeric tube disposed concentrically about the mandrel, the tube being sealingly secured on the mandrel near the respective ends of the tube and having an original inner diameter that corresponds to a second radius (r) so that it approximately matches the outer diameter of the mandrel (Rmandrel), a length (L) less than the length of the mandrel, a wall thickness (t) such that:(0.4225×r)<t≤(0.660×r).