User Need
Many developing nations lack the medical facilities and resources that are able to create a specified low pressure zone, and a low pressure zone from a pump is critical for the use of The InPress Postpartum Hemorrhage Intrauterine Device. As such, Cal Poly's Appropriate Technology team has been tasked with designing and prototyping a pump that can be used for InPress' Device. The goal is to create an affordable, robust, and universal design that can succeed in a variety of conditions and environments.
Current Design
DESIGN SUMMARY
The current design is intended to hold a pressure without needing continual pumping from the user. It achieves this by using simple pressure lines and check valves to keep the pressure within medical range. The design is made up of almost entirely commercially available products, and it uses a plunger with a coil diaphragm to help regulate the pressure.
DESIGN CHANGES
- Eliminates the complexity of the previous design by using commercially available check valves to regulate the flow and pressure differential.
- Possess a new coil spring diaphragm to buffer the pressure. This makes the pump safer by decreasing the chance of sudden pressure changes or spikes.
The current design is intended to hold a pressure without needing continual pumping from the user. It achieves this by using simple pressure lines and check valves to keep the pressure within medical range. The design is made up of almost entirely commercially available products, and it uses a plunger with a coil diaphragm to help regulate the pressure.
DESIGN CHANGES
- Eliminates the complexity of the previous design by using commercially available check valves to regulate the flow and pressure differential.
- Possess a new coil spring diaphragm to buffer the pressure. This makes the pump safer by decreasing the chance of sudden pressure changes or spikes.
Previous Design
DESIGN SUMMARY
The first prototype is a small induction pump using two reed valves to create low pressure in both the pump draw and the pump push. In a postpartum hemorrhage case, a midwife, nurse, or doctor, can apply continual pumping to create the low pressure zone needed to contract the uterus. The model can be fitted to any commonly available 50mL syringe. This makes it easy for doctors and clinics to use their own equipment. It also makes the produce more cost effective. There is no need to purchase numerous specialty parts, because the only custom piece is the pump casing. The design was prototyped with a 3D printed model and tested to see how well the reed valves worked, and how well it could hold pressure.
The first prototype is a small induction pump using two reed valves to create low pressure in both the pump draw and the pump push. In a postpartum hemorrhage case, a midwife, nurse, or doctor, can apply continual pumping to create the low pressure zone needed to contract the uterus. The model can be fitted to any commonly available 50mL syringe. This makes it easy for doctors and clinics to use their own equipment. It also makes the produce more cost effective. There is no need to purchase numerous specialty parts, because the only custom piece is the pump casing. The design was prototyped with a 3D printed model and tested to see how well the reed valves worked, and how well it could hold pressure.
TESTING
The prototype failed in two main areas when it was tested to see how well it could maintain pressure and pump. First, the reed valves were too stiff to open. When the syringe plunger was pushed down, the resulting jet flow was supposed to open the lower reed. Instead, air leaked around the reed, and it showed no deflection. This leaking air was the second problem. Not only did the jet flow not produce enough pressure to open the reeds, the reeds weren't able to create an air tight seal. Air leaked around the edges, causing the device to fail.
FUTURE PLANS
The air leak and the reed strength both need to be addressed for this design to function. A structural analysis can be performed to properly size the reeds to assure they open at the specified pressure differentials, but that still won't assure their air tight seal. Overall, the reeds are most important part of the pump, and they present themselves as high risk items if they were to fail. It makes more sense to mitigate risk by transitioning to a new design that uses commercially available products to regulate and check flow direction and pressure. This change would allow the design to be more robust, and it may even decrease unit cost, because the highest item part requires no specialty design.
The prototype failed in two main areas when it was tested to see how well it could maintain pressure and pump. First, the reed valves were too stiff to open. When the syringe plunger was pushed down, the resulting jet flow was supposed to open the lower reed. Instead, air leaked around the reed, and it showed no deflection. This leaking air was the second problem. Not only did the jet flow not produce enough pressure to open the reeds, the reeds weren't able to create an air tight seal. Air leaked around the edges, causing the device to fail.
FUTURE PLANS
The air leak and the reed strength both need to be addressed for this design to function. A structural analysis can be performed to properly size the reeds to assure they open at the specified pressure differentials, but that still won't assure their air tight seal. Overall, the reeds are most important part of the pump, and they present themselves as high risk items if they were to fail. It makes more sense to mitigate risk by transitioning to a new design that uses commercially available products to regulate and check flow direction and pressure. This change would allow the design to be more robust, and it may even decrease unit cost, because the highest item part requires no specialty design.