By now everyone knows that my Mom is my greatest inspiration. As she continues to degenerate with Parkinson's Disease I continue to try to come up with technology to make her daily activities easier. For some time now she has been fighting with the tube of Analgesic Pain Cream that she uses to ease the pain in her muscles and joints. In the good old days the tubes of cream came in a metal tube. As one squeezed and collapsed the tube it stayed that way. The tube could be slowly rolled up from the end and all the contents could be extracted. Now days the metal tubes are gone, replaced with springy plastic ones. While I am sure these plastic tubes are much cheaper and probably better for the environment they are a real challenge to use even for a fully coordinated adult. Each time the tube is used and released it expands and aspirates a bunch of air. Each time thereafter the tube must be squeezed until the air is out, before more cream can be obtained. When the cream is getting low one can try to roll the tube from the end towards the cap but it is like a spring and the tube is often slippery with cream from previous fights with the tube.
While researching pumps for my previous device I explored a small gear pump.
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It occurred to me that this gear pump would be perfect for pumping cream from a modern plastic tube. The pump was sold as a 12 Volt pump but experiments have shown that this is way too much power. Optimal voltage for pumping the cream turned out to be between 1 and 2 volts drawing 3 amps. My initial idea was to use AA batteries to supply the power but at the draw of 3 amps this would not be practical. I had some high capacity NiMH 7.2 volt packs that had been used in a Neato Robotic vacuum cleaner. I also had a nifty little 10 Amp variable DC to DC converter that I bought on one of my binges on a Chinese electronics site a while ago. The batteries had been capable of running the Vacuum for about an hour before they had to be charged. Even at 3 Amps for each squirt of cream they should last several tubes of pain cream before they need to be recharged.
Here is the battery pack that will be used:
Here is a picture of the device under construction:
The inlet of the pump is a metal needle sticking out of the white plastic and the outlet will be through the red polyurethane hose. The red tubing will exit the box though an oblong hole in the case and rest on top of a small SPST micro switch. The idea is that a slight downward push on the tubing will activate the switch and turn on the motor. Below is a better picture of the tubing exiting the box.
Since this device is more electrical than electronic I have not produce a schematic for it. The design was more or less dictated by the resources that I had available to build it. I decided to construct a protective cage around the pain cream tube which sticks up from the top of the unit. This will prevent too much stress being placed on the adapter cap which is mounted to the top of the box. Here are pictures of the cage without and with the pain cream tube installed.
The last step was to produce a short video showing how the dispenser works. While there are countless dispensers of soap and other products on the market this is the only one I know that dispenses Walgreen's Analgesic Cream.
John
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