門把手

Update - more optio, more paramete, customizable, stronger joint.
Doorknob Handle
Unfortunately this was ipired by Coronavirus COVID-19
If you think these may help you, your family, or othe, please feel free to customize and print as many as needed.
If you would like to manufacture and commercialize this product please contact me, we can work something out.
Novel Coronavirus or COVID-19 is spread like cold and flu viruses via contact with droplets (sneezes, coughs) from an infected individual. It has been proven viable in the air for 3 hou and has been demotrated to contaminate surfaces for up to 3 days where it may be picked up on hands. A potential vector for infection is touching your face (mouth, nose, or eyes) with the virus on your hands. Frequent thorough hand washing with soap and water and minimizing touching your face are suggested ways to reduce the likelihood of contracting the Novel Coronavirus COVID-19 infection.
Cente for Disease Control:
The use of round doorknobs require a hand to grasp and twist to open a door. Entry and exit doo in particular must be touched by everyone entering a household, are usually touched before having access to a sink, and after potentially touching public handles, railings, shopping carts, elevator butto, ATM's, money, gas pumps, rest rooms... Doo with handles can be opened with elbows and forearms which are less likely to relay infection.
This handle is easy to print and clamps firmly, gently, and non-destructively to round doorknobs.
An added bonus: Handles are easier to open while carrying packages, groceries, or beverages!
Styles
There are two styles, flat (push) and curved (pull).
The flat veion will likely print more easily and is perfectly fine for doo that push open.
The curved veion is tailored for doo that need to be pulled and in general is more univeal.
I can open our doo iide and out with my elbows, but even if you can't get your elbow in there, at least you can limit exposure to one finger rather your whole hand grabbing a doorknob.
You can customize the length, style, size of the doorknob and more in the OpeCAD paramete in the file (even more if you dig into the code - have fun!).
Fitting
The default size is 54mm diameter, 23mm thick doorknob. The model can accommodate slightly larger and smaller sizes as is.
To fit your doorknob you may either scale the STL file before printing (measure your doorknob diameter D and scale by D/54), or adjust the paramete in OpeCAD, render (F6), save STL, and print your customized model.
Itallation
The door handle may be italled horizontally but I like ou elevated (rotated "up") 30-50 degrees to provide more of a usable rotation arc with my elbow.
Attach to doorknob

Slip handle over your doorknob, it should fit snug but not crack
Fasten with a machine screw or bolt (M3, 4-40, 2-56, or anything that will fit)

Lock nuts are preferred to regular nuts
Use of washe on both sides is recommended to distribute forces

If snug enough, it may work fine without a screw
Optional: If your handle slips, you can slip or wrap a rubber band between the doorknob and the ring before tightening the screw. You do not need to put the rubber band around the doorknob (that would be very difficult), it just needs to compress the rubber agait the doorknob in one location to improve grip. Alternately, (more easily) you could wrap a rubber band around one arm of the handle ring prior to itallation as pictured, but the rubber band will be visible once italled.

Note, there should be enough friction to open the door with your elbow or knee
but the plastic handle may not be able to grab the smooth metal doorknob with enough force to secure it agait any force without slipping. Simply slide it back to the original position or you can try italling a rubber band for more "gription".
Conclusion
I will never know, but I hope this is helpful. I hope this has a chance of preventing at least one peon from getting sick - even if it is not agait Coronavirus, perhaps agait one of the 200 viruses known to cause the common cold, or influenza (8,200 deaths in US in 2019), or Norovirus...
Maybe you just want to make it easier to bring in your groceries.
If you would like to support invention for the greater good, you can donate to your local makepace... or mine:

(they will need support during these times of social distancing and isolation)
Also, please don't judge my filthy garage/workshop doo too hahly... I have to go scrub them now.
Stay well, wash your hands, and don't touch your face!