After determining that operating the LN2 sample dewar without a lid was going to be problematic with regards to ice accumulation in the liquid nitrogen I decided to design and install a pneumatically operated guillotine lid. Here is a nice aerial shot of the closed lid.
hit the jump for details and more pics…
I used low profile linear bearings from Rollon Corp. They are very stiff and can support more lid than I ever plan to put on them. Also they were only 22mm high, a very good feature when designing the lid so the robot tongs would not collide with the bearings.
Here is the lid open. Notice two heaters on the lid to prevent condensation. The foam under the aluminum lid is only 22mm thick and isn’t quite enough to prevent cooling of the Aluminum and condensation.
This slot is for the eventual addition of a laminar flow fan system for drawing off the frosty air that lingers above the liquid nitrogen when the lid is open.
A couple more shots of the leading edge of the “guillotine” in the open and closed positions.