Samsonite Focus Attache gravity latch/lock replacement part

The “gravity lock”, patented “right-side-up feature”, of my 27 year old vintage Samsonite Focus 4″ attache broke. Everything else was still working fine.

Samsonite could only change the whole lock mechanism as the Singapore distributor I contacted didn’t have the replacement part.

When it was fully working, my Samsonite Focus attache could do the following activities:

1. allowed the case to be opened when right side up.
2. allowed case to be opened vertically to access the portfolio compartment at the back.
3. prevents the lock from opening when the case is upside down.

You can see the patent here: https://patents.google.com/patent/US3828899

The plastic latch shown is item 28-32 in the patent. Mine broke.

For the case to perform activity 2, the latch has to be finely balanced;

Item 29 must weigh the same as item 28,31,32 so that it releases the catch when the case was vertical.

In my first attempt, I tried to beef up the high stress areas but then the case could only do activities 1 and 3. After much time consuming trial and error, I finally got the required balance when printing using PLA filament.

Now I understood why Samsonite didn’t further reinforce the high stress area of the hook. Had they done it, the balance would be off and the case won’t be able to open vertically. But now that we are able to print the spare part, we can prolong the lifespan of our Samsonite Focus attache case. It seems like the recent versions of Samsonite Focus attache doesn’t support activity 2 so the vintage versions are much better.

I am including the 3mf files that I used with Microsoft 3D builder with the “shape tools” I used to shape the latch. Just before exporting to STL file format for printing, remove all the “shape tools” and merge all the parts together.