When last we spoke, I was threatening to disclose the function of the slots on the top of J. V. Hammond explosive boxes.

Slots! WHy?

Slots! Why?

The answer can be found in US Patent #2278850 dated April 7th, 1942. The patent was filed February 20th, 1940. It took two years to approve the patent for a wooden box…

I found this patent number on the side of the large box:

There's a patent number there.

There’s a patent number there.

This patent number was not on the previously posted picture of the box because I removed it to stretch the blog out for another week and to look smarter than I really am. The patent explains it thusly:

Formed in the top wall, substantially medially of its width and extending the major portion of its depth, is a dove-tail shaped guide slot.The guide slot communicates with the forward edge of the wall and slidably receives a guide.element which is formed on the under side of a latch member, said latch member being of substantially rectangular shape in cross section and being of a length substantially the same as the depth of the complete dynamite box. As will be seen by referring to Figure 2, the guide element terminates short of the forward end of the latch member a distance equal to the thickness of the front closure presently to be described in more detail.

In order normally to urge the latch member forwardly, I provide a rubber band.

The patent drawings look something like this:

This makes it clear.

This makes it clear.

In reality, it looks like this:

A rubber band what slides the latch closed.

A rubber band what slides the latch closed.

And this:

Showing the latch action.

Showing the latch action. I had to build the latch.

When the lid is opened, the latch slides back out-of-the-way:

The lid holds the latch out of the way.

The lid holds the latch back.

Close the lid, and the latch is automatically returns to the locked position:

Powered by a single rubber band.

Powered by a single rubber band.

The patent reveals that the box was designed to not fall apart (dovetails), be made without any metal parts (pegs) and to latch automatically (rubber band), all good things when your intent is to carry explosives into a dangerous environment. You can read the patent HERE.

Hammond built their box in several sizes sharing the same basic construction:

Still looking for more sizes to fill out the collection.

Image borrowed from an online auction site. Used without permission because this is the internet.

Reader Jeff Kester described the latch in a comment earlier in the week. I just found and approved his comment five minutes ago. I’m not sure how that happened…

I am looking for a catalog or manual so I can order some appropriate replacement parts. Let me know if you have one.