Storage for 1/2" open reel tape

[Paul Koning]

> On Apr 5, 2019, at 7:15 PM, Grant Taylor via cctalk <cctalk at classiccmp.org> wrote:
> 
>> ...
>> But basically, just behind the "hook", there's a black plastic latch. When closed, it tensions the white band.
>> https://www.electronicsurplus.it/open2b/var/products/27/92/0-d95b2a25-800.jpg
> 
> ACK
> 
> I'm getting the mental impression that it's somewhat like a spring form pan.  The latch opens and releases tension off of the strip that goes around the tape reel.  When it's latched, it cinches against it.  When it's unlatched, there's enough play to allow the tape reel to come out.
> 
> Am I remotely close?

Correct.  The latch has a thin section which acts as a flexible hinge, and the other end hooks around a hook shape molded into the tip of the white band.  When you push the latch against the reel it snaps closed and spring tension holds it that way.

The autoloading latch (in http://www.columbia.edu/cu/computinghistory/media.html) is somewhat similar but with some important differences.  The latch can flex around the thin part near the left end.  There are actually two parts, pinned together so the thing essentially folds over itself.  And the far end in turn is pinned to the tape seal (the end to the right of the seam, in the photo).  You mount it into the drive seal and all.  The drive has a mechanism that engages the latch and flips it open, which unfolds the folded latch shape and thereby forces the two ends of the seal apart maybe 3/4 inch.  There are some locating shapes that keep the two ends aligned, you can see the button that does this just to the right of the latch, its stud moves in a slot on the seal band.   That sliding action opens up a window (holes in the two halves slide to align).  So at this point the reel can rotate freely because the seal is no longer clamped onto the rim, and air blowing through holes in the seal blows the end of the tape out through that window.  To make this more reliable the end of the tape is cut with a arced end and sometimes stiffened slightly.  The vacuum system picks up that end, pulls it through the tape path, sucks it onto the takeup hub, and presto changeo, the tape is loaded.

Usually.

If this works, which is most of the time, it's a great time saver.  As an operator you just hang the reel on the spindle, hit "load" and walk away to the next task.

I think IBM may have originated this magic; several of the later DEC tape drives supported it as well (TU77 and TU/TA78, if memory serves).

	paul