🚀 go-pugleaf

wingo@apple.com (Tony Wingo) writes:
>In article <1992Nov18.033022.4518@bbxrbk>, russ@bbxrbk (Russ
Kepler) wrote:
>> Ahh, but the *real* question is why the prongs have holes in the
tips...
>Back when these plugs were first standardized, manufacturers did
>not have access to corrosion-free spring alloys to make the socket
>contacts out of, so the sockets had spring-loaded detents that
>engaged the holes in the plug contacts, to guarentee a good
>contact.  The holes became part of the specification for the plug,
>so they are still there even though they haven't been necessary
>for a long, long time.

But at least one manufacturer makes use of them.  I have a
humidifier/vaporizer made by DeVilbis (sp?).  It makes the hot
vapor by using two electrodes in the water.  The electrodes and the
enclosure around the electrodes tend to get coated with deposits
(calcium, I believe), and require an occasional cleaning.  To open
the enclosure, you must insert the plug into a place on the
enclosure, which then unlocks.  Then you twist off the top.  I'm
sure they don't want people opening it up, exposing the electrodes,
and then thinking, "Duh, I wonder what would happen if I plug this
into the wall while I have this open.  Duh, let's see what happens
now, while I touch these two metal things."  So what they did is
engineer it so that when you twist off the top of the enclosure,
a pin drops through the holes in the prongs, preventing you from
unplugging the plug from the enclosure.  The pin retracts when you
twist the top back onto the rest of the electrode enclosure,
allowing you to remove the plug again.-- 
                 
         ________________________________
         |                              |
         |          WARNING             |
         |                              |
         |   .sig UNDER CONSTRUCTION    |
         |                              |
         |         PLEASE USE           |
         |       ALTERNATE ROUTE        |
         |                              |
         | (ccuppern@s.psych.uiuc.edu)  |
         |______________________________|