ECN Forum Forums Photo Discussion Forums Electrical Nostalgia Older twistlock and other odd receptacle

The crowfoot plug has been around since at least 1916, as shown in this patent diagrams http://www.videokarma.org/attachment.php?attachmentid=165339&d=1256685729
Another odd outlet: 120VAC 20A

Is there a standard polarity when these sockets are used on 120V?
I'm doing some research for an article on my website with regards to the history of the Australian plug and socket and this is one of my unanswered questions.
As I've explained here previously, this socket design was adopted officially by Australia in 1937, from the U.S, so it is no coincidence Australian plugs fit in the surviving U.S examples.
In Australia the two angled pins could be connected with live and neutral either way round but by the 1960's the convention was live on the left and neutral on the right. This was eventually made compulsory.
However, in Argentina where this socket is also used, the polarity is the other way round.
Or was this socket only intended for 240V use in the U.S?

Unfortunately the videokarma site doesn't allow access for unregistered users.
The "T" configuration outlet is officially used in Australia for extra low voltage applications (<32V) and has become very popular in recent years for 12V use in boats, caravans etc. However, its original use in Australia was for 32V DC farm lighting plants. Only a few days ago I found an article in a 1920's issue of the U.S magazine "Popular Mechanics" showing its use for the same thing. Readers were advised to use it so as to maintain correct polarity for the radio plugged into the outlet. Again, another U.S socket adopted by Australia.

The T configuration was used as the 12V charger connection on older fire trucks for years. A receptacle was mounted on the tailboard or battery compartment. Most newer trucks have an onboard charger/maintainer supplied by a 120V shore cord. Our club buys and restores old fire trucks, and we have a box of these plugs & receptacles. The older trucks, if you started the truck and drove out with the charger connected it would just pull out. Newer trucks have auto-eject inlets that have a n ejection pin that pushes the plug out when you turn the ignition on.

We did the same thing when I was a plant engineer at Beech Aircraft Corp. in Wichita, except that we used crowsfoot receptacles. The old-school management thought it would keep the workers from stealing power tools, but most guys knowledgable enough to use a power tool knew how to replace the plugs! We finally did a mass changer-over to standard NEMA 120V grounded outlets around 1977, which entailed replacing thousands of the old crowfoot outlets throughout numerous factory buildings.

Here's that crowfoot plug as seen in a patent issued in 1916. This patent looks like it invented the 3 pin grounding plug, and this example in the crowfoot pattern. This inventor worked for Hubbell.

This is absolutely astounding! At long last we see the real origin of the Australian plug and I can continue piecing together its history.
It is now clear that it was intended for ordinary domestic 120V use in the U.S, and we simply used it on 240V in Australia as was also done for a while with the non polarised version of NEMA 1-15.
Next question is, was the NEMA 1-15 invented before or after this? If before, I can see why the 3 flat pin plug did not become the U.S standard (much annoyance in not being able to plug in existing appliances with 2 pin plugs). However, had the U.S emphasised earthing of appliances earlier than it did, both countries could well be using the same plug today.
Thank you for this fascinating part of history.

It's hard to really tell from digging around the US patent office, but I see a 2 prong NEMA 1-15 plug mentioned a year earlier than the crowfoot 3 prong Aussie style plug.

Looks like this is the case, that crowfoot outlets post dated the 1-15 and the crowfoot didn't allow the use of 1-15 plugs. I did see later on a 1-15 outlet with a 3rd flat pin, looking like |_| but as we know, it didn't get accepted.

can you identify this 240V with ground receptacle...name, manuf, purpose, etc...

I am still an young one but from what I know that is not a 240 Volt receptacle
It is a tandem/Parallel Outlet the older plugs were a tandem blade design and modern plugs are a polarized parallel design (That outlet not being polarized)

The newer design of that outlet is polarized and both slots look like a 20A T slot receptacle