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-   -   Another unusual plug and some other questions (https://www.vintage-radio.net/forum/showthread.php?t=71262)

Phil G4SPZ 19th Jan 2012 11:57 pm

Re: Another unusual plug and some other questions
 
Quote:

Originally Posted by AndiiT (Post 445079)
a switch which would not move to the on position until the plug was inserted and the plug could not be removed once the switch was in the on position.

Interlocked plugs and sockets were widely used in hospitals as a precaution against causing explosions in operating theatres due to the flammable anaesthetic gases in use. Notched earth pins fitted sockets which had a sparkless mercury bottle tilt-switch behind the fascia plate. Wandsworth and Walsall were popular makes.

I also seem to recall 13-amp BS1363 plugs with the earth pin set at 90 degrees to the live and neutral, and I think these were unfused plugs made specially for mobile X-ray machines to restrict their use to special sockets with a very low source impedance.

Interesting thread, this!

Herald1360 20th Jan 2012 1:00 am

Re: Another unusual plug and some other questions
 
That just sounds like Walsall gauge. (All pins at right angles to normal orientation).

If no fuse was an issue (Inrush current?) a 15A round pin plug would seem more appropriate, and still to a recognised standard.

Surely, though, the earth pin on an ordinary 13A plug is set at right angles to the line and neutral pins anyway?

emeritus 20th Jan 2012 1:53 am

Re: Another unusual plug and some other questions
 
In the late 1960s the Electrical Engineering laboratories of University College, Cardiff used Walsall gauge plugs for the public 240VDC mains supply. By 1969 the only other customer of the public DC supply was the municipal trolleybus system, and they were being phased out as the DC power station at Colchester Avenue was nearly life-expired. The labs therefore had to install a motor-generator set for DC machines experiments.

Some of the equipment in the electronics lab was fitted with stacking 13A AC plugs to BS1363, but I don't recall the manufacturer.

Herald1360 20th Jan 2012 5:14 pm

Re: Another unusual plug and some other questions
 
That could cause some interesting confusion if the top plug in the stack (or its load) blew "the" fuse, or did the through connection run up the stack unfused?

Leon Crampin 20th Jan 2012 8:20 pm

Re: Another unusual plug and some other questions
 
The stacking 13A plugs were made by Clix - I still have a few. The fuse protects both the connected load and the socket for the subsequent plug, so if you fit a 3A fuse to protect a light load, the fuse will blow if a heavy load is plugged into the first plug.

They were reasonably well made although the cable grip was a bit crude - a plastic grubscrew.

Leon.

Phil G4SPZ 20th Jan 2012 10:03 pm

Re: Another unusual plug and some other questions
 
Quote:

Originally Posted by Herald1360 (Post 497582)
That just sounds like Walsall gauge. (All pins at right angles to normal orientation). Surely, though, the earth pin on an ordinary 13A plug is set at right angles to the line and neutral pins anyway?

Clearly, my memory has failed me yet again. Note to self: "must check facts before relying solely on memory for a Forum posting."

What I recalled were plugs with the earth pin at right-angles to its normal BS1363 orientation, i.e. horizontal rather than vertical, and I thought the live and neutral pins were normal, i.e. horizontal.

I'll now shut up, and limit my involvement to reading the postings from members whose memories are more reliable than mine - and who know what they're talking about!

emeritus 21st Jan 2012 2:02 am

Re: Another unusual plug and some other questions
 
4 Attachment(s)
Thanks for the info on the "Clix" stacking plugs. We never had the inclination to investigate the insides of the plugs as we were too busy with our experiments.

I have posted some more examples of the use of “Lights” and “Amps” to describe current ratings. The installation costs estimates use “Lights” for the switches and “Amp” for the cut-outs. The installations are for a 50V DC supply voltage using 16CP lamps which, as has been observed, did consume about 1 Amp, so on a 50V system, 1 Light did mean 1 Amp. Perhaps 50V was preferred for private lighting systems before public electricity supplies became widely available.

Re Hubbell's plug, the date of 1904 that is given on the Wikipedia's AC plugs site seems to be based on information that used to appear on the Hubbell web site but has since been removed. The earliest Hubbell patent I have found that illustrates something like the present US flat pin plug configuration is US 1,064,833 that was filed on Jan 2, 1912, but it has detents in the edges of the pins rather than the central holes that are still found on some US plugs.

The drawings of both US 783,275 of 1904 shown on Wikipedia, and US 776,326, filed by Hubbell on the same date, clearly show round pin plugs of the European pattern. Hubbell’s invention lay in the provision of jackplug-like detents in the ends of the prongs to prevent the plug from falling out of the adopter when hanging from a pendant lampholder. US 776326 "Multiple attachment plug" is possibly the first multi-way adapter. Its Fig 4 shows a 3 way socket adopter for the round pin latching plugs, plugged into what is described as "a receptacle of any ordinary type" that seems from the drawings to consist of a square insulating plug having two contact strips on opposite faces: think of a square Schuko plug with no pins where the earth strips are as wide as the sides and are used as the two contacts. Hubbell did patent a flat pin latching plug in 1905, US 793,197, but the pins lay in the same plane like a UK BS1363 plug; a polarised 2 pin plug with two flat pins oriented at right angles [as was/is used in New Zealand?] ; and in his patent US923,179 of 1909, a plug with parallel flat pins similar to the present US pattern, but with the pins shaped like sugar tongs to provide latching detents.

US 1,064,833 can be viewed at the EPO’s Espace web site at the following link:
http://worldwide.espacenet.com/publi...m&locale=en_EP

US 776, 326 here: http://worldwide.espacenet.com/publi...m&locale=en_EP

emeritus 28th Jan 2012 2:27 pm

Re: Another unusual plug and some other questions
 
The “receptacle of any ordinary type” that is shown on Fig 4 of Hubbell’s patent US 776,326 seems much the same as the “Kliegl” connector discussed in posts 24, 43 and 105 of the closed thread “Award for the worst plug design …”
https://www.vintage-radio.net/forum/...ad.php?t=57556

G3gener 31st Jan 2012 2:41 am

Re: Another unusual plug and some other questions
 
Thanks,emeritus for the 1893 GEC catalogues. :)

From the GEC catalog I do see the first plug socket system. Hubbell did not know about it I suppose. He just noted that the janitor at an arcade had to remove the power wires separately from a panel and had to note the proper order before moving the machines in order to clean around them. That's when in 1904 he tried a round pin design,then the tandem blade (still used for US 240V),and finally the parallel blade design.
Grounding pins showed up in the 1920s both with US and UK plugs. I always wondered why the German Schuko plugs were not polarized,then I read somewhere both pins carried 120V to make the 240V,so there was no such thing as a neutral wire.

I can still get a BS546/5A 2 pin adaptor at US hardware stores. They call it a "shaver plug". Must be a few places that still have that kind of socket.

The same catalog does explain why Japan has a 100 V system. They decided to stay with the original 100V lamps and everything else followed.

emeritus 7th Feb 2012 1:33 am

Re: Another unusual plug and some other questions
 
4 Attachment(s)
Some more old GEC mains plugs, sockets and adapters from the 1911 catalogue that may be useful to date vintage items. It includes a different design of coax plug from the 1893 offering, evidently introduced around 1897 to overcome deficiencies in the earlier design according to the patent that describes it : http://worldwide.espacenet.com/publi...C&locale=en_EP

Earthed connectors were only offered for industrial and naval use. I used to have two almost identical 5A BS546-type surface mounted sockets, one of which [presumably the older] had its earth terminal sticking out of the top of the socket, no doubt in accordance with the early Home Office Earthing regulations. I remember that my aunt’s house had “Wandsworth” gauge plugs of the Home Office pattern.

Does anyone know anything about the BC adapter plug shown in the photo? It looks as if it is intended to provide an earth connection as the bayonet pin adjacent the groove in the body bears the remains of a screw thread. There is also the remains of another pin closer to the groove that has been cropped. The adaptor carries a patent number 385785 [ granted to GEC] which sets an earliest manufacture date as it was published in 1933, but the patent only relates to the cord grip and its drawings show a BC lampholder. In the second photo a piece of white nylon cord has been threaded through the groove to show how the earth lead might have been brought out.

glowinganode 7th Feb 2012 1:56 pm

Re: Another unusual plug and some other questions
 
I think the bit of string was to attach it to the mains lead to prevent it getting lost when not in use.
Rob.

kalee20 7th Feb 2012 1:56 pm

Re: Another unusual plug and some other questions
 
I've never seen a BC plug with the ability to include an earth connection. Perhaps there was a lead emerging from the side, with a croc clip for clipping to an earthed metal object?

But this sounds highly implausible - if the earthed metal object was only tenuously earthed, then a fault in the appliance could make this object live. Also, the distance from the lamp fitting to such an object would be indeterminate anyway, hardly practical for a portable plug-in appliance.

If the appliance needed an earth, I'm sure a much more practical approach would have been a separate earth connection lead from the appliance itself.

emeritus 7th Feb 2012 3:39 pm

Re: Another unusual plug and some other questions
 
The string is not original. I didn't have any light-coloured wire handy and only used the string to show up the groove in the photo against the black bakelite of the plug.

I suppose it could have been used to attach it to a BC to 2 pin adaptor: 2 pin 5A plugs with captive 2 pin to BC adaptors were extensively used at a schoolfriend's house that in 1970 still had its original 2 pin 5A sockets in every room. I have a example myself, but the cord used is of far smaller size than the dimensions of the groove in my plug, and why is the end of the pin threaded? Earthed pendant lampholders are seldom found today other than in chandeliers, and I don't believe that it was normal practice to provide an earth at ceiling roses in pre-war installations. Older brass lampolders usually have no means of earthing the brass casing other than via the 1/2" tube that they are screwed on to, even if an earth were available.

Both the threaded pin and the other non-bayonet pin show evidence of having been cropped, no doubt so the plug would mate with a conventional shrouded lampholder. The shiny surface of the groove indicates that it was moulded and not ground out subsequently. There is no electrical connection between the threaded and the non-bayonet pin, and only the conventional pair of terminals in the interior of the plug.

rogerla 7th Feb 2012 3:46 pm

Re: Another unusual plug and some other questions
 
In large houses during the 20's/30's, a separate lighting circuit was run to 2 amp sockets adjacent to various positions where people were likely to sit in a room, to allow standard lamps/table lamps to be switched on and off as one entered or left that room, to avoid having to have 'n' large current gobbling ceiling fittings to provide overall high levels of illumination.

There is a 'worldwide plugs and sockets' 'museum' website at http://www.fam-oud.nl/~plugsocket/Overview.html and if you click on the UK map link you will see examples of previous arrangements by (for instance) Wylex and other manufacturers. Not all previous types have yet been captured, so the 'museum' would probably be interested from anyone having pic's of those old devices not yet shown.

I think that the 'staggered flat pin/central round pin' Wylex sockets were used in some organisations to identify circuits connected to secure (generator backed up) circuits etc.

Lucien Nunes 7th Feb 2012 7:56 pm

Re: Another unusual plug and some other questions
 
That BC adaptor is fascinating, if the function of the groove and threaded pin are as you suggest. Update - see catalogue pics below!

Yes - I'm sure Oof Oud at the online museum linked-to above would appreciate any interesting UK stuff you can dig out, he does collect the actual fittings not just pictures. I'm slowly gathering a selection of BS546 bits to send over. I sent some Wylex items and Oof very kindly organised sending a parcel of Dutch wiring materials for display at Electrokinetica!

Lucien

Lucien Nunes 7th Feb 2012 8:09 pm

Re: Another unusual plug and some other questions
 
2 Attachment(s)
Never noticed it before but it's in the 1936 catalogue as an earthed adaptor - see pics.

Lucien

Herald1360 7th Feb 2012 8:18 pm

Re: Another unusual plug and some other questions
 
So it would pick up its earth from a metal shelled bulb holder, presumably.

It would work all right with modern brass lampholders which do have an earth connection.

Still looks a bit hairy, though.

Are there any such in the old catalogue to match the adaptor?

kalee20 7th Feb 2012 8:44 pm

Re: Another unusual plug and some other questions
 
Quote:

Originally Posted by emeritus (Post 502258)
Earthed pendant lampholders are seldom found today other than in chandeliers, and I don't believe that it was normal practice to provide an earth at ceiling roses in pre-war installations.

That's what I thought - it's extremely unlikely that an earth connection would be available at the lampholder itself. (If there was, then using a bit of cunning, a connection could have been fashioned using the transverse bayonet locking pins, which are in intimite contact with the lampholder's locking cut-outs, effectively making a 3-way connector out of the system).

Edit - I had this post open for a fair time, during which others have pointed out that earthed bayonet connectors really did exist!

Lucien Nunes 7th Feb 2012 9:06 pm

Re: Another unusual plug and some other questions
 
The catalogue lists cord-grip pendant lampholders S1143 and S1143A 'With visible earth terminal' and an option to have the wooden cable grip collets in extra-large size with a single hole in place of the customary two for twisted twin. There are also switched versions S1473 and S1323. No pictures unfortunately.

Earth terminals aren't mentioned for threaded entry lampholders presumably because they expected continuity from the wiring system.

Lucien

emeritus 8th Feb 2012 1:18 am

Re: Another unusual plug and some other questions
 
Thank you very much Lucien for identifying the adapter. I had searched for GEC patents in the range 1930 to 1940, but I see that the patent GB 294317 that is mentioned in the 1936 catalogue was issued in 1928: copy available here:

http://worldwide.espacenet.com/publi...m&locale=en_EP

From the picture in the 1936 catalogue and Figures 1 and 2 of the patent, it seems that I have a Friday afternoon model where the normal bayonet pin and the threaded pin have been transposed: no wonder I was having problems in working out how it would work with a bayonet pin being used as a terminal! The catalogue also explains why the cover was so much longer than the other BC adaptors in my collection.

The use of the metal case of the lampholder as an electrode was evidently still practiced in 1936 in the form of the CC (centre contact) lampholder listed as S719 that is just visisble at the bottom of 1936 GEC catalogue extract, presumably for low voltage use.


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