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Topic: Magnetic door latch

William Hooper
Phenomenal Film Handler

Posts: 1879
From: Mobile, AL USA
Registered: Jun 99

posted 11-30-2005 12:14 AM

quote: Daryl C. W. O'Shea
In many places it wouldn't be legal to have a door close automatically (via an automation relay) without a bell or light signal

Extend the axle of the door closer mechanism, gear it up, & mount end-of-reel alarms on them.

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Wolff King Morrow
Master Film Handler

Posts: 490
From: Denton, TX, USA
Registered: Feb 2004

posted 11-30-2005 12:27 AM

quote: Daryl C. W. O'Shea
Yeah. We're talking about the exact same thing. Having doors close by themselves is, depending on the jurisdiction, either a building code violation or liability risk. It doesn't matter that it's an electromagnet and pneumatic cylinder and not a motor causing it to close (or stay open).

What about in a grocery store when the doors close after a few seconds?

Regardless, the key difference is these doors are not actually closed forcefully. They are simple released to drift closed on their own. I'd have to think that's perfectly legal, since these doors will naturally drift closed after someone opens them anyway.

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Carl Martin
Phenomenal Film Handler

Posts: 1424
From: Oakland, CA, USA
Registered: Feb 2002

posted 11-30-2005 03:00 AM

perhaps the swinging grocery store doors drift closed of their own accord, but the sliding ones are powered. i once got mooshed by a pair of those when i was little. freaked me out. it didn't kill me, but it scarred me for life.

carl

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David Buckley
Jedi Master Film Handler

Posts: 525
From: Oxford, N. Canterbury, New Zealand
Registered: Aug 2004

posted 11-30-2005 04:55 AM

Just a note to say that these door hold electromagnets exist in two families, those that use power to hold the door open, and those that when power is applied will release the doors.

The choice of which one to use is made on the basis of how you would like them to "fail safe" (ie when the mains fails how do you want the doors to behave); fire doors are normally held open, drop power to close, otherwise its no power is held open, power on to release.

They also exist as wimp varieties, which will hold a door unless someone tugs the door whereupon the magnet is overcome, and the strong variety, usually used for keeping doors closed, which you will break the door before the magnet lets go. These lattter types are usually used in conjunction with card readers and have a "break the glass" release to emergency to open the door.

Any half-decent supplier of access control products will have these products available

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