Film-Tech Forum ARCHIVE: Magnetic door latch

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Posted by Brad Miller (Member # 2) on 11-04-2005, 12:52 AM:

Some theaters out there are using these, can someone post some info on what they are using? Essentially it is a magnetic latch that when energized will hold the auditorium door open, and then when the feature begins, a latching relay closure from the automation opens to cut power to the magnet and the door closes. Then at the end of the show the automation latches that relay to provide power to the magnet and the first person to open the door all the way will permit the magnet to hold it open.

It's very simple and a nice way to guarantee that the auditorium doors are always closed at the beginning of the feature. Anyone have some specific models or info to pass on? [Smile]

Posted by Phil Hill (Member # 371) on 11-04-2005, 01:13 AM:

[ 11-04-2005, 07:16 PM: Message edited by: Phil Hill ]

Posted by Monte L Fullmer (Member # 2797) on 11-04-2005, 01:46 AM:

Yep, the same magnetic door latch assemblies that we have in some of our theatres (that were built by Cineplex Odeon until they had to pull out of a wad of towns..).

This is one area that I need to find out if I do have automation access (through my CPA-10's) to these doors to close on feature start.

Right now, there is a push button right below the e-magnet that interrupts the field to allow door closure.

-Monte

Posted by Jack Ondracek (Member # 1466) on 11-04-2005, 02:07 AM:

We have a Regal 12-plex here that uses latches like what Phil posted the link to. They're set up like Brad describes... Doors shut somewhere in the presentation. It appears that power-on is tied to the cue they use to bring the lites up at credits.

Posted by Mark Hajducki (Member # 1732) on 11-04-2005, 06:45 AM:

There are two different systems like this, one is built into the door closer unit (at the top of the door), the other is a seperate magnetic hook (usually) lower down the door.

The hook type are usually less strong so that if somebody pulls the door it will close when the built into the closer type may cause damage to the door if somebody 'helpfully' decides to close the door early.

Remember to make the doors close slowly so as to avoid damage to loitering customers

Posted by Leo Enticknap (Member # 534) on 11-04-2005, 02:53 PM:

Interesting. At the last cinema I worked, we had magnetic hook catches on the internal fire doors, which were linked to the alarm system. It never occured to me that having them on the screen doors and operated from the booth (either manually or on the 'feature start' automation cue) would get round the problem of usherettes constantly leaving doors wedged open, and one or two occasions when customers tripped over the wedges.

Posted by Dan Harris (Member # 1759) on 11-04-2005, 05:48 PM:

We have these as standard on new builds, in the form of a latch at the top outer corner of each door. They are tied into the automation and the fire alarm. It ensures the doors are open during ads/trailers, close automatically when the feature starts and latch open on the end credits.

A single push-to-break switch mounted between the inner and outer sets of auditorium doors interrupts the power supply. They require a power supply, which is usually mounted in the booth, and have a local backup battery in case of mains failure.

Picture shows a theatre during fit out with the doors and magnetic latches just mounted.

Posted by Brad Miller (Member # 2) on 11-04-2005, 06:02 PM:

Dan, that is exactly what I am looking for. Can you get me a brand and model number of those units please?

Posted by Dan Harris (Member # 1759) on 11-04-2005, 06:09 PM:

I'll have a look when I'm next at work (tomorrow night). If I can't find any documentation on site I'll get onto someone 'in the know' after the weekend.

UPDATE: I couldn't find any documentation, however I am waiting for an email/call back from someone.

[ 11-07-2005, 06:54 AM: Message edited by: Dan Harris ]

Posted by Brad Miller (Member # 2) on 11-29-2005, 12:27 AM:

Anyone else have a specific model that they find relatively inexpensive, simple and reliable?

Posted by Bernard Tonks (Member # 809) on 11-29-2005, 05:13 AM:

I had a chat with someone who used to fit out hotels. He said that you should look for magnetic door releases.

http://www.protectingpeople.co.uk/fire/door_retainers_releases/

This looks like what Dan has been trying to find out for you. And available 24 volt DC with automated options.

Posted by Tristan Lane (Member # 1169) on 11-29-2005, 06:29 PM:

Grainger has them: Link

Posted by Daryl C. W. O'Shea (Member # 1303) on 11-29-2005, 10:29 PM:

I've always used what ever the lock company stocked. I've never been picky about brand/model... after all they're just an electromagnet.

I'm still against them being used for anything but fire code compliance in public spaces though. In many places it wouldn't be legal to have a door close automatically (via an automation relay) without a bell or light signal. At a minimum I'd have the yellow caution stickers you see on doors operated via an automatic door opener stuck to the door.

Somebody's liable to walk into a closing door and sue you for them breaking their nose. Use a button, and get someone to push it sometime near the end of your pre-feature line up.

Posted by Brad Miller (Member # 2) on 11-29-2005, 10:47 PM:

The door closure is to remain on the door. It's not like this is a motorized door closure. It simply will release the door so that it may slowly close.

Posted by Daryl C. W. O'Shea (Member # 1303) on 11-29-2005, 10:49 PM:

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).

Posted by William Hooper (Member # 71) on 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.

Posted by Wolff King Morrow (Member # 2226) on 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.

Posted by Carl Martin (Member # 1146) on 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

Posted by David Buckley (Member # 2600) on 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