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xandro101
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Join Date: May 2011
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Locking Mechanism

05/25/2011 2:01 PM

I am working on a concept for an overspeed trip mechanism. I'm almost done with this except for this one thing: i need a locking mechanism that will hold a dead weight at a height so that this weight is only released only when the lock is actuated to realease it. But that's not all. When resetting the overspeed trip the weight is to be raised back to its original position to be locked again in this position. This resetting is done thru an arrangement of gears and a pulley. The weight is about 30N. I will very much appreciate helpful suggestions. I need a lock which will allow the 2 functions described above.
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Doorman
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#1

Re: Locking Mechanism

05/25/2011 2:30 PM

How complicated and wonderful of a solution are you looking for?

A simple solution may be to fix a helical extension spring BELOW the weight. In the normal 'at rest' state, let the weight bear on the spring. Simply deflect the spring a little bit, it will collapse and the weight will fall. The spring will reset itself when the weight is lifted to the point of origin.

Simple, n'est pas?

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xandro101
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#3
In reply to #1

Re: Locking Mechanism

05/26/2011 3:25 AM

Thanks doorman. That is a fine solution. Let me consider how i will engineer the actuating of the lock. Thanks again.
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Tornado
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#2

Re: Locking Mechanism

05/25/2011 11:49 PM

With a bit of tinkering, a regular doorknob could do what you want.

--Doorknobman

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xandro101
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#4
In reply to #2

Re: Locking Mechanism

05/26/2011 3:35 AM

Thanks Tornado. I just thought about it and the doorknob mechanism appears to be a wonerful solution. Thanks again, for broaching it. Alex.
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Doorman
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#6
In reply to #2

Re: Locking Mechanism

05/26/2011 8:28 AM
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Nigh
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#5

Re: Locking Mechanism

05/26/2011 7:01 AM

Perhaps an over centre lock mechanism? This would hold the weight firmly & only need a small sideways force to actuate it.

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xandro101
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#8
In reply to #5

Re: Locking Mechanism

05/26/2011 2:03 PM

Thanks Nigh. Could you pls describe what you mean by an over centre lock is like.
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Doorman
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#9
In reply to #8

Re: Locking Mechanism

05/26/2011 5:34 PM

A locking leg brace for a folding table (card table) is a type of overcenter mechanism.

It would be similar to the spring idea.

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Nigh
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#10
In reply to #9

Re: Locking Mechanism

05/26/2011 6:11 PM

Right, also toggle latches, draw latches etc. I'll knock up a quick sketch when I get to work in the morning.

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xandro101
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#11
In reply to #10

Re: Locking Mechanism

05/27/2011 1:30 AM

Thanks all. @Nigh, i will appreciate the sketch.
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Nigh
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#12
In reply to #11

Re: Locking Mechanism

05/27/2011 5:05 AM

I hope this is clear, over-centre locks can take many forms but the essence is to have a 2 bar linkage in which the centre point has it's travel limited in one direction so that it can just pass the centreline between the end pivots. In the locked position the more weight you apply, the stronger the locking force is. To open you move the centre point to the other side of the centreline & the weight forces the lock open.

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nairck
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#7

Re: Locking Mechanism

05/26/2011 12:02 PM

The operating condition is not clear.It depends upon what operation is focused.Over speed of what is to be tripped. Preferably centrifugal governor design with limit switch is good with limit switch or latch and pin mechanism.

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xandro101
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#13
In reply to #7

Re: Locking Mechanism

05/28/2011 4:46 PM

Thanks for your assistance. I have gotten a solution now. Thanks again.
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