Locking Mechanism for Overspeed Trip | 30N Weight

[xandro101]

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.

 

[edgepflow]

A simple off-the-shelf air cylinder may work for this.

 

[xandro101]

My design specs is such that i can't use an air cylinder. The trip assembly is to be retrofitted. I am in need of an idea around a push button locking mechanism. Thanks. Pls let me know if u have another idea. Thanks again.

 

[edgepflow]

There are a couple of other possibilities I can think of:

a) linear solenoid actuator
b) electric actuator for a quarter turn valve.

 

[xandro101]

Edgepflow, thanks again. But my specs state that the overspeed trip should not be powered by batteries or an external power source as it must not fail when needed to function. So it must get its power from the main shaft of the prime mover for which it is being designed. This is to ensure that the trip does not fail to work should there be problems with power supply or the batteries. It is like a pure mechanical system. I have actually come up with a concept which I think will do the job mechanically. It is just that I need a locking mechanism for a dead weight to keep it at height and release it to turn a lever (to which the weight is welded) about a fulcrum thereby providing a torque at the other end to drive a rack and pinion mechanism that will turn a stop valve shut. But the dead weight must be released only when a pawl from a centrifugal sensing mechanism rotating with the shaft actuates the lock mechanism to do so. Then when the plant needs to be used again the trip has to be reset and the weight raised to its original position and stay locked until when released. This resetting has been arranged for but I'm in need of a lock that can perform both locking the weight when it is coming up during resetting and hold the weight up there until it is needed to do work. I will appreciate further suggestions if u now get what I'm saying. Thanks in advance.

 

[edgepflow]

That is a strange spec but I have seen stranger. It really limits your choices.

Try a mechanical ratchet and pawl.

 

[DickL]

I've done a lot of work with fail safe system designs, and generally I trust properly implemented electrical and electronic fail safe system implementations more than all be the simplest of mechanical designs (and I'm a mechanical engineer). If this fail safe protection includes personnel safety, then you may want to look at non-mechanical approaches. A spring closed gate valve, that is held open with an energized solenoid would seem to me a safer and more reliable approach. Removing power from the solenoid is easily implemented by the over speed trip.

 

[xandro101]

Thanks DickL. I understand what you mean but this one requires a pure mechanical system. That is what the specs state. It is a design project that I am trying to work on to gain more experience and hone my skills as a newly graduated mech. Engr. So it will be best if I fufill the requirements and show that the design is possible.