valve actuation mechanism help

[picclock]

I have a mechanism in which a valve has a sealed shaft running through it. The valve direction of operation is opposite that of the shaft motion. I figure I can do this by using a see-saw type lever acting on a bush incorporated into the shaft. Having looked it over it just seems that its unlikely to work well or easily.

All the circles in the sketch represent oring seals with the exception of the two in the centre of the levers, which represent pivots. The disc has a collar attached underneath which seals to the shaft with an oring.

At the time of opening the main disc valve there is little or no pressure on it, as this has been equalised by the collar further down the shaft venting any pressure difference via the narrower rod section. However the disc needs to be pushed squarely by the pivoted levers and in a fashion that will not cause binding. The disc will close by pressure provided from a light spring not shown in the sketch.

So I guess I'm looking for a better lever arrangement or design which will allow pressure applied to the disk to be equal and square to the direction of movement.

Any thoughts much appreciated.

Best Regards

picclock

 

[Ken I]

Picclock, I not entirely sure I follow your diagram but valvegear is typically 90° out of phase with the cylinder - a "see-saw" is going to be 180° - so I don't see it working.

I could be way off here and will be watching closely.

Ken

 

[picclock]

Hi Ken

No cylinder, piston or rotary motion involved here. Its part of a gas / fluid exchange mechanism. The speed of operation is slow - say once a second. The mechanism is operated by the central rod which does other stuff not shown.

hope this helps

Best Regards

picclock

 

[Groomengineering]

Hi picclock

How about a cam type lever? Shape would depend on the shaft travel and the valve travel and yada, yada, yada.....

Quick drawing included.

Cheers

Jeff

 

[picclock]

@Jeff

Thanks very much for your input. That's pretty much the kind of thing I was going for. But it suffers from the same problem in that the disk is only pushed down at the points where the cam touches, so that it may not be being pushed squarely and jam.

It may just be that I am overthinking it and it would work OK with 2 levers anyway. Just thought that there may be a nifty'er mechanism that would do the trick. Either way I will make a rough one to try it out and see if it can be improved.

Best Regards

picclock

 

[mklotz]

How about a "washer" with two, half-circle inclined planes machined into its face (picture a rotobroach). As the washer is turned the inclined planes bear against two fixed pins and this provides a downward force on the bush that is part of the shaft?

If two pins don't provide a suitably uniform force, use more pins.

 

[Groomengineering]

picclock,

Yea, I was thinking you'd need at least three levers for this kind of setup to work.

Cheers

Jeff