How to translate from vertical motion to rotational

Imagine, if you will...
A valve which is typically actuated via vertical displacement (downward stroke)...

However, I have managed a means to activate the valve via rotational motion.

I was hoping to get a few ideas from the forum on how to translate the vertical motion (I have to deal with this as a prerequisite to design is retrofit to existing product)to rotational.

I need only rotate a 3/8 diameter shaft 50 - 60 degrees...

Any thoughts?

RamPower made RamTough

Rack and pinion.
Linkage connecting a lever arm on your rotational element to the linear element.

I agree with Mandrake22, from the sounds of it you're just describing a fairly typical rack & pinion linear actuator for quarter-turn ball valves.  We use them all the time for emergency shutdown valves.  Readily available for pretty much anyone who makes rotary control valves - Fisher, Bettis, Flowserve, come to mind.  Here's a link to one of flowserve's designs (this one's pneumatic piston operated with a spring return).

http://www.flowserve.com/valves/automation/pages/heavy_duty.stm

We have designed and built several of our own scotch-yoke actuators for specialty sub-sea applications.  They really are not complicated (in their simplest form anyways) yet are very reliable and rugged.  Sounds to me like what you need would be available from any of a number of vendors.  We have used Bettis in the past for standard applications and had good results.

Denande

Yeah, I see what you're up to.

I would use a trick utilized with downhole equipment such as packer or wireline apparatus in the oilfield.  Cut a closed J Slot into the stem of the valve, and have a pair of lugs "cam" rotational motion as the stem rises or falls.

Alternatively, you should be able to simplify rotational motion by cutting a helix into the stem and have rotational motion as a consequence to a pair of lugs riding in the slot.  This would be more cost effective and easily machinable with a mill.  In addition, you get a compact design without the need of a bulky Scotch Yoke mechanism to translate linear to rotational motion.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

It's a problem Watt struggled with, but which Peaucellier solved..  Do a google search for "Peaucellier Cell"

The best approach may be influenced by other dimensional and actuator force constraints.  

I have an application where I use essentially Cockroach's alternative (helix) to obtain 60 degree rotation from linear input.  The rotation output axis is coincident with the line of action of the linear input.  

The pitch of the helix for a given 60 degree rotation determines the linear stroke.  The peak force required for the linear input stroke varies inversely with the stroke required and directly with the output torque required.

From your description of the problem one solution can be from a crank, a link and a slider.  The crank would rotate 360 degrees and when properly to the slider by a link you would get the linear reciprocal motion from which the 3/8" rod actuated by the slider  can rotate back and forth 50- 60 degrees.

Just got back in the office...

Gentlemen (and ladies as applicable),

Thanks for all your input! Cockroach, it was scary reading your response. While out of the office I had our prototype shop start fab'g parts with virtually the same methodology / design as you describe. The valve will still have slight vertical motion (a function of the helical slot slope?) however primary motion will be rotational.

Thanks again for the inputs...

Rampower