Why was the piston reg invented?

[Eric Sedletzky]

My curiousity got peaked reading another thread about grease packing piston regs, the grease used, etc.
Why was the piston reg invented in the first place?
What was wrong with the diaphragm design that sherwood had and sold to Aqualung to make the first double hose?
I thought diaphragm regs were better for cold water, environmentally sealed, contaminants and salt can't get past the diaphragm and so the movable part just does it's thing without an o-ring and grease.
It seems to me that the piston is a higher maintenance pig than diaphragms requiring more tear downs, replacement of o-ring kits, re-lubing/packing, and they need more doctoring up to be used in cold water and dirty environments.
Plus I see an possible eventual problem in that where the piston slides in the barrel could there be a wear pattern that develops belling out the barrel in the area that the piston moves, especially if the reg was used a lot in gritty/silty environments.
I know that very fine sand, beach diving, and piston regs don't get along.
I'm failing to see the benefits of a piston reg other that the piston has virtually unlimited room to move thus allowing huge volumes of air to move though the reg based on demand. There was an ad I remember that said 30 divers could breathe off one manufactures piston reg.
These days however with newer state of the art materials and larger diameter and more flexible diaphragms, those regs can move plenty of gas to accomodate a gang of divers drawing off the same reg at deep depths.

Am I missing something?
Or is this a Ford and Chevy thing?

 

[tbone1004]

piston is a simpler design, cheaper to make, cheaper to repair if you don't pack them which the originals weren't. They also flow much more air than the original designs and I believe were easier to balance. So that's why they started, why they are still sold for anything other than O2 use, I don't get, but that's personal preference and clearly all the engineers at Scubapro and Atomic still think so.

 

[Divetech99]

Anecdotally? In the 50s, Cousteau (US Divers) invented the diaphragm reg, patented it and cornered the U.S. Market. Scubapro (in its beginnings) came up with the piston reg as a way to enter the regulator market. The rest is history.

 

[ams511]

One reason could be to get around Aqualung patents. Another could be that at the time piston regulators had some advantages: For example it is simpler design and flows more air than a diaphragm first stage which was more important with the downstream second stages of old. Also the main advantages of diaphragm regulators are cold water (under 45 degrees) and contaminated water. Most divers especially vacation divers will never care about this.

---------- Post added February 14th, 2015 at 08:57 PM ----------

Anecdotally? In the 50s, Cousteau (US Divers) invented the diaphragm reg, patented it and cornered the U.S. Market. Scubapro (in its beginnings) came up with the piston reg as a way to enter the regulator market. The rest is history.

Scubapro was an offshoot of Healthways after they declared bankruptcy. I think originally they were selling Beuchat designed regulators until their own designs were ready.

 

[ajduplessis]

Because they perform very well. MK25 for deep dives, mk2 for last deco and anything in between.

 

[Nemrod]

Higher potential performance (flow rate), rotating turrets for optimal hose routing and up or down mounting, failsafe unlike diaphragm, simple and stable. A classic regulator battle would be the USD/AL Conshelf XIV diaphragm vs. the SP R109/MkV piston. N

 

[halocline]

There are two basic types of piston design, and they differ quite a bit. The flow-by piston, like the MK2, has the distinction of no dynamic o-rings being subjected to supply pressure, an extremely low parts count, and the resulting stellar record of handling abuse for years without maintenance.

The flow through design (MK5 et al) is also extremely simple and allows for balancing (well, almost balanced) without the complexity of a balance chamber, and flows a lot of air, with very stable IP and very quick recovery. When the MK5 came out, it's performance was outstanding and rebuilds were a breeze. Piston regs weren't always like the MK25 and atomic.

 

[Eric Sedletzky]

Anecdotally? In the 50s, Cousteau (US Divers) invented the diaphragm reg, patented it and cornered the U.S. Market. Scubapro (in its beginnings) came up with the piston reg as a way to enter the regulator market. The rest is history.

Cousteau technically didn't invent the diaphragm reg. Re
Diaphragm regs were already in use for years for high pressure cylinders in welding etc.
From my understanding Sherwood was around a long making reg systems for high pressure gasses, and Cousteau/Gagnan adapted that style of reg to be used underwater.
It just so happened to be a converted inert gas reg and that's why it's a diaphragm.

 

[Akimbo]

I'm not sure WHEN it was invented but am pretty sure it was long before Cousteau. Unbalanced and balanced flow-through pistons have been preferred for industrial regulators that require high flow rates for long time.

 

[chrisch]

....Why was the piston reg invented in the first place?....

The same reason as the unicycle - human ingenuity.