sectional thread

Because they used the same cap and bottle used in carbonated drinks. I'm taking a wild arsed guess but the segments are to allow controled venting of pressure like when your Pepsi is dropped from the top section of the vending machine, thus causing the carbonation to get upset.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Gerry :-)} London, Canada

Can't see the photo without signing up.

So it had a break-off tamper indicator ring at the bottom of the cap?

Maybe to make it easier to push the cap onto the bottle.

Best regards, Spehro Pefhany

Mainly so the parts can be molded without the need for a special "unscrewing" core.

By segmenting the threads it is possible to greatly simplify the mold construction. It also eliminates the parting line problem on the threads where the mold closes greatly reducing maintenance.

Unka' George [George McDuffee]

------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).

I sent the wrong link- sorry, here's the right one:

I think it's quite likely the threads are designed for fastest handling by the molding and filling automation. In particular, the blow molding machinery operates at very high rates. The preforms for the blow molders are injection molded in multi-cavity molds, so the cycle rates there are not too high. But I've seen blow molders running at something like 20 bottles per *second*. These were continuous motion machines, which means the preform, which looks like a little capsule attached to a bottle neck and thread, have to be screwed into a station on a carousel on the fly. The carousel on the fastest machines I've seen were 8-10ft in diameter and spinning so fast the individual stations were a blur. That interrupted thread would allow the preform to be mated up in a fraction of a turn rather than the couple turns required to remove the cap.

An animation of a single station:

It is so the cap does not go flying off from the pressure.

Google Patent number: 4747502, plus there are a few others.

MikeB

Eg. 6234338

Bingo! So as you unscrew the cap, the pressure can vent safely out through the slots, whilst the cap is safely contained on the bottle threads.

The security ring is screwed on with the cap-- just it has fingers that snap out into a groove in the neck and retain it, with far more strength than the bits that get torn when the cap is removed. I think I could make a tool to remove Dansani security caps without breaking them.

Thanks for this question-- I actually have taken a course in design of blow molds and this area was not covered (though there was endless discussion of 'starts' and such like). The standard thread forms are covered by a part of the SPI- the Plastic Bottle Institute, believe it or not.

Best regards, Spehro Pefhany

Da - just thought of the reason - we all had it right - but think:

If the bottle is high pressured - and you un-screw it - you want to vent the gas and liquid without blowing the top into someones eye or the like. e.g. wet hands but not broken eye cornea.

Mart> >> On Sat, 21 Mar 2009 22:28:21 -0700 (PDT), engineman

For years I've desperately wanted specifications for these threads. Where are they to be found? Can you bless me with them?

Does this help - it has been a book mark of mine for a while

That was what I was thinking when I offered my guess.

Wes