Talking about pl-s lamps, is it true what philips says in it's webpage that the "bridge technology" that Philips uses is better than bended technology used by others and it enables more light and higher efficiency or is this just marketing bs?
There are two things:
First the bridged tubes are along the whole length just straight tubes, so allow in an easier way to spread the phosphor coat more evenly (thus being closer to the optimum thickness across the whole surface).
The tubes bend in a sharp way are not that far from this either.
Second aspect is, the ends protruding behind the bridge serve as the lamp cold spot. That allows to use simpler "reverse stern" seal, but it's main advantage is the filaments could be closer to the lamp ends, what means with the same physical size the effective discharge could be made longer, hence more efficient. Then the lamps have two possible cold spots: One within the exhaust tube behind one of the electrodes (works when the lamp is base down) and second candidate for that cold spot are the tube ends behind the bridge (dominant mainly when the tube runs base up; in other positions both places somewhat work together)
The thing is, with bend lamps the filaments have to be pushed further inside the tubes, so the area behind the filaments could serve as the pressure regulating cold spot, even when the lamp is base up, so when the heat rises there.
Some makers went around this by making sharper shaped corners around the bend, which then become out of the arc way and so easily may serve as the cold spots (corners of the rectangular bends with Osram, "ear lobes" on the GE tubes,...).
So yes, if you compare it just to a plain bend, the bridge is more efficient. But when the maker precisely shapes the bend so it forms the required features, nearly equivalent effect could be gained with way simpler glass working process (just blowing the glass from the bend area into a proper mold).
But I think the bridge concept looks way "cleaner", at first glance there are just two cleanly glowing sticks.
What is interesting, when Tesla have made these lamps, they used similar bridge concept as Philips, but the technology of forming that bridge was clearly different (the bridge had different shape and even size).
