Not my field, but the following can be found on the Yamaha website:

YTR-9636
Caractéristiques techniques
"potence, 1ère et 3ème coulisses d'accord pour Mib ou Ré"

http://fr.yamaha.com/fr/products/musical-instruments/winds/t...

YTR-9636
Specifications
"Interchangeable main tuning slides and 1st and 3rd valve slides for D"

http://usa.yamaha.com/products/musical-instruments/winds/tru...


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Note added at 1 hr (2012-02-22 17:55:40 GMT)
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On the other hand, returning to the simple tube bend theme, I have also found the following:

"OLD ENGLISH INSTRUMENTS OF MUSIC

The advantage which the longer tube gave for the
elaboration of fanfares was not lost sight of by the trum-
peters. The objection which might naturally be urged
against their use was that they were extremely awkward
to carry. So about the year 1300 we hear of " crooked "
horns {cors crogus), and from that period we date the step
which was destined to give the Trumpet its high place in
the realm of music as well as of pageantry. This step
was the folding of the tube by means of a U-shaped
elbow or potence, requiring, it is true, careful workman-ship, but at once securing unlimited length without loss
of portability. It is interesting to find that, as with the
making of a cylindrical tube, so with its folding into a
more compact form, the Romans had been in advance
of mediaeval Europe ; for on the walls of the House of
the Gladiators at Pompeii there is a fresco of the first
century a.d. which shows that a trumpet, very similar
in shape to our modern military instrument, was in use
in classical times."

http://www.ebooksread.com/authors-eng/francis-w-francis-will...

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Note added at 1 hr (2012-02-22 18:06:53 GMT)
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Also of potential interest is an article which cannot be accessed in full without a subscription, but which contains the following tantalizing snippet:

The Cornet and Other Brass Instruments in French Patents of the First Half of the Nineteenth Century

"...The internal valve tubing (called potence) is composed of a fixed part and of a mobile part operated by a vertical rod. This internal tubing has ..."

http://www.jstor.org/pss/25163859
http://www.jstor.org/stable/25163859