Todays patent is one of Dürr’s many U.S. patents assigned to Luftschiffbau Zeppelin.
My data base includes 31 U.S. patents issued to Dr. Dürr
(Dürr. Durr, or Duerr). Most were assigned to Luftschiffbau Zeppelin.
You can only search for these older patents (pre 1970’s) by
Patent Number or currently assigned classification(s) ) on the USPTO
You can find nearly half of them on Google.com/patents under:
Inventor (Dürr, Durr, or Duerr),
Exact Phrase (Ludwig Dürr) , or
Assignee Name (Zeppelin and Luftschiffbau Zeppelin).
Perhaps some of our members might be able to tell us how many German patents he held.
“Because of the ship having cars situated underneath its
hull or body the lower rudder will have less efficiency than
the upper one, both having the same surface and usually the
same shape. This causes a very undesirable effect on the ships
horizontal course, as the resistance from the rudder above the
hull or body will differ from the resistance of the lower rudder,
and this will have a rolling effect on the ship as a whole.
According to my invention I am doing away with these
drawbacks by horizontally extending the surface of the lower
rudder, so that it is wider than the upper one. Furthermore it
may be advisable to also increase the area of the lower rudder
by an adequate change in its shape. Also in accordance with
my invention it may be useful to provide means for always
giving the lower rudder a wider angle of deviation than the
upper rudder has at the same time. This for example may be
attained by making the operating levers of the lower rudder
shorter than those of the upper rudder while the control wires
of both rudders are moved over equal distances.”
NOTE: As chief engineer for Zeppelin throughout the Rigid Airship
era, Dr. Durr was responsible for the design and production of the
vast majority of all the world's rigid airships.
The USPTO neglected to cite the primary classification -
244/87 (Rudders and empennage). It might also have cited
244/125 (Airship hull construction).
Consequently, it ignored the purpose of the invention, to reduce
unintended rolling force and unwanted torque on the tail surfaces
of his huge rigid airships during turns and when operating in
cross winds. N.B. The patent addresses only two methods of
correcting the problem: Increasing the size of the lower rudder,
and/or increasing the angular displacement of the lower rudder
compared to that of the upper rudder.