On Sun, 25 Dec 2016 18:44:58 +0000 (UTC), Frank Baron advised:

What does "urging" the clutch pedal mean?
(And what is this "treading" force?)

Everyone with a Toyota-4Runner 3rd-generation manual transmission and
similar Toyota Tundras and Toyota Tacomas has a problem that a certain tiny
plastic bushing invariably fails within a year or three in the clutch pedal
double-helix torsion spring return apparatus.
http://i.cubeupload.com/eXICt7.jpg

The "repair" costs upwards of $150 for parts alone, simply because the
clutch pedal bracket assembly and the pedal itself are usually toast, even
though the three tiny P & Q bushings costs only five bucks each and the
spring itself is only about double that.
http://i.cubeupload.com/54UwZW.jpg

We have already redesigned the clutch pedal return assembly but what we're
now trying to figure out is WHY Toyota used such a complex torsion spring
mechanism when our redesigned linear tension spring seems to work fine.
http://i.cubeupload.com/pSB77I.jpg
http://i.cubeupload.com/8lgaVh.jpg

My problem, right now, is just *understanding* the patent description:
https://www.google.com/patents/US4907468
http://i.cubeupload.com/wYA3iD.jpg

"The present invention relates to an apparatus for reducing the treading
force required to operate a pedal, such as the clutch pedal of an
automobile. More specifically, the present invention relates to an
improvement of the means for urging the pedal."
http://i.cubeupload.com/gMfTU7.jpg

Given they talk about both a two-spring and one-spring setup:
http://i.cubeupload.com/wYA3iD.jpg

But our setup is clearly just one spring:
http://i.cubeupload.com/WYoC8J.jpg

what specifically do you think they mean by "urging" and "treading"?
http://i.cubeupload.com/2Bsddp.gif

Restating the question to ask if anyone here can tell us what the patent
says about the single-torsion spring setup...

The problem everyone with a clutch has on 3rd-generation Toyota 4Runners,
Tacomas, and Tundras is that the Toyota dealer seems blissfully unaware of
the clutch pedal squeak root cause during the warranty period.
http://i.cubeupload.com/62kbRS.jpg

So the dealers simply grease the $5 nylon P bushing and delron Q bushings,
but by the time the squeak occurs, the $100 clutch pedal P-tab groove is
already starting to be destroyed, eventually taking with it the $100 clutch
pedal bracket holding the two $5 Q bushings.
http://i.cubeupload.com/eXICt7.jpg

So most of us have redesigned the Toyota clutch-pedal return assembly to
remove the extremely complex (geometrically) torsion spring and replace it
with a far simple linear spring setup.
http://i.cubeupload.com/WO7trl.jpg

We've also redesigned the P and Q bushings, using better materials:
http://i.cubeupload.com/UMY0Vl.jpg

But they still fail within two or three years.
http://i.cubeupload.com/UnuX55.jpg

We're currently at the stage of trying to *understand* why Toyota engineers
used such a horrifically complex clutch-pedal-return mechanism, which we
need to know if we're going to assess the long-term impact of our redesign.
http://i.cubeupload.com/Y18Qdh.jpg

We only recently found the patent, which shows a mechanism almost exactly
the same as ours, so, at this point, we're just trying to understand the
patent wording with respect to the single-spring function because we have
been re-designing the single spring setup using a variety of methods:
http://i.cubeupload.com/TYHGRW.jpg

The reason it matters is that the patent shows both a two-spring and a
single-spring mechanism, where we presume the two-spring mechanism operates
in both directions while we can intuit that the single-spring mechanism
operates only in one direction.
http://i.cubeupload.com/wYA3iD.jpg

But is that the case?

We don't know, simply because we don't understand the language of the
patent. https://www.google.com/patents/US4907468

Do you?

Specifically, what is the patent saying the single-spring apparatus
accomplishes?