ECROU PRISONNIER A CRANS DE CALAGE AUTOMATIQUE

FREE SPINNING LAMINATED NUT WITH AUTOMATIC LOCK

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The invention provides a caged nut comprised of
stacked conical spring segments that automatically and
positively self-locks when tightened to a selected
pre-loading, without adjustment. The nut is free running
until seated, and the automatic lock mechanism ratchets
freely with respect to the cage while the nut is being run
down to its sealed position. Reverse rotation of the cage
is prevented, however. A ratcheting element in the
automatic lock mechanism allows the nut to be tightened by
free rotation in the "on" direction but the ratchet
prevents rotation in the "off" direction. At whatever
value of preload desired, the nut is tightened to the
extent necessary to provide that pre-load and the
automatic lock mechanism will lock it positively in that
position. The invention also includes a caged nut having
stacked conical spring washer segments in which the
segments are so formed as to provide a more uniform thread
loading, over the entire length of the threaded portion of
the segments. The invention further includes a caged
free-spinning nut characterized by a prevailing tongue
resisting counter-rotation having at least two washer
segments in which one of the segments is formed of a
material which takes a permanent set upon loading and the
other segment is formed of a material that returns
substantially to its original form following release of
the loading force.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a caged free-spinning nut having at least
two washer segments, the improvement which comprises forming
at least one of said segments of a material which takes a
permanent set upon loading and forming at least one other of
said segments of a spring material that returns substantially
to its original form following release of the loading force.
14

Description

~59830 1 ~
`..
BACKGROUND OF THE INVENTION
Free spinning lamina~ed nuts utilizing lamina-
tions o~ hex shaped hardened coned-clisc springs, formed as
a helex or tapped to match the bolt threads are known in the
prior art. Such nuts (sold by Peterson-American Corporation
under the trademark "Elephant" nuts~ have stacked aligned multi-
ple threaded discs retained by a steel outer hex shaped cage.
Wrenching dimensions may conform to standard SAE-IFI sizes.
These nuts are free running until seated. Locking
load is applied by additional rotation after seating, which
compresses and partially flattens the conical spring discs with
resulting mechanical interference on the thread flanks due to the
change in hole size as the conical disc flattens. This results
in thread interference that resists unloading that might other-
wise occur as a result of vibration. Thus, the independently
loaded conical spring threaded segments when flattened create a
thread interference that tends to lock the nut against rotation~
or loosening, when subjected to vibration.
As compared to other free spinning locknuts, these
nuts effeet a dimensional change under loading. Theyhave a
conical spring action that enables them to be counter rotated
over half a turn or 60 without loss of total load or loss of
- inter~erence.
However, the prior art laminated nut, described above,
requires for positive locking a secondary operation of adjustment
to align holes for co ter key insertion, wiring, or requires
mechaniral nut deformation into ~ slot ~r reeess. Further,
in the prior art, the loading on the threads of the nut segments
in non-uniform, to ~e extent uch that the stress is concentrat-
-2-

1~53830
ed in the first thread adjacent the bearing surface. At that
point the stress may be as much as 200% or more higher than
the average 6tress in the remaining threads.
: S
SUMMARY OF THE INVENTION
According the present invention, the above referred
to disadvantages of the prior art Elephant nuts are eliminated,
and a new combination of elements is provided which forms a
caged laminated nut that aùtomatically and positively self-locks
when tightened to 2 selected pre-loading, without adjustment.
The nut is free running until seated 3 and the automatic lock
mechanism ra~chets freely with respect to the cage while the
~ 15 nut is being run down to its seated position. Reverse rotation
; of the cage is prevented, however, A ratcheting element in
~ ~ the automatic lock mechanism alIows the nut to be tightened
; by free rotation in the "on" direction, but the ratchet prevents
; rotation in the "off" direction. ~t whatever value of pre-load
desired, the nut is tightened to the extent necessary to provide
that pre-load and the automatic lock mechanism will lock it
positively in that position without "backing or filling" neces-
sary to cotter key locking.
To back off or remove the nut, a tool is required
to unlock the locking elements of the automatic lock, ~nd only
then can the nut be rotated in ~he loosening direction.
The invention also includes a new laminated nut having
staeked conical spring washer segments in which the segments
are so formed as to provide a more uniform thr~ead loading,
over the entire leng~h o ~he ~hreaded portion of the segments,

lzsssao
as compared to the prior art laminated nut referred to above.
According to the invention the load/deflection ratio of at
least one of the conical spring washer seg~ents is made greater
for another spring segment. Preferably the segment next to
the load surface is m~de with the larger load/deflection rati~,
for example by making that segment of greater thickness than
the other spring washer segment. When the segment nearest
to the load is thus made of increased load/deflection ratio
then another of the spring washers of lesser thickness, then
the washer of greater loadJdeflection ratio will deflect at
a smaller rate than the other conical spring washer and when
the nut is fully tightened will take up or absorb a greater
portion of the total stress than otherwise would be the case.
This causes the load to be more evenly distributed among the
threads of the various laminated spring washer segments ~nd
tends to eliminate or reduce failure by successive (i.e., one
after another) thread stripping or by shearing of the bolt.
":"
- BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of the drawings is 8 side view, partly in
section, of a spindle for a front drive automobile in which
the tapered roller bearings are pre-loaded to a selected value
by an a~tomatic locking caged laminated nut constructed in
accordance with ~he pr~sent invention.
Figure 2 is a plan view of the automa~ic locking
nut of Figure 1.
Figure 3 is a sectional view along the lines 3-3
of the nut in Figure 2.
~igure 4 is h side ~iew of the nut of Figure 2.

3L~5~330
:::
Figure 5 is a plan view of the ratchet plate of the
automatic nut locking mechanism.
Figures 6 and 7 are partial views showing the operation
of the ratchet lock mechanism.
Figure 8 is a view, similar to Figure 3, of a modifi-
cation of the caged laminated nut of this invention, incorporat-
ing means for loading the threads of the conical spring segments
more uniformly than was the case in prior srt laminated nut.
In Figures 3 and 8 it will be noticed that, for conve-
nience, the outer edges of the washers are shown to be cylindri-
cal. In actuality each of these surfaces would be slightly
~ conical.
-; Figure 9 is a graph comparng the effect of relaxation
-~ or dimensional changes on a olid nut with the effect of ~uch
changes on an Elephant nut. The nut size illustrated is M20 X
1 .5 .
~igures 10, 11 and 12 show a tool, or fixture for
disengagement of the nut lock for removal of the nut.
DETAILED DESCRIPTION
.,,.
A particularly important application of the preRen~
~ invention is for spindles for front wheel drive automobiles.
-~ Figure 1 shows such a spindle 10, including tapered roler bear-
ings 1~,14 which must, for proper operation, be pre-loaded
to a selecte~ value and then maintained pre-loaded at that
value for long peri~ds of operation, including operation while
6ubject to vibration and shock.
A spindle nut for pre-loading said bearings and main-
taining the pre-~oad during operations of the automobile, con-
structed aceo~ding to the present invention, is shown at 18.
After assembly of the spindle components, nut 18

-
~ 330
is run down freely~ either by hand or by tool, on the threaded
end portion of the spindle bolt ~ until it 6eats against a
washer which transmits ~he force to a collar or wheel hub splined
to the spindle at 16. The collar in turn transmits the pre- -
loading force to the tapered roller bearings 12,14. Such forcemay be, for example, of the order of magnitude of 5000 psi.
After the spindle nut seats, it is tightened by a
wrench until the orce it applies to the bearings is increased
to the selected pre-loadlng value. The spindle bolt is placed
in tension, and the tapered roller bearings are pre-loaded
in compression. Tightening of nut 18 creates this tension
- and compression, to a degree determined by the nut tightening
torque. The total clamp load generated by the nut is in the
magnitude of 17,000 to 22,000 pounds.
The "turndown" of nut 18 will seat the bottom face
of the nut flatly against the flat top of the washer on which
it bears. It also, after it seats, will partially flatten the
conical spr$ng washer segments 40,42,44,46 ~Fig. 3) and thereby
create a spring force which gradually increases as the segments
become more and more flattened, i.e. as they approach their
planar position. The design is such that when the nut is fully
i,.
tightened the conical spring segments are still not completely
flat,bu~ still have some bow. A typical bolt load design will
~ flatten the conical ~ring w~shers by 60/70~/o~ They are not
;~ 25 entirely fl~tened.
~ the nut 20 is tightened, ratchet lock 32, as shown
in Figures 2,3,4,5,6, and 7, will ratchet, with the lugs 34
being freed from the locking slots 26 in cage 22 as the cage
! iS rotated clockwise. The ratchet lock has four fingers 36
integral therewith, composed of spring steel just ~s is the

~i ~X~ 0
case with Lhe conical spring segments. These four fingers
act to center the nut on the bolt and, in addition, one of
them drops into and engages a slot 38 in the side of the spindle
bolt and thus locks the ratchet plate 32 to the spindle bolt
against relative rotation, just as soon as the nut is rotated
on the bolt by as little as ~ of a turn. When this happens,
the ratchet plate 3~ in effect becomes locked to the spindle
20. However, the nut itself can still be rotated (tightened/or
loosened dependin~ on the direction_of rotation,) by the ratchet-
ing action shown in Figures 6 and 7 as explained above, simplyby turning cage 22 with a socket wrench which in turn rotates
the conical spring segments 40,42,44 and 46 in somewhat the
same manner (until they are seated) as a solid nut is run down
-- on a bolt.
:~ 15 The nut can thus be tightened, to the position in
which it exerts the selected preload force on bearings 12,14
and then will be automatically locked by one of the lugs 36
being engaged in slot 38 in the side of the bolt. No backward
rotation is necessary to form that lock, at exactly the desired
pre-load Ratchet 32 and lugs 34 thereon enable the nut to be
tightened to exactly the desired pre-load and then hold the
nut in that position.
In the ratcheting operation, during run down of the
nut 18, there must of course be some provision made to allow
lugs 34 to disengage from the slots 26 in cage 22. This is
provided by forming slots in the sidewall of cage 22 a~ each
cor~er of the hexagonal cage. Such slots allow each side wall
to flex be~ween the slots, and about the lower corner as a
hinge, thus allowing the cage to free itself from lugs 34 as
the cage is ro~ted clockwise relative to the spindle bolt

~2~9~
and ratchet lock 32.
Thus there is formed a new automatic and positive
lock which reguires ~nly tightening of the nut with the usual
wrench. Once in place and locked in the desired position,
it simply won't come loose, regardless ~f vibratlons, and fully
; meets presently known pr~duct liability requirements.
The use of this lock is of course not limited to
laminated nuts. It may also be used with solid nuts. It has
particular utility however for lock nuts for spindles for front
drive automobiles where a high degree of preci~ion and at the
~!~ same time positive safety i~ required.
As previously stated, all parts of the lock nut of
this i~vention can be made of spring æteel or other ~pring
material and the ratcheting action in the embodiment shown is
provided by flexing of the side walls of the nut. However, the
flexing need only be very slight and it is found in practice that
the usual socket wrench tolerances are sufficient to allow the
socket head to fit over the nut, and to rotate the nut, with
ratcheting action and consequent side wall flexing without bend-
~;~ 20 ing. In fact, the flexing walI action tends to hold the socke~ or
,
- the nut until it is tighteened to the point where the ~atchet
locks in f inal position and the socket is to be removed.
; In the embodiment shown, twelve lugs 34, and 6 slo~s
26 are provided~
The load bearing components of nut 18, as shown in
Figures 2 through 7, consist of four conical wa her 6pring
~egments 40,42,44 and 46 which are stacked and aligned to form
in efe~t a laminated nut.
It ~hould be noted that the combination shown of
the ratchet with self ~eeking fingers provides ~n entirely

LZ59830
new result, o~ substantial commercial advantage. The job not
only can be done better, but also cheaper.
The angle used for each cone shaped spring segment
can be calulated by a formula disclosed in Schnoor's Disc Spring
~:~ S Handbook, pages 12-17. As previously stated, the spring discs
are not calculated completely to flatten under the designed
load; they fle~, ~o~h up and down as the bolt elsngates, con-
: tracts, or vibrates.
Figure 9 compares the results obtained from a solid
nut shown at the left of the Figure and so marked, with the
results obtained from a spring disc laminated nut with cone
spring segments. As will be seen, the bearing pre-loads are
maintained over wide ranges of deflection for the conical spring
disc laminated nuts (the two right hand curves) as compared
with the 9 solid nut in the left hand curves.
The formulas relating to loads necessary to flatten
cone-spring discs show that, other things being held constant,
the load to flatten will increase with disc thickness. This
, ~ principle is utilized in Figure 8 to provide a nut of greater
load carrying ability because of more uniform thread loading,
. or increased ~atigue life, and of greater self blocking character-
istics.
In Figure 8 the bottom cone shaped spring washer
segment 72 is of about twice the thickness of the two other
~egments 68 and 70. This results in a more even distribution
of the load, frorn bolt to nut, over the length of the threaded
sections 68,70, and 72. Thus the nut is less likely to fail
by shear of the bolt, stripp~ng of the threads, or by fatigue
failuse~. A substantial improvement resul~s with no ~dditional
cost, simply by novel design.

~ 30
Three laminated segments are shown in Figure 8 but
v- less or more for example 2 or 4 could be used. The automatic
lock of Figures l through 7 also could be added to Figure
if desired.
Figures lO,ll and 12 show a tool, or fixture for
disengagement of the nut lock for removal of the nut. Pin
82 fits in the centering recess of spindle bolt 20 and an arm
84 extends therefrom over the edge of the bolt and under lug
36. Thus lug 36 is lifted out of slot 38, allowing it to be
turned, and removed, by a socket wrench which fits over outer
cage 22.
; Some modifications of this invention will of course
be obvious to those skilled in the art. In the embodiment
shown in the drawings the components, including the conical
spring segments, are made of heat treated spring steel as 8
preferred material. However, it is possible as a modification
of the preferred embodiment to provide a prevailing torque
characteristic ~interference after counter rotation), by incorpo-
rating a non heat treatable washer segment in the nut that
is permanently flattened by the nut loading. This feature
is significant to bearing applications that requlre bearing
clearance adjustment.
Previous designs of the Elephant type nut, prior
to the present inventor, used conical spring segments but
did not relate the ununiform nut loading of the segments to
functional deflection characteristics. The possible concen-
tration of l~ading, in ~ nut-~o~ thread fastening, nearly
two thirds of all ~ension loading occurs at the first thread
engaged. This uneven loading of previous multiple element
nut~ caused acceler~ted deflection of the first element. Th~

598;~0
results of this accelerated deflected element caused high stress
on the male threads of the bolt with possible thread shear
results. Nuts previously made in this manner and commercially
marketed would not meet SAE or IFI industry requirements for
S strength. It is an industry accepted practice that nut strength
shear requirements must exceed bolt tensile strength so that
the mode of failure is bolt breakag~e.
The present invention combines the industry established
formula used for predicting conical washer behaviour, ~Ref.,
page 13, Adolf-Schnoor "Disc Spring Handbook"~ with industry
proven load distribution characteristics in nut-bolt joint
applications. This combination used in association with other
nut bolt tolerance standards allows for design of spring washer
segments with predictable behaviour related to bolt loading.
.... .
The nut design as proposed is based upon near uniform washer
segment deflection and loading bottom to top.
With respect to the mechanically positive automatic
lock mechanism of the invention, the lock mechanism automatically
engages in a slot or groove or grooves in the associated bol~,
stud or shaft, which can be driven by hand or power tools to
~r desired torque or clamp load requirements, an~ is positively
.- locked from counter rotation. The combination of an automatic--
self seeking secondary lock mechanism and nut with predictable
load-deflection characteristics that contributes spring loadin~,
~ 25 allows fastener loading of precise joint preload with the torque
and clamp l~a~ tolerances of industry used power tools. This
combination is particularly adaptable to loading bearings that
; require defined preload. Further, the design of this invention
does not require any secondary adjustment for precise loading.
Further advantages of the present invention are (1)
''' :,' ,-' - ,

~59~330
.
the establishment of desi~n criteria that will produce uniform
deflection of the nut related to nut-bolt joint loading that
will provide predictable load-deflection and resultant inter-
ference for blocking. This combination will provide nut strength
relationships CQmmensurate with established industry standards.
The uniform loading of the nut top to bottom is accomplished
by varying the washer segment thickness related to loading.
The bottom washer with the greatest load would be the heavy
member with subsequent washers reduced in thickness. This
means that washer segment thickness can be thickness that is
greater than the pitch, more than a single pitch or less than
a pitch.; (2) the provision of a parallel load surface for
critical loading of joints that contain bearings. Heretofore,
the nut required grinding or special surface finishes related
to perpendicularity of the axis of the thread to provide uniform
interface loading. The resilient action of this invention
allows the interface surface to self seek for uniform loading.;
and (3) the provisicn of an inexpensive tool for ~he purpose
, of easily defeating the locking devise to facilitate removal
-~ 20 and reuse.
.~:
:~ ~ '
~::
~ , ~5
, ~ ~,
'

1~59~3~ !
OPERATING EXAMPLE
To illustrate the application of the invention to a
particular useS the following is an example of the automatic
nut lock as manufactured for use as the spindle lock nut of a
1981 Escort and Lynx Ford front wheel drive car:
Ford engineering specified load ME-900.10= 46,5001bs
Proof Load
Application - Front wheel spindle nut design load c
}7-22,000 lbs.
Assembly Torque 180-220 lb.ft.
Nut to have six threads with design dimensional stack
,~. tolerance to accomodate five threads minimum.
Nut Construction:
-' 15 Conical spring washer elements, .078" thick with crownof .050", material 1065-1070 spring steel, ratchet
locking mechanlsm and cage - also spring steel. Cage
is .036", Lock Mechanism is .040 thick.
Application Description:
~- 20 Spindle nut to be hand started, driven by Rockwell
;, Tool at 125 RPM. Locking Mechenism to self 6eek lockin~ ,
;l slot and ratchet free to design clamp load.
The sample spindle nut described above does not incorp-
orate varied thickness conical spring washer element. This appli
~- 25 cation is utilizing less than 50% of the nut proof load capacity
-~ and is not susceptible to high shear loading.
,-
.... . ..