Note: Descriptions are shown in the official language in which they were submitted.
~ ~()2~
CO~POSITE MULTILEAF, MULTISTAGE~ LEAF SPRING
This invention relates to vehicular suspension. More
particularly, this invention relates -to a multileaf vehicular
spring which has a light weight leaf. The leaf comprises
about40 to 75%by volume filamen-tary solids of a first modulus
and a remainder comprising continuous organic solid of a
second, lower modulus.
Multileaf vehicular springs are known. See, for
e~ample, U.S. Patent 2,052,062; 3,292,918 and 3,493,222.
Moreover, sprinys comprising leaves which contain filamentary
solids in an organic solid are also known. See, for
example U.S. Patents 2,600,843; 2,829,881 and 3,142,598.
The spring of this invention differ from those in such
patents in that it is a multileaf, multirate spring
that has a discrete, pultruded, secondary leaf having
filamentary solids densely packed in certain fashion
throughout a continuous organic solid.
; This invention relates to a vehicle leaf spring.
The spring has a light weight leaf. The leaf comprises
a pultruded beam with about40 to 75%(preferably about
50 to 60% by volume filamentary solids and a remainder
fraction (preferably about60 to 29% more preferably about
50 to 40%by volume) oE continuous organic solid. The
organic solid binds together the filamentary solids.
At least about 80% (more preferably, at least about
90%) by weight of the filamentary solids comprises a
multitude of discrete, tensilely stressed, filamentary
solids, densely packed substantially uniformly throughout
the organic solid. These discrete, tensilely stressed
and densely packed, filamentary solids coextend the
beam longitudinally in a plurality of planes that accept
tensile or compressive stress, respec-tively, upon a
flexure of the spring that bends the beam. Up to about
10% by weight of the filamentary solids comprises randomly
oriented filamentary solids in a mat on a surface of
the beam that receives longitudinal compressive stress.
~. ~ ' Ai,
~3
~ 3~5~
In preferred embodiments, the beam has between
about 50 to 60% by volume glass fiber and more preferably
more glass than organic solid by volume. Up -to about
iO% by weight of the filamentary solids comprise woven
filamentary solids that have fibers oriented across one
another substantially in a plane of the aforementioned
planes. In certain embodiments, the beam has a configuration
that is substantially straight along a longitudinal axis
without the aforementioned flexure. The beam has a cross-
section that is preferably substantially rectilinear.
In an especially preferred embodiment, thisinvention relates to a multirate, multileaf vehicular
spring. In such spring, a first leaf (normally a set
of leaves comprising a first leaf) acts independently
of a second leaf under a first load; but it acts together
with the second leaf under a second load which is greater
than the first load. The first leaf has ends adaptable
to attach the spring to a vehicle at first and second
vehicle locations. The second leaf has a center section
bindable with a center section of the first leaf to the
vehicle at a third vehicle location. The third vehicle
location is between the first and second vehicle locations.
The improvement of the invention with respect
to such a multirate spring comprises a second leaf that
is a light weight leaf. The light weight leaf comprises
a beam, preferably straight, that has about 40 to 75%
(preferably about 50 to 60%~ by volume filamentary solids
of a fir~t modulus. A remainder fraction (preferably
about 60 to 25%, more preferably about 50 to 40% by volume)
comprises continuous organic solid of a second, lower
modulus. The organic solid (e.g., vinylester or polyester
or epoxy thermoset resin) binds together the filamentary
solids. At least about 80% (preferably at least about
90~) by weight of the filamentary solids comprise a multi-
tude of
,, . ~
32S~
discrete, tensilely stressed fllamentary solids, densely
packed subs-tantially uniformly throughout the organic
solid. These discrete, densely packed and tensilely
stressed, filamentary solids coextend the beam longitudinally
in a plurality of planes that accept tensile or compressive
stress, respectively, upon a flexure of the spring that
bends the beam. The beam in these especially preferred
embodiments is preferably substantially straight under
the aforementioned first load. The beam preferably
has a configuration that has a substantially rectilinear
cross section. The beam also has a preferred glass
content as well as random and woven filamentary solids
as noted hereinabove.
The invention is described further, by way
of illustration, with reference to the accompanying
drawings, in which:
Figure 1 illustrates schematically operation
multirate spring 150 in accordance with this invention.
Configurations I, II and III denote spring conditions,
somewhat exaggerated for purposes of illustration,
under increasingly larger loads;
Figure 2 illustrates graphically spring
rates for multirate spring 250 of Figure 3, the ordinate
being load in newtons and the absissa being spring
height in millimeters;
Figure 3 illustrates multirate spring 250
of this invention, main leaf 157 appearing in flat
main leaf condition;
Figure 4 illustrates the spring of Figure
3 looking in from II - II of Figure 3;
Figure 5 illustrates the spring of Figure
3 looking in from III - III of Figure 3;
Figure 6 shows spring seat 400 upon which
a spring such as in Figure 3 may mount, the curvature
shown as 402 accepting an axle member;
Figure 7 shows another view of spring seat
400 of Figure 6, this view looking up into the seat
from a position of the axle, with the U-bolts having
sections 410 and 412, respectively, that are part
of a U-bolt assembly;
5~
Figure 8 is another view of spring seat 400
of Figure 6; and
Figure 9 is a cross-section of beam 101 of Figure
4 that illustrates composition with respect to continuous
5 and discrete filamentary solids.
This invention re;ates ~o leaf springs comprising
a light weight leaf. In p-eferred embodiments, the spring
is a multileaf, multirate spring comprising a second stage
leaf that is a pultruded beam. The beam in these embodi~ents
10 preferably has an unloaded configuration that is substantially
straight.
Figure 1 of the drawings schematically illustrates
operation of multileaf, multirate composite spring 150
of this invention~ Spring 150 has main leaf 156 and other
15 leaves 152 and 154. The composition of leaves 152, 154
and 156 is steel. Spring 150 additionally has leaf 100.
Leaf 100 comprises glass fibers in a thermoset matrix.
Configuration I of Figure 1 shows multirate spring
150 under a first load. Spring 150 conforms to configuration
20 I, when, for example, a vehicle carrying it is unloaded,
e.g., "curb position".
Configuration III of Figure 1 shows multirate
spring 150 under a second load, greater than the first
load. Spring 1~0 conforms to Configuration III, when,
25 for example, a vehicle carrying has a capacity load, i.e.,
"normal load".
Configuration II of Figure 1 shows multirate
spring 150 under a load intermediate between the first
and second loads. In Configuration II, spring 150 is
30 in transition between first and second spring rates. The
first spring rate has contributions from leaves 152, 154
and 156. The second spring rate has an additional con-
tribution from leaf 100.
~.~
~fL~25~
Configuration II of Figure 1 shows main leaf 156
without camber. This position is commonly referred to
as "flat main leaf". Flat main leaf may occur before or
after transition between first and second spring rates.
Figure 2 approximates graphically a load (y axis in
newtons) -- deflection (x axis, in millimeters) curve
for multirate spring 250 oE Figure 3. The deflection
measuremerlt corresponds to overall spring height~ The
spring is unclamped and mounted on rollers during
measurements.
The slope of line 200 corresponds to a spring rate
of multirate spring 250 when it is in a configuration
lLke I of Figure 1. The slope of line 202 corresponds
to a spring rate of spring 250 when it is in a
configuration like III of Figure 1. The intersection of
lines 220 and 202 represents a transition between the
spring rates.
~ emarcation 202 approximates flat main leaf
c~nfiguration for multirate spring 250. Flat main leaf
of spring 250 occurs before transition because spacer
180 (Figure 3) delays engagement of leaf 101 with the
other leaves.
Figure 3 shows with greater particularity an
embodiment of this invention. Multirate spring 250 has
a set of leaves 153, 155 and 157; leaf 157 is the main
leaf. Leaves 153, 155 and 157 comprise steel; they give
spring 250 a first spring rate. Spring 250 has
additional leaf 101. Leaf 101 comprises glass fibers in
a thermoset matrix; it gives spring 250, with leaves
153, 155 and 157, a second spring rate.
Main leaf 157 of multirate spring 250 has "eyes"
140 and 160. Eyes 140 and 160 comprise integral
curvatures 162 and 142 of main leaf 157. Eyes 140 and
160 contain press fitted bushing material 144 and 164,
respectively. Within press fitted bushing material are
metal sleeves 146 and 166, respectively. Spring 250
mounts to a vehicle through sleeves 146 and 166 at firs-t
and second vehicle locations, i.e. (a) -the chassis or
body on either side of the axle or (b) the axle at
5~
spaced locations. Sleeves 146 and 177 mount,
respectively fixedly and translatably at spaced vehicle
locations. Thus, as leaves of multirate spring 250
flux, multirate spring 250 has an end that translates
upwardly or downwardly at the translatable mount (e.g.,
shackle).
Clip 170 of Figure 3 holds leaves 153, 155 and 157
together; i-t prevents excessive splaying of leaves 153,
155 and 157. An additional clip (not shown) may also
10hold leaves 153, 155 and 157 at a corresponding,
opposite end portion of multirate spring 250. Spring
50 of Figure 3, mounts fore and aft of the vehicle
axle. Clip 170, which is forward of the axle, thus
prevents entry of gravel or other particulate between
15leaves 153, 15S and 157, particularly during
acceleration of the vehicle.
Fastening means 190 of Figure 3 extends through
leaves 153, 155, 157 and 101; it permits alignment of
spring 250 in spring seat 400 of Figures 6, 7 and 8.
20Fastening means 190 also extends through spacer 180 as
shown more particularly in Figure 4. Spacer 180 delays
engagement of leaf 101 beyond "flat main leaf" condition
of main leaf 157. Spacer 180 comprises aluminum but may
be any other such formable material.
25Figure 4 is a section taken of multirate spring 250
looking in at II-II of Figure 3. Fastening means 190,
as shown, comprises threaded bolt 19 having cap 196 and
nut 194. Bolt 192 fits snugly in orifice 198 of leaves
153, 155 and 157 and orifice 102 of leaf 101. Cap 196
30fits into orifice 408 of spring seat 400. Spacer 180 of
Figure 4 has integral creep resistors 182 that wrap leaf
101. Leaf 101 has curvatures 104 that fit snugly into
the intersection of spacer portion 184 and creep
resistance portions 182 of spacer 180. Creep resistance
35portions 182 of spacer 180 resist creep of leaf 101
during operation of multirate spring 250.
Figure 5 shows a cross section of clip 170 lookiny
in at III-III. Rivet 172 fits tightly into orifices 172
- and 174 of clip 176 and leaf 153, respectively. The
5~
head of rive-t 172 maintains enyagement of cllp 176 with
leaf 153.
Figures 6, 7 and 8 show side views and a bottom
view (looking up from the axle) of spring seat 400.
Seat 400 comprises a top, flat portion 406 upon which
multirate spriny 250 rides. Flat portion 406 has a
width equal or slightly greater than the width of leaf
101; it has a length about two times its width. Seat
400 has orifice 408. Bolt head 196 fits into orifice
408.
Spring seat 400 has curvature 402. Curvature 402
mirrors axle housing (not shown) curvature. Nubs 420
interrupt curvature 402. Durinq assembly of multirate
spring 250 to a vehicle, nubs 420 provide metal that
welds seat 400 to the axle housing. Nubs 420,
accordingly, disappear during welding operation.
Spring seat has an external curvature shown by 404
in Figures 6 and 7. Curvature 404 slopes away from flat
portion 406. Thus, flat portion 406 exists as a plateau
upon which multirate spring 250 rides. The plateau
provides smooth engagement between beam 101 and seat
400.
Figure 8 is a view of spring seat 400 looking up
from an axle position. Figure 8 shows sections 410 and
412 of members of U-bolt assemblies. The U-bolt
assemblies are conventional; they wrap around the axle
housing. They engage a single plate above leaf 157 of
Figure 3.
Figure 9 illustrates a section of leaf 101. The
section is substantially rectilinear with corners having
a small radius. Leaf 101 comprises filamentar~7 solids
in a continuous organic solid.
Figure 9 illustrates material composition at a
cross-section of leaf 101. Sections 500, 502 and 510 of
leaf 101 show relative position and character of
filamentary solids in thermoset matrix 504. Sections
500, 502 and 510 extend the length of leaf 101.
Leaf 101 has about 54~ by volume filamentary solids
which comprise glass fibers; the remainder of leaf 101
5~
is a continuous organic solid (thermoset polyester
esin) that binds the filamentary solids toge-ther.
Leaf 101 of Figure 9 has been made by a pultrusion
process~ In the pultrusion process, pullers draw resin
coated filaments through a heated die. The resin
hardens in the die. Examples of pultrusion processes
appear in U.S. Paten-ts 4,1S4,634; 3,853,656; 3,793,108;
3,68A,622; 3,674,601; 3,530,212; and 2,741,294.
Leaf 101 of Figure 9 has three orientations of
filamentary solids. Greater than about 95% by weight of
the filamentary solids comprise a multitude of discrete,
tensilely stressed, filamentary solids densely packed
substantially uniformly throughout thermoset polyester
504. These densely packed, tensilely stressed,
filamentary solids coextend leaf 101 in a plurality of
planes. The planes receive tensile or compressive
stress upon flexure of multirate spring 250 (Figure 3)
that bends leaf 101. Ends of a portion of such
tensilely stressed solids appear as 510 in Figure 9.
(Ends 510 are slightly enlarged relative to the
remainder of leaf 101. Also, ends of other of these
filamentary solids, substantially uniformly dispersed
throughout leaf 101, have been omitted from Figure 9 for
clarity.)
Less than about 2% by weight of the filamen-tary
solids of leaf 101 comprises randomly oriented
filamentary solids. Portion 502 in Figure 9 shows
position of these randomly oriented filamentary solids
in leaf 101. The randomly oriented solids form a mat
(e.g., glass fiber mat) on a surface of leaf 101. The
mat side of leaf 101 rests on spring seat 40C in
multirate spring 250 of Figure 3. (Portion 502
exaggerates for purposes of illustration the relative
volume taken by the randomly oriented filamentary
solids. The mat of leaf 101 is actually only a few
glass fibers thick.~
Less than about 2% by weight of the filamentary
solids in leaf 101 comprise a weave of filamentary
solids. The weave is held tightly within the above
5~
noted multi-tude of filamentary solids. Portions 500 of
Figure 9 illustrate positions of the weave ln leaf 101.
The weave has filamentary solids positioned across one
another. The weave contains fibers -that are transverse
to -the long dimension of leaf 101. These transverse
fibers reduce creep of leaf 101 in multirate spring 250.
(Portions 500 exaggerate Eor purposes of illustration
the relative volume taken by the weaves. Each weave in
leaf 101 is compressed such that it has a volume that is
about 1 or 10 fibers thick in a cross section cf leaf
10 101. )
The weave of filamentary solids in leaf 101, as
mentioned, reduces creep of leaf 101 in multirate spring
250. In an alternative embodiment of multirate spring
250, leaf 101 comprises such weave but omits spacer
creep resistors 182 shown in Figuxe 4. In this
embodiment leaf 101 and leaves 153, 155 and 157 have
equal widths.
In still other embodiments, leaf 101 is as above
described with respect to continuous and filamentary
solids, but, when unloaded, has camber. In a multirate
spring embodiment, such a cambered leaf may engage
leaves 153, 155 and 157 before or after flat main leaf
position of leaf 157 in Figure 3, depending, for
example, on whether leaf 101 has a positive or negative
curvature with respect to leaf 157. In still other
multirate spring embodiments, such a cambered leaf is a
leaf of the first set of leaves as well as the second
stage leaf.
