Note: Descriptions are shown in the official language in which they were submitted.
CA 02720356 2010-11-05
SUSPENSION FOR A VEHICLE
Field of the Invention:
The present invention relates to a vehicle suspension.
Background of the Invention:
Suspensions for trucks and the like are well known in the art.
Indeed, a conventional vehicle suspension for connecting a wheeled axle to the
structural frame, or chassis, of a vehicle includes a combination of springs
and/or
shock absorbers mounted beneath the vehicle's chassis so as to absorb, isolate
and/or dampen the movements transmitted between the axle and the chassis.
Typically, a vehicle such as a truck will include a front axle supporting a
pair of front
wheels and at least one rear axle supporting a pair of rear wheels. It is also
known in
the art to provide a second front or rear axle to further increase the load
capacity of a
truck. Such a dual axle suspension is commonly referred to as a tandem
suspension.
Canadian Patent No. 2,070,859, issued January 10, 1995 to Simard and titled
"Tandem Axle Suspension for Vehicle", describes a front suspension for a truck
or
semi-trailer including front and rear tandem axles connected to a vehicle
chassis by
leaf springs.
It is also known to use inflatable air springs in conjunction with, or in
place of,
conventional leaf springs. In particular, it is known that air springs are
very effective at
absorbing vertical vibration and loads and as such air springs are often used
to
improve rider comfort. For example, U.S. Patent 6,382,659, issued May 7, 2002
to
Simard and titled "Load Distributing Tandem Suspension Assembly", describes a
tandem front suspension similar to that described above, with the addition of
an air
spring and shock absorber for supporting the second front axle in conjunction
with the
second leaf spring.
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Various disadvantages of air springs are also known. In particular, air
springs are
weak in shear and, as disposed in conventional vehicle suspensions, are
therefore
typically not well suited to absorb lateral loads experienced during
cornering.
Similarly, air springs deployed above an axle in a conventional suspension are
not
well suited to take moment loads about the axle, as often experienced during
braking.
As such, suspensions using air springs as the primary means of support
typically
require a combination of beams and torque rods in order to take the braking
and
cornering forces. Examples of such an arrangement are seen in the Hendrickson
Parasteer HD (trademark) and Primaax (trademark) front suspensions which
employ systems of mechanical linkages to mount air springs beneath the
chassis.
Both of these suspension systems use laterally extending torque rods to
stabilize
the assembly and protect the air springs from lateral loads.
It will be appreciated however that torque rods and the like occupy valuable
space
between and around the frame rails which can conflict with other vehicle
components. This problem is most acute for steerable front axles which are
proximate transmission, engine and/or steering components.
Similarly, it is known to arrange a combination of air springs and leaf
springs so as
to protect the former from lateral loads. Examples of such a combination can
be
found in the U.S. patent mentioned above, as well as in the Kenworth AG130
(trademark) front air suspension which nonetheless includes other lateral
members for providing lateral support. However, it would be advantageous to
remove the need for leaf springs.
Also known in the art are the following patents and published applications
which
also describe vehicle suspensions and the like: US 3,063,732, US 3,233,915, US
3,285,621, US 3,762,487, US 3,902,734, US 4,619,467, US 4,676,523, US
4,966,387, US 5,271,638, US 5,354,091, US 5,615,906, US 5,873,581, US
6,224,074, US 6,276,710, US 6,364,340, US 6,460,872, US 6,857,647, US
2004/0080136, US 2005/0263986, and US 2006/0208464.
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However, there remains a need for a vehicle suspension which makes better use
of the afore-mentioned advantageous features of air springs and is able to
provide
increased ride comfort for a user.
Summary of the Invention:
An object of the present invention is to provide a vehicle suspension which,
by
virtue of its design and components, satisfies some of the above-mentioned
needs
and is thus an improvement over other related devices and/or suspension
systems
known in the prior art.
According to a first aspect of the invention, a suspension system for a
vehicle
chassis is provided which includes a pivoting structure which includes a
vehicle
axle and a pair of trailing arms, a pair of air springs for absorbing shocks
experienced by the vehicle axle and a guiding assembly for preventing lateral
loads from being transferred to the air springs. Each trailing arm is
pivotally
mounted to the vehicle chassis and fixedly mounted to the vehicle axle so as
to
permit an arcuate movement of the vehicle axle with respect to the vehicle
chassis. The pivoting structure has a first lateral surface facing in a first
lateral
direction and a second lateral surface facing in a second lateral direction,
and the
second lateral direction is opposite the first lateral direction. Each air
spring is
fixedly mounted between the vehicle chassis and the vehicle axle along a
respective one of the pair of trailing arms. The guiding assembly includes a
first
guide element mounted beneath the vehicle chassis which extends proximate the
first lateral surface so as to block lateral movement thereof in the first
lateral
direction. The guiding assembly further includes a second guide element
mounted
beneath the vehicle chassis and which extends proximate the second lateral
surface so as to block lateral movement thereof in the second lateral
direction.
Preferably, the first lateral surface extends along either one of the trailing
arms
and the second lateral surface extends along either one of the trailing arms.
More
preferably, each of the pair of trailing arms includes a respective one of a
first
upwardly extending projection and a second upwardly extending projection, the
first lateral surface extending along a first lateral side of the upwardly
extending
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projection and the second lateral surface extending along a second lateral
side of
the second upwardly extending projection.
According to another aspect of the present invention, a tandem suspension
system for a vehicle chassis is provided which includes a first pivoting
structure
including a first vehicle axle and a first pair of trailing arms, a second
pivoting
structure having a second vehicle axle and a second pair of trailing arms, a
first
pair of air springs for absorbing shocks experienced by the first vehicle
axle, a
second pair of air springs for absorbing shocks experienced by the second
vehicle
axle, and a first pivoting structure guiding assembly for preventing lateral
loads
from being transferred to the first pair of air springs. Each of the first
pair of trailing
arms is pivotally mounted to the vehicle chassis and fixedly mounted to the
first
vehicle axle so as to permit an arcuate movement of the first vehicle axle
with
respect to the vehicle chassis. The first pivoting structure has a first
lateral surface
facing in a first lateral direction and a second lateral surface facing in a
second
lateral direction, and the second lateral direction is opposite the first
lateral
direction. Each of the second pair of trailing arms is pivotally mounted to
the
vehicle chassis and fixedly mounted to the second vehicle axle so as to permit
an
arcuate movement of the second vehicle axle with respect to the vehicle
chassis.
Each of the first pair of air springs is mounted between the vehicle chassis
and the
first vehicle axle along a respective one of the first pair of trailing arms.
Each of the
second pair of air springs is mounted between the vehicle chassis and the
second
vehicle axle along a respective one of the second pair of trailing arms. The
first
and second pairs of air springs are pneumatically equalised. The first
pivoting
structure guiding assembly includes a first guide element mounted beneath the
vehicle chassis which extends proximate the first lateral surface so as to
block
lateral movement thereof in the first lateral direction. The first pivoting
structure
guiding assembly includes a second guide element mounted beneath the vehicle
chassis which extends proximate the second lateral surface so as to block
lateral
movement thereof in the second lateral direction.
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Preferably, the vehicle axle is fixedly mounted at a position along each
trailing arm
which is between the pivotal mounting with the vehicle chassis and the fixed
mounting with each air spring.
Preferably, the first lateral surface extends along either one of the trailing
arms
5 and the second lateral surface extends along either one of the trailing
arms.
The expression "lateral", as used herein, should be understood as being
relative to
the frame of reference of the vehicle. The "lateral directions" are therefore
perpendicular to the longitudinal axis of the vehicle and its direction of
travel (when
moving in a straight line), and generally in line with the axle. Moreover, it
will be
understood that physical components, such as surfaces, guides and the like, as
well as the loads experienced by the vehicle suspension, need only have a
component facing or aligned in a lateral direction to be considered "lateral".
As can be appreciated, a vehicle suspension according to the present invention
can advantageously improve the absorption, isolation and dampening of axle
movement during operation of the vehicle. Specifically, a vehicle suspension
according to an embodiment of present invention may enable the incorporation
of
air springs into vehicles where they would otherwise not fit due the reliance
of
conventional air spring suspensions on torque rods and other lateral members
to
provide lateral support.
In addition, it will be appreciated that a vehicle suspension according to the
present invention may be more compact and therefore easier to package beneath
a vehicle chassis. In particular, a vehicle suspension according to the
present
invention may be used without laterally extending torque rods, beams or the
like.
It will also be appreciated that a vehicle suspension according to the present
invention may be easier to install as a retrofit improvement to a conventional
leaf
spring suspension assembly.
The invention and its advantages will be better understood by reading the
following non-restrictive description of a preferred embodiment thereof, made
with
reference to the accompanying drawings.
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Brief Description of the Drawings:
FIG. 1 is a perspective view of a vehicle suspension in accordance with an
embodiment of the present invention.
FIGs. 2 and 3 are side views of the suspension of FIG. 1, the latter including
a
section of the vehicle chassis.
FIG. 4 is an exploded view of the suspension of FIG. 1.
FIG. 5 is a perspective view of a tandem suspension in accordance with another
embodiment of the present invention.
FIG. 6 is a side view of the tandem suspension of FIG. 5, shown attached to
the
vehicle chassis.
FIG. 7 is a top view of a tandem suspension according to yet another
embodiment
of the present invention.
FIGs. 8A and 8B are two perspective views of a preferred embodiment of a
bracket incorporating first and second guide elements.
Detailed Description of Preferred Embodiments of the Invention:
In the following description, the same numerical references refer to similar
elements. The embodiments shown in the figures are preferred, for
exemplification
purposes only.
In addition, although the preferred embodiments of the present invention as
illustrated in the accompanying drawings includes various components, etc.,
and
although the preferred embodiments of the suspension and corresponding parts
of
the present invention as shown consist of certain geometrical configurations
as
explained and illustrated herein, not all of these components and geometries
are
essential to the invention and thus should not be taken in their restrictive
sense,
i.e. these components and geometries should not be taken as to limit the scope
of
the present invention. It is to be understood, as also apparent to a person
skilled in
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the art, that other suitable components and cooperations therebetween, as well
as
other suitable geometrical configurations may be used for the suspension
according to the present invention, as will be briefly explained herein and as
can
be easily inferred herefrom by a person skilled in the art, without departing
from
the scope of the invention.
It will be appreciated that positional descriptions such as "front", "rear"
and the like
should, unless otherwise indicated, be taken in the context of the figures and
should not be considered limiting.
With reference to FIGs. 1 to 3, a suspension system 10 for a vehicle chassis
18
according to one embodiment of the invention is shown. The suspension system
includes a pivoting structure formed by a vehicle axle 12 and a pair of
trailing arms
16. The axle 12 includes a spindle 14 at either extremity to which wheels (not
shown) are mounted, as is known in the art. The axle 12 of the illustrated
embodiment is a steered axle having a steering linkage 20, although it will be
appreciated that other types of axles, such as non-steered axles or
drive/steer
axles, may similarly be mounted to the chassis 18 within a suspension system
10
in accordance with the present invention.
The trailing arms 16 are elongate members which are pivotally mounted to the
chassis 18 at one end so as to extend rearwards therefrom. Each trailing arm
16 is
further fixedly mounted to the vehicle axle 12, in this manner, an arcuate
movement of the vehicle axle 12 with respect to the chassis 18 is permitted.
In
fact, in the illustrated embodiment the entire pivoting structure, formed by
the axle
12 and the trailing arms 16 together, follows an arcuate movement 30 about an
axis 32 below the chassis 18.
As will be appreciated, the pivotal mounting of the trailing arms 16 to the
chassis
18 can be embodied in a number of different ways, including by providing an
eye
24 at the extremity of each leaf spring 16, which is connected to a bracket 28
by a
pin 26. Preferably, the eyes 24 are sized and shaped like the eyes commonly
found at the extremities of conventional leaf springs. As such, when
installing the
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suspension 10 on an existing vehicle having a conventional leaf spring
suspension, the trailing arms 16 can be installed in the original brackets 28.
Preferably, each trailing arm 16 is unitary in construction and extends
between the
chassis 18 and the axle 12 as a solid, elongate member rather than a multi-
piece
construction having two or more articulating sections such as 4-bar mechanism
or
the like. However, it will be appreciated that a trailing arm 16 constructed
from a
plurality of rigidly connected pieces would provide the same arcuate movement
30
as the illustrated embodiment and should therefore be understood to constitute
a
preferred "unitary" construction.
The suspension system 10 further includes a pair of air springs 34, each one
associated with one of the trailing arms 16. Each air spring 34 is disposed
between the vehicle axle 12 and the chassis 18 so as to prevent or at least
minimise shocks passed between the two. It will be appreciated however that
this
does not mean that the air springs 34 be attached directly to the axle 12,
rather the
air springs 34 can be attached to any suitable component which pivots with the
axle 12 beneath, the chassis 18. Preferably, each air spring 34 is positioned
along
a respective one of the trailing arms 16. Air springs typically have a
substantially
cylindrical form with flat top and bottom faces. The hollow, resilient bodies
of the
air springs 34 are operable to expand and contract vertically so as to, inter
alia,
absorb vertical shocks experienced by the axle 12, as will be appreciated by
one
of ordinary skill in the art and will not be discussed in further detail
herein.
The air springs 34 are connected to a pneumatic system 36, shown schematically
in FIG. 2, which includes a tank for supplying pressurized air to the springs
34, as
well as means for controlling the air pressure therein. The use and control of
these
elements is known in the art and will not be discussed further herein.
The bottom face 38 of each air spring 34 is fixed to a respective trailing arm
16
and its top face 40 is fixed to the chassis 18. Preferably, each trailing arm
16
comprises a beam portion 42 having the eye 24 at one end, and an air spring
seat
44 which is attached at the opposite end of the beam portion 42 and which
receives the bottom face 38.
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With additional reference to FIG. 4, the spring seats 42 are preferably
constructed
so as to lower of the air springs 34 with respect to the remainder of the
trailing
arms 18. Each spring seat 44 comprises a spacing block 46 which is connected
to
the underside of the beam portion 42 and extends downwards therefrom, and a
support plate 48 attached to the underside of the spacing block 46 which
provides
a receiving area 50 sized and shaped to receive the bottom face 38. If
necessary,
a spacing plate 52 may be positioned between the bottom face 38 and the
support
plate 48 in accordance with the dimensions of the specific air spring 34. As
will be
appreciated by one skilled in the art, the size of the spacing plate 52 can
affect the
ride height and travel of the suspension 10, while the size of the block 46
can
affect the caster angle of the axle 12. As seen in FIG. 3, the top face 40 of
each air
spring fixed to the chassis via a respective bracket 64.
In the embodiment illustrated, and as seen most readily in the side views of
FIGs.
2 and 3, the axle 12 is attached to the trailing arms 16 at a position between
the air
springs 34 and the eyes 24. In this arrangement the distance between the
pivoting
axis 32 and the air springs 34 is greater than the distance between the
pivoting
axis 32 and the axle 12. Accordingly, the air springs 34 (or more precisely
their
bottom faces 38) will experience a greater displacement than the axle 12 as
the
latter moves with respect to the chassis 18. In contrast to a conventional
suspension system which positions its air springs directly over the axle, this
use of
mechanical advantage, or leverage, advantageously increases the degree to
which the air springs 34 can absorb shocks experienced by the axle 12 and
allows
for the use of smaller air springs. In addition, this arrangement can allow
for a
more convenient packaging of the components of the suspension system 10. It
will
be appreciated however that the precise positions and distances of these
elements may be varied in accordance with the specific geometry and/or
arrangement of the suspension system 10.
In the illustrated non-limitative embodiment of FIGs. 1 to 4, the axle 12 and
trailing
arms 16 are fixedly attached by a pair of U-bolts 54 which extend over the
trailing
arms 16 and through a corresponding set of bolt holes 56 within a flattened
area
58 formed along the axle 12. As is known in the art, nuts 60 can then be used
to
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retain the threaded extremities of the U-bolts 54, which extend beneath the
axle
12. Preferably, the beam portion 42, the spacing block 46 and a portion of the
support plate 48 opposite the receiving area 50 are all aligned above the axle
12
and are bound thereto by the U-bolts 54. An axle stopper 62 is also preferably
5 attached above the axle 12, and retained by the U-bolts 54, so as to limit
the
upward range of motion of the axle 12 and limit the maximum deflection of the
air
springs 34. As seen in FIG. 3, when the axle stopper 62 reaches the underside
of
the chassis 18, the axle 12 cannot rise any further.
The pivoting structure 22 further includes at least one set of first and
second
10 lateral surfaces 70 and 72 which face in opposed first and second lateral
directions
74 and 76. As will be discussed in further detail below, the suspension system
10
further includes a guiding assembly 78 which interact with the first and
second
lateral surfaces 70 and 72 so as to block lateral movement of the axle 12 with
respect to the chassis 18 and prevent lateral loads imparted to the axle 12
from
being transferred to the air springs 34 in a potentially damaging manner.
Preferably, the lateral surfaces 70 and 72 are formed by upwardly extending
projections 80 which are present on one or both trailing arms 16. As seen most
clearly in FIG. 4, the illustrated embodiment of the suspension system 10
includes
two projections 80 which extend upwards from respective ones of the beam
portions 42. These projections 80 have a rectangular hollow body 82 which
forms
the first and second lateral surfaces 70 and 72 on either lateral side
thereof.
Specifically, the first lateral surface 70 is formed along the left side of
the body 82
which faces in the first lateral direction 74, while the second lateral
surface 72 is
formed along the right side of the body 82 which faces in the second lateral
direction 76. The upwardly extending projection 80 further includes a base
portion
84 which extends along the beam portion 42 of the respective trailing arm 16
so as
to be sandwiched by the U-bolts 54 along with the axle stopper 62, the spacing
block 46 and the support plate 48.
As mentioned above, the suspension system 10 further includes the pivoting
structure guiding assembly 78, referred hereinafter as the "guiding assembly"
for
simplicity. The guiding assembly 78 includes a pair of guide elements 86a and
86b
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11
which are fixed to the chassis 18 and extend alongside respective ones of the
first
and second lateral surfaces 70 and 72. As seen in FIG. 3 which shows only the
first guide element 86a, the bracket 64 which attaches the top face 40 of the
air
spring 34 to the chassis 18 can be combined with the downwardly extending
guide
element 86a which is positioned next to the first (left) lateral side 70 of
the
partially-hidden projection 80. It will be appreciated however that the guide
element 86a need not be combined with the bracket 64 in this manner. Indeed,
the
projection 80 could be placed elsewhere along the trailing arm 16, or the
lateral
surfaces 70 and 72 could be placed elsewhere along the pivoting structure 22
and
the guiding assembly 78 positioned accordingly.
With reference to FIGs. 8A and 8B, a preferred embodiment of a bracket 64
incorporating a first guide element 86a and a second guide element 86b is
shown.
The bracket 64 includes a vertical panel 66 and a horizontal panel 68 which
are
attached (alongside and underneath, respectively) to the chassis 18 as seen in
FIGs. 3 and 6. Below the panels 66 and 68, the bracket 64 forms another
receiving
area 88 which is sized and shaped to receive the top face 40 of the respective
air
spring 34.
When the lateral surfaces 70 and 72 of the pivoting structure 22 are located
near
the air springs 34, it can be convenient to combine the air springs bracket 64
and
the guiding assembly 78 in a single structure. As shown in the illustrated
embodiment, the first and second guide elements 86a and 86b are elongate
plates
which extend below the horizontal panel 68, parallel to the vertical panel 66.
It will
be appreciated however that various other embodiments of both the bracket
guiding assembly are well within the scope of the present invention.
The brackets 64 and guiding assembly 78 are preferably formed from sections of
sheet metal, which can be cut, bent, welded or otherwise worked so as to form
the
above-described structure. As such, the brackets 64 and guiding assembly 78
can
be provided with reinforcing members 90 which strengthen and solidify the
structure. It will be apparent, however, to one of ordinary skill in the art
that various
other materials and construction techniques could similarly be used in
accordance
with other embodiments of the present invention.
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12
In use, the guide elements 86a and 86b are positioned sufficiently close to
their
respective lateral sides 70 and 72 and built sufficiently robustly to
counteract any
lateral movement experienced by the pivoting structure 22 which might be
damaging to the air springs 34. The guide elements 86a and 86b should
preferably
not be so close to the lateral sides 70 and 72 that they unduly impede or
otherwise
negatively effect the arcuate movement 30 of the pivoting structure 22. It
will be
appreciated however that the air springs 34 may tolerate a certain amount of
lateral play. It will also be appreciated that the guide elements 86a and 86b
can be
provided with inserts 92 such as the shims shown in FIGs. 8A and 8B, which can
be installed between the lateral surfaces 70 and 72 and the guide elements 86a
and 86b. In the illustrated embodiment, these shims 92 are fixed to the guide
elements 86a and 86b although they could also be fixed along the first and
second
lateral surfaces 70 and 72. Such inserts 92 could be bushings selected from a
material which reduces friction between each lateral surface 70 or 72 and the
adjacent guide elements 86a and 86b and also serve as wear parts.
When assembled, the upwardly extending projection 80 will fit between the
guide
elements 86a and 86b such that the first lateral surface 70 faces the first
guide
element 86a and the second lateral surface 72 faces the second guide element
86b. The guide element 86a visible in FIG. 3 is positioned across from the
first
lateral surface 70, which is to say leftwards in the frame of reference of the
vehicle. Accordingly, the presence of the first guide element 86a therefore
prevents displacement of the projection 80, and hence the pivoting structure
22 of
which it is rigidly a part, in the first lateral direction. Similarly, the
second guide
element 86b will block movement of the upwardly extending projection 80, and
hence the whole pivoting structure 22, in the second lateral direction 86.
It will be appreciated therefore that various combinations of lateral surfaces
70 and
72 and guide elements 86a and 86b can be used according to the specific
constraints of the suspension system 10 and/or the vehicle. The first and
second
lateral surfaces 70 and 72 can both be provided along either one of the left
side or
right side trailing arms 16, in which case the guiding assembly 78 is mounted
on
just one side of the suspension system 10. Alternatively, the first lateral
surface 70
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13
and the second lateral surface 72 can be provided .on separate trailing arms
16.
When only one of each projection 80's lateral surfaces 70 and 72 is provided,
or
when only one is utilised, the guide elements 86a and 86b will be provided
either
outside the pair of trailing arms 16, that is to say to the left of the left
trailing arm
16 and to the right of the right trailing arm 16, or between the two trailing
arms 16,
that is to say to the right of the left trailing arm 16 and to the left of the
right trailing
arm 16.
While only two oppositely facing lateral surfaces 70 and 72 are required, all
four
are preferably utilized by providing pairs of guide elements 86a and 86b on
both
sides of each projection 80. In the case of the illustrated embodiment, that
means
each of the two brackets 64 would include first and second downwardly
extending
guide elements 86a and 86b so as to doubly block lateral movement. In this
doubly blocking embodiment, the upwardly extending projections 80 can be
considered male members which fit between the female pairs of first and second
downwardly extending guide elements 86a and 86b.
Preferably and as illustrated, both the lateral surfaces 70 and 72 and their
respective guide elements 86a and 86b are flat and parallel to one another,
facing
only in one of the two lateral directions 74 or 76. However, as noted above,
the
lateral surfaces 70 and 72 need only have a component or portion thereof which
is
facing one of the lateral directions 74 and 76 in order to engage the guide
elements 86a and 86b positioned therebeside when the axle is pushed laterally.
As such, the lateral surfaces 70 and 72 may be angled with respect to the
lateral
directions 74 and 76 and/or may be curved. Similarly, the guide elements 86a
and
86b need not be flat or perfectly aligned with the surfaces 70 and 72. Rather,
they
must merely be positioned to block undesired lateral movement of the pivoting
structure 22.
The suspension system 10 can be used to support a single axle 12, as shown in
FIGs. 1 to 4, or in combination as part of a tandem suspension. With reference
now to FIGs. 5, 6 and 7, a tandem suspension 100 is shown which includes two
single axle suspensions 102 and 104 that are equalized pneumatically by a
pneumatic system 106. The first single axle suspension 102, here at the front
of
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the tandem suspension 100, includes a first pivoting structure 108 which is
made
up of a first axle 110 and a first pair of trailing arms 112, as per the
previously
described suspension system 10. The first suspension 102 further includes a
first
pair of air springs 114.
The front suspension system 102 can be coupled to various types of air spring
suspensions in order to form a tandem suspension 100. Preferably however, the
rear single axle suspension 104 similarly comprises a rear pivoting structure
116
which is made up of a rear axle 118 and a pair of rear trailing arms 120, as
well as
a pair of rear air springs 122, as per the previously described suspension
system
10. The front and rear air springs 122 are pneumatically balanced by the
pneumatic system 106 and this balancing enables loads taken by one of the
front
air springs 114 to be shared with the corresponding rear air spring 122. It is
less
common, although certainly possible, to balance loads between the left and
right
side air springs 114 or 122 since this may affect the operation of the tandem
suspension 100 during braking and cornering.
This rear pivoting structure 116 will comprise third and fourth lateral
surfaces 126
and 128 which are equivalent to the first and second lateral surfaces 126 and
128
referred to above. Similarly, the third and fourth lateral 140 and 142 face in
the first
and second lateral directions 74 and 76, respectively.
It is not uncommon to upgrade a vehicle by replacing an existing single axle
leaf
spring suspension with a tandem suspension, such as the tandem suspension
100, in order to improve its ride comfort. As mentioned above, the present
invention can be advantageously applied to such a retrofit since the front
trailing
arm 112 can be pivotally attached to the chassis 18 via the original leaf
spring
bracket 28 (FIG. 6).
As described above in relation to the illustrated embodiment of the suspension
system 10, the tandem suspension 100 is preferably provided with lateral
surfaces
126 and 128 along portions of each of the front and rear trailing arms 112 and
120.
The tandem suspension 100 further includes a front guiding assembly 130 having
first and second guide elements 136a and 136b which interact with the first
and
CA 02720356 2010-11-05
second surfaces 126 and 128, as well as a rear guiding assembly 132 having
third
and fourth guide elements 144 and 146 which interact with the third and forth
lateral surfaces 140 and 142.
Alternatively, and as shown schematically in FIG. 7, the first and second
lateral
5 surfaces 126 and 128 could be provided along one of the axles 114 or 118
instead
of one or both of the trailing arms. In this alternate embodiment, the axle
110 is
provided with an upwardly extending projection 134 which forms the first and
second lateral surfaces 126 and 128, and the corresponding first and second
guide elements 136a and 136b are mounted proximate thereto. It will be
10 appreciated that providing the lateral surfaces 126 and 128 on this part of
the
pivoting structures 108 and/or 116 will similarly prevent lateral loads from
being
transmitted to the air springs 114 and/or 122.
Advantageously, the above suspension systems 10 and 100 could be applied to
tridem or other multi-axle systems, both steered and un-steered, by further
linking
15 and balancing the air springs. As such, the need for a mechanical balancing
system such as an equaliser bar and the like is avoided.
As being now better appreciated, the present invention is an improvement and
presents several advantages over other related devices and/or methods known in
the prior art. Indeed, embodiments of the present invention are particularly
advantageous in that they avoid the need for laterally extending torque rods
and
the like, thereby easing packaging of the suspension below the chassis. In
addition, it will be appreciated that a suspension in accordance with the
present
invention can be conveniently installed in place of a conventional single axle
leaf
spring suspension system as part of a retrofit process.
Of course, numerous modifications could be made to the above-described
embodiments without departing from the scope of the invention, as apparent to
a
person skilled in the art. While a specific embodiment of the present
invention has
been described and illustrated, it will be apparent to those skilled in the
art that
numerous modifications and variations can be made without departing from the
scope of the invention as defined in the appended claims.
