Note: Descriptions are shown in the official language in which they were submitted.
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TRAILING ARM SUSPENSION
$ACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a trailing arm structure in a trailing arm
suspension for heavy duty vehicles.
I?escription of Related Art
Heavy-duty vehicle suspension systems are typically characterized by
high-strength components, which are relatively heavy. It is desirable to
reduce
the weight of the suspensions without loss of strength in order to more
efficiently carry loads and lower fuel costs.
Trailing ann suspensions are well known. Such suspensions typically
comprise a frame bracket, also known as a hanger bracket, that is secured to
the frame on each side of the vehicle and a trailing arm, pivotally mounted at
one end to each frame bracket and extending rearwardly therefrom. An air
spring is mounted between the other end of each trailing arm and the vehicle
frame. The trailing arms support a vehicle axle at rigid or semirigid
connections with the trailing arms.
Raidel, in U.S. Pat. No. 4,465,298, issued August 14, 1984, discloses a
trailing arm suspension having a torque beam with two horizontally displaced
members connected by a vertical member. The horizontal and vertical
members are extruded hollow rectangular beams having varying dimensions in
the various members. Although the beam appears to function properly, the
extruded construction is relatively expensive and unnecessarily adds to the
cost
of the suspension.
Bird, in U.S. Pat. No. 3,547,215, issued Dec. 16, 1970, discloses a
trailing arm suspension with a box-beam trailing arm comprising four plates, a
top plate, bottom plate, and opposing side plates, welded together to form the
trailing arm. Bird requires at least four longitudinal welds to assemble the
beam portion of the trailing arm.
Wallace et al., in U.S. Patent No. 4,858,949 issued August 22, 1989,
discloses a trailing arm suspension with a trailing arm having an I-beamlike
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construction. The I-beamlike construction requires that the trailing arm be
cast or forged rather than fabricated from separate pieces.
SUMMARY OF INVENTION
The invention lies in a fabricated beam for use in a trailing arm
suspension that is relatively simple in construction and inexpensive to
assemble. The basic beam is formed of three pieces connected at two joints.
A shock absorber bracket is integrally formed with the basic beam. A casting
fixed in a preformed seat in the basic beam facilitates an axle connection
with
the beam.
In one aspect, the beam comprises a longitudinal rib having top and
bottom edges. First and second side channel plates are disposed on opposite
sides of the longitudinal rib. Each of the first and second side channel
plates
has top and bottom lateral walls and a bight portion. The top and bottom
lateral walls of the first and second side channel plates have side channel
plate
edges. The longitudinal rib and the first and second side channel plates are
connected by a top weld securing the first and second top side channel plate
edges to the longitudinal rib top edge and a bottom weld securing the first
and
second bottom side channel plate edges to the longitudinal rib bottom edge.
Preferably, the top weld and the bottom welds are longitudinal. The
first and second top side channel plate edges and the longitudinal rib top
edge
define a notch in which the top weld is disposed. Similarly the first and
second bottom side channel plate edges and the longitudinal rib bottom edge
can also define a notch in which the bottom weld is disposed. Generally, the
longitudinal rib and first and second side channel plates are stamped from
steel.
The beam has means for mounting an axle. Preferably, the axle
mounting means comprises a seat in the beam in which is disposed a cast ,
member having an aperture for mounting the axle. The beam also has a seat
at one end of the beam in which is mounted a collar for pivotally mounting
the beam to the vehicle frame. Generally, the longitudinal rib and the first
and second channel plates are curved to form a curved beam. The other end
of the beam mounts a shaft assembly to enable a transverse beam to connect
trailing arms on opposite sides of the vehicle.
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The longitudinal rib can have a portion with an aperture that extends
beyond the first and second side channel plate edges to form a shock bracket.
' In another aspect, the invention is directed to a trailing arm adapted
for use in a trailing arm suspension wherein the trailing arm comprises first
and second ends with the first end having means to pivotally mount the
trailing arm to a vehicle frame and axle mounting means intermediate the first
and second ends. The axle mounting means comprises a seat in the trailing
arm and a cast member having an aperture complementary in shape to the
shape of the seat and welded to the seat. Preferably, the seat is
substantially
U-shaped and the aperture is substantially circular. The cast member has a
locating rib for positioning the cast member with respect to the trailing arm.
In yet another aspect of the invention, a trailing arm suspension
comprises a trailing arm having first and second ends, the first end being
pivotally mounted to the vehicle frame and the second end being mounted to
the vehicle frame by a force dampening means for dampening forces imparted
to the trailing arm suspension. The trailing arm comprises a longitudinal rib
having top and bottom edges. First and second side channel plates having top
and bottom lateral walls and a bight portion are welded to the longitudinal
rib. The lateral walls of the first and second channel plates have edges. A
top weld secures the first and second top lateral wall edges to the top
longitudinal rib edge and a bottom weld secures the first and second bottom
lateral wall edges to the bottom longitudinal rib edge.
BRIEF DESCRIPTION OF THE DRAWIN
The invention will now be described with reference to the drawings
wherein:
FIG. 1 is a plan view of a trailing arm suspension incorporating the
trailing arm according to the invention;
FIG. 2 is an exploded view of the trailing arm of FIG 1;
FIG. 3 is an elevational view of the trailing arm of FTG. 1 with parts
~0 cut away for clarity;
FIG. 4 is a top view of the trailing arm of FIG. 3;
FIG. 5 is a sectional view taken along lines 5-5 of FIG. 3;
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FIG. 6 is a sectional view taken along lines 6-6 of FIG. 3; and
FIG. 7 is a sectional view taken along lines 7-7 of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a vehicle having a trailing arm suspension 10
incorporating a trailing arm 12 according to the invention. A portion of a
vehicle frame 14 is shown, with the front of the vehicle to the left in FIG.
1.
The suspension 10 mounts the frame 14 to ground engaging wheels 26 and
tires 28 (only one of which is shown in FIG. 1). It will be understood that a
complete suspension 10 comprises a pair of trailing arms 12, one each
mounted to opposite sides of the vehicle. For clarity, however, only one side
of the vehicle is illustrated in FIG. 1.
The trailing arm 12 Is pivotally mounted at one end 17 by a bushed
connection 18 to a frame bracket assembly 16, which is rigidly fixed to the
vehicle frame 14. The bushed connection 18 is commonly known in the art.
The trailing arm 12 mounts an air spring assembly 22, either on the free end
23 of the trailing arm or an extension thereof. The upper portion of the air
spring assembly 22 is secured to the frame 14 to enable the air spring to
cushion the normal upward and downward movement of the frame when the
vehicle is in motion. A shock absorber 20 extending between the trailing arm
12 and the vehicle frame 14 dampens the upward and downward motion. An
axle 24 carrying the ground engaging wheels 26 and tires 28, is securely
mounted to the trailing arm 12 intermediate the ends 17, 23.
Referring to FIGS. 1, 2 and 3, the trailing arm 12 is generally J-shaped
in elevational profile, adapted to initially extend downwardly from the
vehicle
frame 14 and then extend rearwardly thereof. The J-shape of the trailing arm
12 provides one end of the trailing arm 12 for mounting to the vehicle frame
14 with a relatively short frame bracket 16 while maintaining a separation
between the frame 14 and the free end 23 of the traMing arm 12 so that
suspension members such as shock absorber 20 and air spring 22 can be
mounted between the other end of the trailing arm 12 and the frame 14. One
end 17 of the trailing arm 12 has a mounting collar 36 for receiving a bushing
and pin to form the bushed connection 18 to mount the trailing arm 12 to the
frame bracket assembly 16. The free end 23 of the trailing arm 12 mounts an
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end shaft 48, which is adapted to receive a complementary collar in a bushed
connection for a transverse beam extending between the trailing arms on
opposite sides of the vehicle in a manner well known in the art- The
transverse beam resists torsional forces acting on the trailing arms, thereby
providing some resistance to roll and sway. The transverse beam sometimes
supports the air springs 22. A cast member 40 for mounting a bushed
connection 98 that mounts axle 24 to the trailing arm 12 is mounted between
the ends 17 and 23 of the trailing arm.
Referring specifically to FIGS. 2 - 4 and generally to FIG. 5, the
trailing arm 12 comprises a central rib 32 that serves as the spine of the
trailing arm 12. The central rib has a top edge 33 and a bottom edge 35 as
best seen in FIGS. 2 and 5. The central rib 32 has a semicircular recess 34 in
which the mounting collar 36 is received. An arcuate recess 38 located
between the ends of the central rib receives the cast member 40. A shock
bracket or extension 42 of the central rib 32 has a shock absorber opening 44
for mounting shock absorber 20. The other end of the central rib 32 adjacent
the air spring 22 has a rectangular recess 46 for mounting the end shaft 48.
The complexity of assembling the trailing arm suspension is reduced by
integrating the shock absorber bracket 42 with the central rib 32 rather than
attaching a separate shock absorber bracket after assembly of the trailing arm
as done in prior trailing arm suspensions.
The trailing arm 12 also comprises side plates 52 and 54 which are
channel-shaped, preferably being U-shaped in cross section. Other cross
sections, such as a C-shape or a V-shape, for example, are suitable. The side
plates 52 and 54 are welded to the central rib 32 by upper weld 66 and lower
weld 68 to form a box beam with a central rib or spine. Although the welds
66 and 68 are illustrated as extending the longitudinal length of the central
web 32, the welds 66 and 68 can be spot welded. The side plates 52 and 54
are mirror images of each other. Therefore, only one of the side plates will
be described in detail. Side plate 52 has a top lateral wall 59 and a bottom
lateral wall 60 connected by a bight portion 61. The top lateral wall 59 and
bottom lateral wall 60 have a top edge 84 and a bottom edge 86, respectively.
Side plate 52 has a semicircular recess 56, which is congruent in shape to the
semicircular recess 34 of the central rib 32 for mounting the mounting collar
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36. The semicircular recesses 34 and 56 of the central rib 32 and side plates
52, 54 form a first seat 55 for mounting the mounting collar 36. The mounting
collar 36 is also welded to the central rib 32 and side plates 52 and 54 by
welds 69 and 70.
Preferably, at least one shock absorber mount plate 110 with
aperture 112 is welded to one of the side plates 52 and 54. The shock
absorber mount plate 110 cooperates with the shock absorber bracket 42 to
form a clevis with which to mount a shock absorber. The side plate 52 or 54
to which the shock mount plate 110 is mounted depends on which side of the
vehicle the trailing arm is disposed. Alternatively, shock mount plates 110
having apertures 112 can be mounted, preferably by welding, to both side
plates 52 and 54 so that the trailing arm 12 can be used as a left or right
hand
trailing arm 12 (FIG. 7). In this manner, the trailing arm 12 is a universal
trailing arm.
Referring now to FIGS. 2, 3 and 6, the side plate 52 also has an
arcuate recess 58 that is congruent in shape to arcuate recess 38 of the
central
rib 32 for mounting the cast member 40 although not as deep as the arcuate
recess 38. The arcuate recesses 38 and 58 of the central rib 32 and side
plates
52, 54 form a second seat 57 for mounting the cast member 40. Preferably,
the central rib 32 and the side plates 52, 54 are formed of stamped steel
plate.
The cast member 40 is generally tubular having a central aperture 76,
and is preferably made from steel. The casting has reduced diameter portions
78 and 80 that define an alignment rib 82. The alignment rib 82 is disposed
between the side plates 52 and 54 to align the cast member 40 within the
trailing arm 12 and second seat 57. The cast member 40 is disposed within
the arcuate recesses 38 and 58 with the reduced diameter portions 78, 80
resting in the recess 58 and the rib 82 resting in the recess 38. The cast
member 40 is welded to the central rib 32 by a weld (not shown) and side
plates 52 and 54 by welds 72 and 74. A bushed connection 98 is mounted
within the aperture 76 of the cast member 40. The bushed connection 98 is ,
common in the art.
Referring to FIG. 2, the axle 24 is mounted to the trailing arm 12 by
axle bracket 100. Axle bracket 100 has opposing plates 102 that have an
aperture 104 at one end to mount the plates 102 to the bushed connection 98.
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The other end of each plate has a conformed surface 106 which supports a
seat 108 welded thereto. The axle 24 is mounted to the seat 108, preferably
by welding.
Referring to PIGS. 2 and 6, an end plate 62 having an opening 64 for
receiving the end shaft 48 is welded to the central rib 32 and side plates 52
and 54 by weld 65 to complete the trailing arm 12. It will be apparent that
only three welds are needed to assemble the basic structure of the trailing
arm
12, a significant reduction from the number required in prior fabricated
trailing arms.
To assemble the trailing arm 12 according to the invention, the
mounting collar 36, cast member 40, and end shaft 48 are mounted to the
central web. The mounting collar 36 is placed within the semicircular recess
34 and preferably welded thereto. The cast member 40 is placed within the
arcuate recess 38 and welded thereto. In a similar manner, the end shaft 48 is
positioned within the rectangular recess 46 and welded to the central rib 32.
After the mounting collar 36, cast member 40, and end shaft 48 are
mounted to the central rib 32, the side plates 52 and 54 are mounted to the
central rib 32 by welds 66 and 68. Preferably, the plates 52, 54 are abutted
against opposite sides of the central rib 32, but the central rib 32 is
sufr'tciently
shorter than the side plates 52, 54 so that a top notch 90 and a bottom notch
92 are formed by the top edges 33, 84 and bottom edges 35, 86 respectively.
The welds 66 and 68 are laid in the top notch 90 and bottom notch 92,
respectively. The side plates 52, 54 are then welded to the mounting collar 36
and cast member 40 by welds 69, 70 and 72, 74, respectively.
The end plate 62 is then pressed onto the end shaft 48 and welded to
the central rib 32 and side plates 52, 54 by welds 65. Alternatively, the end
plate 62 can be pressed onto the end shaft 48 prior to the welding of the end
shaft 48 to the central rib 32.
The present invention greatly simplifies the assembly of the trailing arm
12. Other benefits include a lack of any required machining prior to or after
assembly to form an aperture for receiving the axle 24 of the trailing arm
suspension. Nor does a special shock absorber mounting bracket need be
added to the trailing arm 12 after assembly because the center rib 32 has a
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shock absorber bracket 42 with opening 44 integrally formed with the central
rib 32 for mounting shock absorber 20.
While particular embodiments of the invention have been shown, it will
be understood, of course, that the invention is not limited thereto since
modifications may be made by those skilled in the art, particularly in light
of
the foregoing teachings. Reasonable variation and modification are possible
within the scope of the foregoing disclosure of the invention without
departing
from the spirit of the invention.
