Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-09-19
2002-03-19
Dickson, Paul N. (Department: 3618)
Land vehicles
Wheeled
Running gear
Reexamination Certificate
active
06357768
ABSTRACT:
TECHNICAL FIELD
The present invention relates to solid axle suspensions for motor vehicles, more particularly to a straight line linkage mechanism guidably positioned between the frame and a solid axle of a motor vehicle.
BACKGROUND OF THE INVENTION
The rear axles of vehicles can generally be classified as independent, twist or solid. With a solid axle the two rear-wheels of a vehicle are connected together with some form of a rigid beam, bar or tube so that when one of the wheels encounters an irregularity in the road surface the other wheel is also affected. Most commonly, a solid axle is used at the rear of a rear-wheel drive or four wheel drive motor vehicle, particularly light trucks, the solid axle being “live axle”, in the sense that the attached left and right wheels are driven through the axle via a connected drive shaft from the vehicle's engine.
As exemplified at
FIG. 1
, a solid axle
10
is mounted to a suspension system which allows the axle to travel vertically as the wheels track over rises and dips on a road (or off-road) surface. In order for the axle to accommodate vertical travel relative to the frame
12
(shown cut-away for clarity), the axle is biasably mounted relative to the frame, as for example including a pair of leaf or coil springs
14
and a pair of shock absorbers
16
. In order to provide proper tracking of the axle as it undergoes vertical movement relative to the frame, it is known in the art to employ a track bar linkage
18
. A track bar is a rigid metal beam having a pivotal frame attachment
20
at one end, and a pivotal axle attachment
22
at the other end. For a further detailed description of a suspension system associated with a track bar linkage, see U.S. Pat. No. 5,884,925 to Wong.
A deficiency of the track bar is that as the axle moves vertically, the track bar requires that the axle attachment arc pivotally in relation to the frame attachment. One known solution is to replace a track bar linkage with a “Scott-Russell” linkage mechanism.
FIG. 2
shows such a Scott-Russell linkage mechanism
50
associated with a suspension system which is structurally and functionally substantially the same as that described above. The Scott-Russell linkage mechanism
50
includes a rigid beam
52
, a connector rod
54
and a link
56
. The link
56
is pivotally connected to the axle
58
and to a first end
60
of the beam. A second end
62
of the beam is pivotally connected to the frame
64
(shown cut-away for clarity). The connector rod
54
is pivotally connected between a mid-point location of the beam and a mid-region location of the axle.
FIG. 3
diagrammatically depicts the above described Scott-Russell linkage mechanism
50
. The theory of ideal operation of the Scott-Russell linkage mechanism is as follows: since the connector rod
54
is half as long as the beam
52
and since the connector rod is connected to the mid-point of the beam, as the axle
58
moves vertically relative to the frame
64
, the first end
60
of the beam
52
would move horizontally, allowing for vertical movement of the axle. However, in practice, the first end
62
is not able to move truly horizontally because of the associated pivoting of the link
56
. Accordingly, a Scott-Russell linkage mechanism has a deficiency in that the link
56
forces the first end
60
of the beam to move in a vertical arc
64
rather than truly horizontally.
What remains needed in the art is a linkage which overcomes the aforesaid deficiency of a Scott-Russell linkage mechanism.
SUMMARY OF THE INVENTION
The present invention is a solid axle guidance linkage mechanism having a straight line movement which does not suffer from the movement deficiencies associated with either a track bar linkage or a Scott-Russell linkage mechanism.
The straight line linkage mechanism according to the present invention, (which may be referred to alternatively as either a “Chan-Cameron mechanism” or a “Chan-Cameron linkage mechanism”) includes a main bar, a tie rod and a shackle. The shackle is preferably configured as an “A-arm”, having its legs pivotally connected to a solid axle. The apex of the shackle is pivotally connected to a first end of the main bar. The opposite second end of the main bar is pivotally connected to the frame. The tie rod is pivotally connected at one end to a mid-range location of the axle and, at its opposite end, pivotally to a mid-point location of the main bar. The connection locations of the main bar are spaced apart twice as far as the connection locations of the tie rod.
In operation, as the axle moves vertically relative to the frame in response to the wheels encountering irregular terrain, the first end of the main bar will tend to move horizontally. The shackle is mounted to the axle so that the apex thereof is horizontally movable. Accordingly, the axle is able to move vertically relative to the frame without a vertical arc component.
Accordingly, it is an object of the present invention to provide a straight line linkage mechanism for a solid axle.
This and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification.
REFERENCES:
patent: 2669315 (1954-02-01), Butterfield
patent: 3220502 (1965-11-01), Muller
patent: 4545266 (1985-10-01), Brems
patent: 5439091 (1995-08-01), Mason
patent: 5445404 (1995-08-01), Shida et al.
patent: 5884925 (1999-03-01), Wong
patent: 6179328 (2001-01-01), Kawagoe et al.
Cameron David S.
Chan Stephen K.
Dickson Paul N.
Fleming Faye M.
General Motors Corporation
Hargitt Laura C.
Sedlar Jeffrey A.
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