Swing arm

Details Swing arm Swing arm

2003-01-22

2004-09-21

Morris, Lesley D. (Department: 3611)

Motor vehicles

Including one or more ski-like or runner members

C180S190000, C280S124128

Reexamination Certificate

active

06793030

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns the construction of a swing arm to which a ski of a snowmobile is attached. In particular, this invention encompasses a swing arm construction for the front suspension of a snowmobile that facilitates the passage of snow and other elements underneath the swing arm.
2. Description of Related Prior Art
FIG. 6
illustrates a conventional snowmobile
10
, which is manufactured by Bombardier Inc. of Montreal, Quebec, Canada. While only the left side of the snowmobile
10
is illustrated, those skilled in the art would readily appreciate that the right side is essentially a mirror image thereof.
The snowmobile
10
is constructed with a frame
12
powered by a motor
14
. The motor
14
is preferably an internal combustion engine, which may be one of either the two-stroke or four-stroke variety. Handlebars
16
are disposed above and to the rear of the motor
14
. The handlebars
16
operatively connect to two skis
18
,
20
disposed at the front of the snowmobile
10
. When turned by the handlebars
16
, the skis
18
,
20
turn the snowmobile
10
in the desired direction.
The skis
18
,
20
are suspended from a front suspension system
23
. The front suspension system
23
includes, among other components, two straight swing arms
24
, one disposed on either side of the snowmobile
10
. The swing arms
24
connect to shock absorbers
26
.
The motor
14
operatively connects to an endless track
30
at the rear of the snowmobile
10
beneath a tunnel of the frame
12
. The endless track
30
propels the snowmobile
10
forward (or backward, as the case may be).
As illustrated in
FIG. 7
, a spindle
34
connects to the left ski
18
through a bridge
36
. The bridge
36
typically is an elongated U-shaped structure with a bottom portion
38
connected to the ski
18
. The spindle
34
and ski
18
are attached to the snowmobile front suspension system
23
via a spindle holder
56
, which is attached to a forward portion of the swing arm
24
. A rear portion of the swing arm
24
connects to the frame
12
via a pivot collar
58
and pin
60
. Connecting the swing arm
24
to the frame
12
of the snowmobile
10
in this manner serves at least two functions. First, the pivot collar
58
permits the swing arm
24
to pivot upwardly and downwardly, which allows the ski
18
to move up and down as the snowmobile
10
traverses the ground. The pivot collar
58
also holds the ski
18
in a generally fixed longitudinal position relative to the frame
12
so that the ski
18
does not move rearwardly during operation of the snowmobile
10
.
A bracket
62
attaches to the forward portion of the swing arm
24
at the location of the spindle holder
56
. The bracket
62
operatively connects to the frame
12
via upper and lower radius arm assemblies
64
and
66
. The upper and lower radius arm assemblies
64
,
66
serve at least two functions. First, they permit the swing arm
24
to pivot about the pivot collar
58
. This, in turn, permits the spindle
34
and ski
18
to move up and down relative to the frame
12
. Second, they keep the spindle
34
and ski
18
in a generally fixed lateral position with respect to a centerline
68
of the snowmobile
10
. In other words, the radius arm assemblies
64
,
66
prevent the ski
18
from collapsing laterally inwardly or outwardly during operation.
To cushion the forces experienced by the ski
18
as it traverses the ground (so that the forces are not transmitted to the rider), the shock absorber
26
extends between the bracket
62
and the frame
12
. The shock absorber
26
ensures that the frame
12
remains disposed above the ground. It also dampens any shocks encountered when the snowmobile
10
encounters rough terrain.
The swing arm
24
is normally constructed of sheet metal that is bent to form a straight hollow channel. Tubular swing arms constructed from metals and carbon fibers are also known. One common feature of all swing arms is their straight-line construction from the front of the swing arm to the rear of the swing arm. Because the front end of the straight swing arm
24
is disposed at the spindle
34
and is therefore close to the ground, an intermediate portion of the swing arm
24
has a low ground clearance that creates an obstruction for passing snow and other elements. When traveling in powder snow, the skis
18
,
20
tend to sink down into the snow and further reduce or eliminate the ground clearance of the swing arm
24
.
SUMMARY OF THE INVENTION
It is, therefore, an aspect of one or more embodiments of the present invention to provide an improved snowmobile swing arm construction.
According to another aspect of one or more embodiments of the present invention, a swing arm includes upward curves, steps, or angles that improve the swing arm's ground clearance.
According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having a bottommost point, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the bottommost point and the swing arm pivot axis.
The portion of the lower edge is spaced from the line by a distance that is preferably at least 2 cm, is more preferably at least 4 cm, and is even more preferably at least 6 cm.
The lower edge may be curved or angled. The lower edge may alternatively form a step.
The swing arm assembly may also include a pivot collar attached to the rear portion such that the pivot collar defines the swing arm pivot axis.
The swing arm assembly may also include a spindle holder attached to the forward portion. The spindle holder is constructed and arranged to pivotally receive a ski
The swing arm assembly may also include a bracket attached to the spindle holder. The bracket is adapted to receive at least one radius rod to attach the swing arm to a snowmobile.
The swing arm assembly may be combined with a snowmobile that includes a frame pivotally connected to the rear portion of the swing arm, a straddle-type seat supported by the frame, a steering ski supported by the front portion of the swing arm, and an endless track supported by the frame.
According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having an upper front tip, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the upper front tip and the swing arm pivot axis.
Additional and/or alternative aspects, features, and objects of the embodiments of the present invention will become apparent from the following drawings and detailed description.


REFERENCES:
patent: 3664446 (1972-05-01), Burtis et al.
patent: 3841649 (1974-10-01), McMullen
patent: 4699234 (1987-10-01), Shinozaki et al.
patent: 5332058 (1994-07-01), Bianco
patent: 5467839 (1995-11-01), Yoshio
patent: 2003/0159868 (2003-08-01), Alexander
Ski-Doo Parts Catalog, MX Z 800, (Nov., 1999).

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