ENSEMBLE DE TRACTION POUR VEHICULE TOUS TERRAINS

ASSEMBLY ON A TERRAIN-TRAVELLING MOTOR VEHICLE

Abrégé anglais

A B S T R A C T
A terrain-traveling motor vehicle has twin
tracks and bogie assemblies pivotally attached to the frame
of the vehicle, comprising a rear pair of drive wheels mounted
on the frame of the vehicle and a pair of front wheels each of
which is supported on a pivotable belt-tensioning arm disposed
on the forward end of a bogie arm found on each bogie assembly,
the rearward end of said arm being supported by means of shaft
journals proximate to and in front of the center axis of the
pair of rear wheels. The bogie arms are movable in the vertical
plane by means of first hydraulic pressure cylinders controllable
from the cab of the vehicle for upward and downward pivoting of
the bogie assemblies simultaneously or independently of each
other, and for tautening the bogie tracks. The belt-tensioning
arms are movable independently of the bogie arms by means of
respective second hydraulic pressure cylinders which are pressurized
at a desired adjustable pressure for maintaining a desired
tautness in the belt during the pivoting movement of the bogie
arm, as well as during the continual changes in the configuration
of the lower perimeter of the belt which arise as the track passes
over irregular ground terrain.

Revendications

The embodiments of the invention in which an
exclusive property of privilege is claimed, are defined as
follows:
1. An assembly on a terrain-traveling motor vehicle
having twin tracks and bogie assemblies pivotally attached to
the frame of the vehicle and comprising a rear pair of drive
wheels mounted on the frame of the vehicle, and a front pair
of wheels wherein each said front wheel is supported on a
pivotable belt-tensioning arm at the forward end of a bogie
arm for each bogie assembly, the rearward end of said arm
being supported by means of shaft journals proximate to and in
front of the center axis of the rear pair of wheels, the belt-
tensioning arms and bogie arms being movable in the vertical
plane by means of first hydraulic pressure cylinders controllable
from the cab of the vehicle, for pivoting the bogie assemblies
upwardly and downwardly simultaneously or independently of
each other and for tautening the bogie tracks, and a second
hydraulic cylinder for moving each belt-tensioning arm
independently of the respective bogie arm,each said second
hydraulic cylinder pressurized at a desired adjustable pressure
for maintaining a desired tautness in the belt during the
pivoting movement of the bogie arm as well as during the continual
changes in configuration of the lower perimeter of the track
which occur as the vehicle drives over irregular ground terrain.
2. An assembly according to claim 1, in which the second
pressure cylinder is disposed on the top side of the bogie arm
with one end thereof supported on the forward part of the bogie
arm, and the other end thereof supported on an extension of the
belt-tensioning arm which extends upwardly from the support of said
arm on the bogie arm.

Description

1~'7~
_ The present invention relates to an assembly on a
terrain-traveling motor vehicle having tw:Ln CATERPILI,A~*tracks
and bo~ie assemblies pivotally attached to the frame of the
vehicle, as recited in the preamble of the appurtenant claim l.
A terrain-traveling motor vehicle of this type is
known from Swedish Patent 194,059, which shows a vehicle with
a pair of bogie assemblies, usually known as half-tracks, where-
in the rear wheels are supported on the frame of the vehicle
and the bogie arm for the bogie assembly is supported in front
10 of and somewhat below the central axis of the rear wheels.
The front wheel of the bogie assen~ly is supported on a belt-
tensioning arm rotatably mounted on the forward end of the
bogie arm. Each bogie assembly is provided with a hydraulic
pressure cylinder, which is connected to said belt-tensioning
arm and to the frame of the vehicle. When this pressure
cylinder is pressurized and extended, the belt-tensioning arm
is pivoted, whereby the belt is tautened about tha front and
rear wheels of the bogie assembly, and upon further extension
of the pressure cylinder the bogie assembl~ is pivoted
20 downward
A drawback of the above arrangement is that it is
not possible to maintain a certain desired tautness in the
belt if at the same time as the bogie assembly, by means of
the pressure cylinder acting upon the bogie arm, is pivoted up
25 and down, the forward portion of the vehicle, which is provided
with front wheels, is simultaneously raised by the front wheels
lifting up from the ground. In such circumstances, the taut-
ness of the belt is completely dependent upon the force that
is needed to lift the forward part of the vehicle up from the
30 ground, so that the degree of tautness may be greater than
desired. In normal driving, on the other hand, where the
bogies operate as half-tracks and the front wheels rest on
the ground,`it is possible by means of the pressure cylinder
to maintain a aesired track tautness/ but it is not possible
35 to pivot the bogie downwardly and thereby raise the vehicle
without increasing the track tautness~
The ob~ect of the present invention is to provide a
terrain-traveling vehicle in which the body of the vehicleg
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and optionally the bogle arms :independently of each o-ther, may
be raised and lowered for maintaining a desired position of the
vehicle body as the vehicle traverses irregular ground surfaces,
without this afEecting the tautness of the belt.
This object is achieved in accordance with the
present invention by means of the characterizing features
disclosed in the characterizing clause of the appurtenant
claim 1. By means of the second pressure cylinder recited therein,
which acts upon the belt-tensioning arm, a certain desired track
tautness can be maintained by causing this pressure cylinder
to be pressurized at a desired determined pressure. The track
tautness can at all times be decreased or increased by regulating
said pressure, independently of the ground surEace conditions
and independently of the up-and-down pivoting movements of the
bogie assembly effected by means of the first pressure cylinder.
In general, the terrain-traveling motor vehicle
having twin tracks and bogie assemblies pivotally attached to
the frame of the vëhicle comprises an assembly on a terrain-
traveling motor vehicle having twin tracks and bogie assemblies
pivotally attached to the frame of the vehicle and comprising
a rear pair of drive wheels mounted on the frame of the vehicle,
and a front pair of wheels wherein each said front wheel is
supported on a pivotable belt-tensioning arm at the forward end
of a bogie arm for each bogie assembly, the rearward end of
said arm being supported by means of shaft journals proximate to
and in front of the center axis of the rear pair of wheels, the
belt-tensioning arms and bogie arms being movable in the
vertical plane by means of first hydraulic pressure cylinders
controllable from the cab of the vehicle, for pivoting the bogie
assemblies upwarclly and downwardly simultaneously or

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3.
independently of each other and for tautening the bogie
tracks, and a second hydraulic cylinder for moving each
belt-tensioning arm independently of the respective
bogie arm each said second hydraulic cylinder pressurized at
a desired adjustable pressure for maintaining a desired
tautness in the belt during the pivo-ting movement of the
bogie arm as well as during the continual changes in configuration
of the lower perimeter of the track which occur as the vehicle
drives over irregular ground terrain.
More specifically, the second pressure cylinder
is disposed on the top side of the bogie arm with one end
thereof supported on the forward part of the bogie arm, and
the other end thereof supported on an extension of the belt-
tensioning arm which extends upwardly from the support of
said arm on the bogie arm.
An embodiment example of a terrain-travelling
motor vehicle in accordance with the invention will be
described in greater detail in the following with reference to
the accompanying drawings, wherein
Figures 1 and 2, respectively, show the motor
vehicle as seen from the side and from the top.
The terrain-traveling motor vehicle 1 is provided
with twin CATERPILLAR* tracks and bogie assemblies 2, wherein
the rear wheel 5 of each bogie assembly is supported in the
frame of the vehicle 1 and the front wheel 7 of each assembly
is supported on a respective pivotable arm 9 provided at the
forward end of the bogie arm 8 found on each bogie assembly,
the rearward end of said arm 8 being supported by means of
shaft journals 4 proximate to and in front of the center of
the rear wheels 5. The arm 9 is movable by means of a pressure
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cylinder 10 which is pressurized at a deslred, ad~ustable
pressure Eor maintaining a desired tau-tness in the bogie
track during the pivoting movement of the bogie arm 8,
as well as during the continual changes in the lower
perimeter of the track as the ~ehicle drives over uneven
terrain. The bogie assemblies 2 are independently and/or
mutually pivotable and adjustable in relation to each other
in the vertical plan by means of pressure cylinders 6 which
are controlled from the cab
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_ of the vehicle. Approximately midway be-tween the front and
rear wheels 7,5, a track support wheel 11 is supported on the
bogie arm 8, said wheel 11 preferably having a smaller diameter.
than the front and rear wheels 7,5 and resting against the
lower perimeter of the belt. This means that when the bogie
assemblies are in the normal position shown in Figure 1, the
lower perimeters of all of the wheels will rest against a level
surface, i.e., the front and rear wheels 7,5 and the belt-
supporting wheel 11 in each bogie assembly have a common
10 tangent. Since the bogie arm 8 is eccentrically supported at
4 in relation to the central axis of the rear wheel 5, i.e.,
in front of and somewhat below said center axis, the bogie
track will slacken when the bogie arm 8 is pivoted upwardly by
means o~ the pressure cylinaer 6. The slack is taken up by
the belt-tensioning arm 9 which pivots the front wheel 7
forwardly, owing to the fact that the pressure cylinder 10 is
pressurized at a desired pressure in a manner known per se;
~n this manner,.the.pressure cylinder 10 which is connected to
the extension of the belt-tensioning arm 9 maintains the
20 desired tautness in the track whether the belt slackens as the
bogie arm 8 is pivoted upwardly or tautens as the bogie arm 8
pivots downwardly, or as the lower perimeter of the track ~s
subjected to changes in.configuration as the track passes over
irrPgularities such as roots and rocks in the ground terrain.
The front and rear wheels 7 and 5 preferably have
the same diameter, so that the vehicle, in reasonably even
terrain, moves equally well forward or backwards. If the
vehicle is driving over very rough terrain, the bogie assemblies
can be pivoted upwardly and downwardly independently of each
30other, and thereby compensate for any disparity in level when
traversing sloping terrain so that the frame ana cab of the
vehicle are maintained.approximately.level, and the bogie
assemblies can also be rai~ad and lowered as required for pass-
ing over small hills or depressions in the ground on one side
35or the other of the vehicle, as known per se.
In the practical configuration of the bogie arm 8
which is shown in Figure 1, the arm is supported at 4 in the
frame 3 of the vehicle at a height above the ground corresponding
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I.~.'~.a,~
- to the diameter of -the belt-tensioning wheel 11, whereby the
rearward part oE the bogie arm 8 is parallel with the ground
surface in the normal driving position of the bogie assemblies
shown in Figure 1. From the middle portion of the arm, where
5 the belt-tensioning wheel is mounted, the bogie arm 8 extends
on an upward incline to a height above the ground approximately
corresponding to the s~ of the diameter of the front whe~l 7
and the length of the belt-tensioning arm 9, which extends
approximately straight down from its support 14 at the forward
10 end of the bogie arm 8.
The drive member or pressure cylinder 10 or pivoting
the belt-tensioning arm 9 so as thereby to maintain the aesired
tautness of the belt consists of a hydraulic cylinder 10' with
piston 10" arranged on the top side of the bogie arm 8, the
15 end of the cylinder 10' being supported at 12 on the forward
part 8' of the bogie arm, and the piston/piston rod 10" being
supported at 13 on an extension of the belt-tensioning arm 9
which extends upwardly from the arm support 14 on the bogie
arm 8.
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