AGRICULTURAL WAGON HAVING ALL-WHEEL STEERING

REMORQUE AGRICOLE A TOUTES ROUES DIRECTRICES

English Abstract

A wagon for agricultural use having an all-wheel steering mechanism. The wheels are hingedly attached to their respective axles. Steering alignment of the front wheels is provided by the wagon tongue, which is pivotally connected to the wagon frame and at least one of the front wheels. The front wheels are connected to each other by a steering linkage, consisting of two equal length members pinned to each other at a connection point. A front shaft crank is pivotally attached at the same connection point and rigidly attached to a rotatable shaft mounted with bearings to the underside of the wagon frame. Changes to the steering alignment of the front wheels causes lateral movement of the connection point, leading to rotation of the shaft and a corresponding direct change in alignment of the rear wheels, which are equipped with a similar system of linkages and cranks. This causes the front and rear wheels to follow the same path. Mounting the shaft above the axles increases ground clearance and mitigates the potential for damage to the steering mechanism. One of the axles may be pivotally attached to the wagon frame using a horizontal pin at substantially its midpoint, allowing angular pivoting of the axle in response to uneven terrain. The degree of pivoting is limited by stops integrally formed into the frame. The pivoting axle improves stability of the wagon, especially while turning and when transporting a top-heavy load.

French Abstract

Une remorque à usage agricole dotée d'un mécanisme « toutes roues directrices ». Les roues sont fixées à l'aide d'une charnière aux essieux respectifs. L'alignement de la direction des roues avant est assurée par le timon de la remorque, qui est raccordé de manière pivotante au châssis de la remorque et à au moins l'une des roues avant. Les roues avant sont reliées entre elles à l'aide d'une timonerie de direction, constituée de deux membres de même longueur fixés l'un à l'autre à un point de raccordement. Un vilebrequin avant est fixé de manière pivotante au même point de raccordement et solidement fixé à un arbre rotatif monté avec des roulements sous le châssis du wagon. Les changements de l'alignement de la direction des roues avant provoquent un mouvement latéral du point de raccordement, entraînant ainsi la rotation de l'arbre et un changement correspondant direct de l'alignement des roues arrière, équipées d'un même système de timoneries et de vilebrequins. Cela conduit les roues avant et arrière à suivre le même chemin. L'installation de l'arbre au-dessus des essieux augmente la garde au sol et réduit les risques d'endommagement du mécanisme de direction. L'un des essieux peut être fixé de manière pivotante au châssis de la remorque par le biais d'un axe horizontal situé sensiblement à son point médian, permettant ainsi un pivotement angulaire de l'essieu sur un terrain accidenté. Le degré de pivotement est limité par des arrêts intégralement formés dans le châssis. L'axe de pivotement améliore la stabilité de la remorque, principalement lors d'un virage et du transport d'une charge extrêmement lourde.

Claims

CLAIMS:
1. An agricultural wagon comprising:
a) a frame;
b) a front axle and a rear axle attached to the frame, each axle having
two ends;
c) front wheels pivotally attached to each end of the front axle and rear
wheels pivotally attached to each end of the rear axle;
d) a front steering linkage operably connected to the front wheels and a
rear steering linkage operably connected to the rear wheels;
e) a rotatable shaft operably interconnecting the front and rear steering
linkages above the front and rear steering linkages;
f) a front shaft crank and a rear shaft crank, each shaft crank rigidly
attached to the shaft proximal an end thereof, the front shaft crank
pivotally attached to the front steering linkage and the rear shaft crank
pivotally attached to the rear steering linkage; and,
g) the front wheels having a steering alignment, the front steering linkage
operable to act upon the front shaft crank, the front shaft crank rotating
the shaft, the rear shaft crank acting upon the rear steering linkage,
the rear steering linkage operable to effect a steering alignment of the
rear wheels complementary to the steering alignment of the front
wheels.
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2. The wagon of claim 1, wherein the wagon comprises a tongue pivotally
attached to the frame and connected to at least one of the front wheels,
pivoting of the tongue causing a change in the steering alignment of the
front wheels.
3. An agricultural wagon comprising:
a) a frame;
b) a front axle and a rear axle attached to the frame, each axle having
two ends;
c) front wheels pivotally attached to each end of the front axle and rear
wheels pivotally attached to each end of the rear axle;
d) a front steering linkage operably connected to the front wheels and a
rear steering linkage operably connected to the rear wheels;
e) a rotatable shaft operably interconnecting the front and rear steering
linkages above the front and rear steering linkages;
f) a front shaft crank and a rear shaft crank, each shaft crank rigidly
attached to the shaft, the front shaft crank pivotally attached to the
front steering linkage and the rear shaft crank pivotally attached to the
rear steering linkage;
g) a tongue pivotally attached to the frame and connected to at least one
of the front wheels; and,
h) the front wheels having a steering alignment, pivoting of the tongue
causing a change in the steering alignment of the front wheels, the
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front steering linkage operable to act upon the front shaft crank, the
front shaft crank rotating the shaft, the rear shaft crank acting upon the
rear steering linkage, the rear steering linkage operable to effect a
steering alignment of the rear wheels complementary to the steering
alignment of the front wheels.
4. The wagon of claim 3, wherein each shaft crank is attached to the shaft
proximal an end thereof.
5. The wagon of any one of claims 2 to 4, wherein the tongue is connected
to the front wheel by a pinned rod member connected to a forwardly
extending wheel crank.
6. The wagon of any one of claims 1 to 5, wherein the front axle is pivotally
attached to the frame to permit angular movement of the front axle in
response to uneven terrain.
7. The wagon of claim 6, wherein the front axle is pivotally attached to the
frame by a horizontal pin means at the midpoint of the axle.
8. The wagon of claims 6 or 7, wherein the angular movement of the front
axle is between 0 and 30 degrees with respect to horizontal.
9. The wagon of claims 6 or 7, wherein the angular movement of the front
axle is between 0 and 15 degrees with respect to horizontal.
10. The wagon of any one of claims 1 to 9, wherein the shaft extends
continuously between the front and rear wheels.
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11. The wagon of any one of claims 1 to 10, wherein each shaft crank is
mounted at an extremity of the shaft.
12. The wagon of any one of claims 1 to 11, wherein the shaft is journaled to
the underside of the frame.
13. The wagon of any one of claims 1 to 12, wherein the steering alignment of
the rear wheels is in the opposite direction to the steering alignment of the
front wheels.
14. The wagon of any one of claims 1 to 13, wherein the front and rear shaft
cranks are perpendicular to the shaft.
15. The wagon of any one of claims 1 to 14, wherein the front and rear shaft
cranks are vertical when the steering alignment is straight.
16. The wagon of any one of claims 1 to 15, wherein each wheel comprises a
vertical hinge member for pivotally attaching the wheel to its respective
axle and a horizontal spindle extending outwardly from the hinge member
for rotationally mounting the wheel.
17. The wagon of claim 16, wherein the front and rear steering linkages
comprise a wheel crank attached to each hinge member and a rod
member pivotally attached to each wheel crank, each rod member
pivotally attached to a front or rear shaft crank, respectively.
18. The wagon of claim 17, wherein each wheel crank of the front steering
linkage extends towards the rear of the wagon.
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19. The wagon of claims 17 or 18, wherein each wheel crank of the rear
steering linkage extends towards the front of the wagon.
20. An agricultural wagon comprising:
a) a frame;
b) a front axle pivotally attached to the frame to permit angular movement
of the front axle in response to uneven terrain and a rear axle fixedly
attached to the frame, each axle having two ends;
c) front wheels pivotally attached to each end of the front axle and rear
wheels pivotally attached to each end of the rear axle, the front wheels
having a steering alignment and the rear wheels having a steering
alignment complementary thereto;
d) a front steering linkage operably connected to the front wheels and a
rear steering linkage operably connected to the rear wheels; and,
e) a transmission linkage operably interconnecting the front and rear
steering linkages for translating the steering alignment of the front
wheels to the rear wheels.
21. The wagon of claim 20, wherein the front axle is pivotally attached to the
frame by a horizontal pin means at the midpoint of the axle.
22. The wagon of claims 20 or 21, wherein the angular movement of the front
axle is between 0 and 30 degrees with respect to horizontal.
23. The wagon of claims 20 or 21, wherein the angular movement of the front
axle is between 0 and 15 degrees with respect to horizontal.
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24. The wagon of any one of claims 20 to 23, wherein the transmission linkage
comprises a rotatable shaft longitudinally aligned with the frame, a front
shaft crank, and a rear shaft crank, each shaft crank rigidly attached to the
shaft, the front shaft crank pivotally attached to the front steering linkage
and the rear shaft crank pivotally attached to the rear steering linkage.
25. The wagon of claim 24, wherein the front steering linkage is operable to
act
upon the front shaft crank, the front shaft crank rotating the shaft, the rear
shaft crank acting upon the rear steering linkage, the rear steering linkage
operable to effect a steering alignment of the rear wheels complementary to
the steering alignment of the front wheels.
26. The wagon of claims 24 or 25, wherein the shaft is above the front and
rear
steering linkages.
27. The wagon of any one of claims 24 to 26, wherein the shaft extends
continuously between the front and rear wheels.
28. The wagon of any one of claims 24 to 27, wherein the shaft is journaled to
the underside of the frame.
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Description

CA 02360469 2001-10-30
Title: Agricultural Wagon Having All-Wheel Steering
Inventor: Anthony M. Platteeuw, Ernest L. Wilson
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a wagon for agricultural use having an all-
wheel steering mechanism. Specifically, the invention relates to an all-wheel
steering mechanism for a four-wheeled wagon for use in the nursery industry.
Prior Art
In the nursery industry, it is common practice to use various types and sizes
of
wagons for the day to day transportation of plants and materials. Often the
layout of the nursery is such that there is little room for these wagons to
maneuver safely, without destroying nursery stock.
In general, wagons are designed with two-wheel steering. These wagons have a
steerable set of front wheels, and a set of back wheels which are fixed in the
forward direction. The steerable front wheels of the wagon are attached to a
wagon tongue, which is attached to a tow vehicle. Turning the tow vehicle
pivots
the tongue, turning the front wheels of the wagon. The inherent problem with
this
design is that when turning, the back wheels follow a shorter path than the
front
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CA 02360469 2001-10-30
wheels, which requires the operator to make a wide turn to prevent destruction
of
the nursery stock while turning. This problem becomes more noticeable among
longer length wagons, where a great deal of room is required at the end of the
row to allow the wagon to turn safely.
One solution to this problem is to steer both the front and back wheels of the
wagon. This is preferably accomplished by a mechanism that translates the
steering alignment of the front wheels to the back wheels. Generally, as the
front
wheels are turned in a certain direction, the back wheels are designed to turn
in
the corresponding opposite direction. The result is that the back wheels
follow in
the same path as the front wheels, effectively allowing the wagon to be turned
in
a much shorter distance.
A known mechanism used to translate the steering alignment to the rear wheels
uses diagonal tie bars attached to the front and rear axles. One member is
attached to the left side of the front axle, and the right side of the rear
axle;
whereas, the other member is attached to the right side of the front axle and
the
left side of the rear axle. As a result, as the front axle is steered in one
direction
by the tongue, the rear axle is steered in the opposite direction by the
diagonal
members. While this method accomplishes the desired four wheel steering
action, it also has drawbacks. For example, as the diagonal members must be
positioned at the level of the wheel axles, it seriously limits the ground
clearance
of the wagon. This exposes the steering mechanism to potential damage from
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CA 02360469 2001-10-30
obstructions. This method also has limitations as to the precision of the
steering
alignment, as a small imprecision in the placement of the diagonal members
will
result in a substantial difference between front and rear steering.
Another drawback associated with all-wheel steered wagons is their tendency
towards tipping. This is especially prevalent when turning the wagon sharply
on
uneven terrain or with a top-heavy load. It is therefore desirable to provide
means to enhance the stability of the wagon, especially over uneven terrain.
BRIEF SUMMARY OF THE INVENTION
According to this invention, there is provided an all wheel steerable wagon,
that
has a frame with attached front and rear axles. The axles have wheels
pivotally
attached to their ends. A front steering linkage is operably connected to the
front
wheels for tracking their steering alignment and a rear steering linkage is
operably connected to the rear wheels. A transmission linkage is attached to
the
underside of the frame, operably inter-connecting the front and rear steering
linkages, for translating the steering alignment of the front wheels to the
rear
steering linkage to impart a complementary steering alignment to the rear
wheels, where the imparted steering alignment is a direct function of the
steering
alignment of the front wheels.
The transmission linkage consists of a shaft. The operable interconnection
between the front steering linkage and the shaft rotates the shaft in response
to
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CA 02360469 2001-10-30
movement of the front steering linkage. The operable interconnection between
the shaft and the rear steering linkage moves the rear steering linkage in
response to rotation of the shaft. Each steering linkage consists of a rod
member
and each operable interconnection consists of a crank fixedly attached to the
shaft and pivotally attached to each rod member. The shaft is centrally
mounted
along the longitudinal axis of the wagon and each rod is aligned transversely
to
the shaft.
The front axle is connected to the frame of the wagon by a horizontal pin at
substantially the midpoint of the axle, allowing the axle to pivot angularly
about
the pin in response to uneven terrain. The frame has stops integrally formed
into it that are operable to limit the angular pivoting of the axle to thirty
degrees
by contact of the axle with the stops.
Further features of the invention will be described or will become apparent in
the
course of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more clearly understood, a preferred
embodiment thereof will now be described in detail by way of example, with
reference to the accompanying drawings, in which:
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CA 02360469 2001-10-30
Fig. 1 is a perspective view of an embodiment of the present invention.
Fig. 2 is a top view of an embodiment of the present invention.
Fig. 3 is a top view of an embodiment of the present invention, with the
wheels
aligned in a turning position.
PREFERRED EMBODIMENT
Referring to the accompanying diagrams, a preferred embodiment of the
invention is now described.
FtG. 1 shows one embodiment of an all-wheel steerable wagon according to the
present invention. The wagon has front (1 ) and rear (2) axles, attached to
the
underside of the wagon frame (not shown) by means of vertical frame members
extending downwardly from the frame (3). C-shaped hinge members (4, 5) are
connected to both ends of each axle by means of a vertical pin, permitting
horizontal rotation or pivoting of the hinge. Extending outwardly from each
hinge
member is a spindle for mounting a wheel (not shown).
In order to steer the wheels, wheel cranks (6, 7) are fixedly attached to each
hinge member and forms part of the steering mechanism as will be described
hereinafter. The wheel cranks attached to the front hinges (6) extend towards
the rear of the wagon, whereas, the wheel cranks attached to the rear hinges
(7)
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CA 02360469 2001-10-30
extend in the opposite direction towards the front of the wagon. In each case,
the wheel cranks are in turn connected to one another by means of steering
linkages (8, 12). The cranks thereby provide leverage for turning the wheels
in
response to a parallelogram movement of the steering linkage.
The front steering linkage (8) consists of two rod members of equal length
that
are pinned (9) at their ends to one another and to their respective hinges at
their
opposite ends (10, 11 ). In principle, steering of the wheels is accomplished
by
lateral movement of the connection point identified at 9, which causes the
steering linkage to act on the wheel cranks, thereby pivoting the hinges and
effecting steering alignment of the wheels. The rear steering linkage (12) is
similarly constructed and functions in a similar manner, as can be seen from
the
figure.
A longitudinal shaft (13) connecting the front and rear steering linkages is
mounted using brackets (14, 15) bolted to the underside of the wagon frame.
The brackets are positioned at the ends of the shaft and contain bearings
which
allow the shaft to rotate within the brackets. Attached to the extremities of
the
shaft are front (16) and rear (17) shaft cranks by means of a rigid
connection.
The opposite ends of the shaft cranks are pivotally attached to their
respective
steering linkages at the connection points of the rods, 9 and 18.
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CA 02360469 2001-10-30
Lateral movement of the front steering linkage connection point at 9 in
response
to a change in steering alignment causes the front shaft crank (16) to pivot,
thereby causing a corresponding and direct rotation of the shaft (13). The
shaft
functions as a transmission linkage to translate the steering alignment of the
front
wheels to the rear wheels. The rear shaft crank (17) is parallel to the front
shaft
crank (16) and rotates with the shaft, thereby effecting a corresponding
lateral
movement of the rear steering linkage connection point at 18 in the same
direction. Since the front (6) and rear (7) wheel cranks extend from the wheel
hinges in opposite inward directions, the lateral movement of the rear
steering
linkage (12) causes the rear wheels to adopt a complementary steering
alignment opposite in direction to that of the front wheels. This allows the
rear
wheels to follow a similar path to the front wheels throughout the turn.
The steering alignment of the front wheels of the wagon is determined by the
position of the wagon tongue (19), which is pivotally connected by a vertical
pin
(20) to the frame housing the front axle (21 ). This allows the wagon tongue
to
pivot horizontally in response to changes in direction of the towing vehicle
(not
shown). A pinned rod member (22) is provided connecting the tongue to a
forwardly extending wheel crank (23) attached to one of the front wheel
hinges.
Pivoting of the wagon tongue causes the attached front wheel hinge to pivot in
the same direction, thus causing a corresponding change in steering alignment
of
the front wheels. The rear wheels assume a complementary steering alignment
due to rotation of the shaft as previously described.
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CA 02360469 2001-10-30
The front axle (1) is attached at substantially its midpoint to the frame
housing
the front axle (21 ) by a horizontal pin (24), permitting angular pivoting of
the front
axle. This allows the wagon to overcome tipping problems associated with
turning over uneven terrain, or otherwise while turning when transporting a
top-
heavy load. The frame housing the front axle (21 ) has horizontal stops (25)
which are integrally formed into the frame. The stops are designed to limit
the
degree of pivoting of the front axle (1). The stops in the preferred
embodiment
shown limit the maximum degree of pivoting to thirty degrees, but more
typically,
the axle pivots less than fifteen degrees in response to typically uneven
terrain.
Fig. 1 will now be described with reference to the arrows indicating the
direction
of movement of the parts in response to a change in steering alignment. The
forward direction is the direction that the wagon would be towed by a vehicle
attached to the wagon tongue (not shown). In context of the description of the
figures, "push" indicates a force placing the member being pushed in
compression, whereas "pull" indicates a force placing the member being pulled
in
tension.
Looking in the forward direction, the arrow (26) indicates a left turn of the
wagon
tongue (19). The wagon tongue (19) will pivot to the left, pushing the
attached
rod member (22) connected to the forwardly extending wheel crank of the left
front wheel (23). This causes the left front wheel to horizontally pivot in a
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CA 02360469 2001-10-30
counter-clockwise direction (27), as viewed from above. The steering linkage
connecting the front wheels (8) moves laterally to the right, causing the
right front
wheel to similarly horizontally pivot (28).
The front shaft crank (16), pivotally attached to the front steering linkage
(8) at
the point of connection of the two rod members (9), pivots counter-clockwise,
as
viewed when facing the forward direction. This causes a counter-clockwise
rotation (29) of the shaft to which it is perpendicularly and fixedly
attached,
producing a corresponding rotation of the rear shaft crank (17).
The rear shaft crank (17) is pivotally attached to the rear steering linkage
(12).
The rear steering linkage (12) translates to the right, causing a clockwise
rotation
of both of the attached rear wheels (30, 31 ). This causes the rear wheels to
follow substantially the same path as the front wheels throughout the turn.
Fig. 2 shows a top view of the wagon wheels when traveling straight ahead. The
wagon tongue (19) is shown, pivotally connected to the frame housing the front
axle (20) and connected to the left front wheel by a pinned rod member (22)
attached to the forwardly extending wheel crank (23).
The change in steering alignment is illustrated with reference to Fig. 3,
which
shows a top view of the wagon wheels positioned for a left turn. The front
steering linkage (8) has moved to the right, causing pivoting of the front
shaft
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CA 02360469 2001-10-30
crank (16) to the right in turn, causing counter-clockwise rotation (32) of
the shaft
(13) as shown. The rotation of the shaft translates the steering alignment to
the
rear wheels by means of the rear shaft crank (17) and movement of the rear
steering linkage (12). The rear wheels correspondingly turn in the opposite
direction to the front wheels.
From the foregoing, it will be seen that this invention is one well adapted to
attain
all the ends and objects hereinabove set forth together with other advantages
which are obvious and which are inherent to the structure.
It will be understood that certain features and sub-combinations are of
utility and
may be employed without reference to other features and sub-combinations.
This is contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of the invention without
departing from the scope thereof, it is to be understood that all matter
herein set
forth or shown in the accompanying drawings is to be interpreted as
illustrative
and not in a limiting sense.

Representative Drawing