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Description  |
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SUMMARY OF THE INVENTION
The invention relates vehicles included in the group which comprises
tractors, motorcars, soil cultivating machines, trucks, wagons and the
like, wherein such vehicles comprise at least one track arranged around
the vehicles' ground wheels.
According to one aspect of the invention the track comprises a belt of
flexible material and has a plurality of profiles, ridges or the like
which are directed forwardly with respect to the direction of rotation of
the track for forward travel of the vehicle and connecting means for
connecting implements to the vehicle.
For a better understanding of the invention, and to show how the same may
be carried into effect, reference will be made, by way of example, to the
accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a tractor to which the invention is applied,
FIG. 2 is a plan view of the tractor shown in FIG. 1,
FIG. 3 is a side elevation to an enlarged scale, as seen in the direction
of an arrow III in FIG. 2 and shows part of an endless tread track of the
tractor in contact with the ground,
FIG. 4 is a section taken on the line IV--IV in FIG. 3,
FIGS. 5 to 9 show alternative embodiments as seen in the direction of the
arrow III in FIG. 2,
FIG. 10 is a section taken on the line X--X in FIG. 9,
FIG. 11 which is partly in section, illustrates an embodiment of an endless
tread track that is suitable for a plurality of vehicle wheels, again as
seen in the direction of the arrow III in FIG. 2,
FIG. 12 is a section taken on the line XII--XII in FIG. 11,
FIGS. 13 and 14 show further alternative embodiments of the endless tread
track,
FIG. 15 is a side elevation of a further tractor in accordance with the
invention,
FIG. 16 is a plan view of the tractor of FIG. 15,
FIG. 17 is a side elevation, to an enlarged scale, of part of the rear of
the tractor as seen in the direction of the arrows XVII--XVII in FIG. 16,
and
FIG. 18 is a part sectional elevation taken on the line XVIII--XVIII in
FIG. 17.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2 comprise a frame 1 to which a driving engine 2 is secured at
the front, said engine 2 driving, by means of a gear transmission 3 and an
auxiliary shaft 4, a rear axle 5 through a differential 6. The rear axle 5
has on each side of the tractor two rear wheels 7 located side by side and
being provided with tires. The diameters of the rear wheels 7 are equal to
one another. The tractor is furthermore provided with a central axle 8
located in front of the rear axle 5 and parallel to the latter. The
central axle 8 is rigidly secured in place with respect to the tractor
frame 1. The central axle 8 also has, on each side of the tractor two
tired central wheels 9 arranged side by side and having diameters equal to
those of the rear wheels 7. Considered in the direction A, the rear wheels
7 are in line with and behind the wheels 9.
At the area of the central axle 8, a support 10 is provided on either side
of the tractor on the frame 1, said support 10 extending upwardly from the
axle 8 and supporting a pivotal shaft 11 at an area located
perpendicularly above the axle 8, the center line of said shaft 11 being
horizontal and perpendicular to the direction A. On each side of the
tractor, the frame 1 has fastened to it a pivotal shaft 12, which also
extends horizontally and perpendicular to the direction A. In the side
view of FIG. 1, the pivotal shaft 12 is located just in front of the
foremost points of the central wheels 9. With each pivotal shaft 12 is
rigidly connected a short arm 13 extending approximately vertically
upwards from the pivotal shaft 12 in the normal operational state. At the
end remote from the pivotal shaft 12, each arm 13 has a pivotal shaft 14
extending parallel to the pivotal shaft 11. About the pivotal shaft 14 is
pivotable the piston rod of a hydraulic cylinder 15, the cylinder itself
being pivotable about the shaft 11.
Each pivotal shaft 12 has also rigidly secured to it an arm 16 which
extends forwardly and slightly upwardly from the pivotal shaft 12,
considered in the direction of travel A. The front ends of the two arms
16, located one on each side of the tractor frame, are each provided with
a pivotal shaft 17 extending horizontally perpendicular to the direction
A. About each pivotal shaft 17 is pivotable an arm 18 which extends
approximately vertically downwards in the normal operational state. The
lower end of each arm 18 is provided with a horizontal pivotal shaft 19
extending perpendicular to the direction A. At an area located between the
shafts 12 and 17, the bottom of each arm 16 is provided with a pivotal
shaft 20, which is parallel to the corresponding pivotal shaft 19. To each
pivotal shaft 19 is pivoted the piston rod of a corresponding hydraulic
cylinder 21, the cylinder 21 itself being pivotable about the respective
pivotal shaft 20. The distance between he center lines of the shafts 12
and 17 is about four times the distance between the shafts 12 and 14 and
about three times the distance between the shafts 17 and 19.
The hydraulic cylinders 15 and 21 communicate with the hydraulic system of
the tractor and can be actuated from a driver seat 22 located, viewed from
a side (FIG. 1) approximately above the region between the axles 5 and 8.
Each of the parts of the hydraulic system communicating with the hydraulic
cylinders 15 and 21 may include a hydro-pneumatic or other pressure
accumulator.
To the lower end of each arm 18 is furthermore secured a front wheel axle
23, the center lines of the front axles 23 and of the pivotal shafts 19
being coincident. These two shafts may be integral with one another. Front
wheels 24 with tires are freely rotatable about the front axles 23. The
diameters of all the front wheels 24 are equal to those of all the wheels
7 and 9. The central wheels 9 are freely rotatable about the central axles
8.
The tractor shown in FIGS. 1 and 2 comprises furthermore a three-point lift
25 fastened to the tractor near the driven rear axle 5. The weight of the
driving engine 2 and of the gear box 3 bears principally on the front
wheels 24.
The front wheels 24 also comprise, on each side of the tractor, two tired
wheels arranged side by side so that, considered in the direction A, the
front wheels 24, the central wheels 9, and the rear wheels 7 are in line
one behind the other.
About each of the three pairs of wheels 7, 9, 24 on each side of the
tractor is passed an endless tread track 26, the width of which
approximately corresponds with the overall width of two neighboring tired
wheels. The width of the track is about fifty centimeters (192/3 inches).
Track 26 comprises an endless belt 27 of synthetic resin or rubber-like
material or both which may be reinforced by nylon or canvas liners or by
steel wiring or a combination thereof. The flexible endless belt 27 covers
the whole width of track 26. From FIGS. 3 and 4 it is apparent that the
flexible belt 27 is provided on its inner surface in the installed state
with a large number of equidistant metal strips 28 covering the width of
the belt. In the sectional view of FIG. 4, each strip 28 joins the surface
of the flexible belt 27 throughout the width of the outer surface of the
tire at the areas where the outer surfaces of the tires of the wheels come
into contact with track 26. Midway across the width of each strip 28, an
inward extension 29 is formed in the shape of an inverted V and is
integral with the flat parts of the strip 28 on either side. The width of
each extension 29 is such that it fits in the space between the belts of
each pair of wheels fastened to one axle. As seen in FIGS. 3, 5 and 9, the
length of said extension 29 is the same as the distance between successive
extensions 29. On the inner surface, that is to say, on the side facing
the wheel axles, each extension 29 has a rubber coating 30 which is
secured thereto by vulcanization.
On the outer surface of the flexible belt 27, that is to say, on the side
remote from the wheel axles in the installed state, a number of profiles
31 are provided, the number being equal to the number of strips 28, and
considered in the direction of length of the belt 27, each profile 31 is
fastened at an area on the belt 27 where a strip 28 is located.
Each profile 31 comprises two U-shaped rolled profiles 32, the webs of
which are arranged back-to-back where they may be welded to one another,
whereas the flanges extend forwardly and rearwardly, respectively,
relative to the direction A. The profile 31 covers the whole width of the
belt 27. The two flanges which engage the bottom of the belt 27 have
bores. At corresponding areas the belt 27 and also the opposite strips 28
also have bores for receiving bolts 33 so that heads of the bolts are
located on the tops of the strips 28, whereas the co-operating nuts are
located between the flanges of the profiles 32. The profiles 32 are thus
each fastened by means of two rows of the bolts 33 which rows are spaced
apart and located side by side, viewed in side elevation, together with
the associated strips 28, to the flexible belt 27. The width of the flange
of each of the profiles 32 is approximately equal to half the width of the
associated strip 28 so that the width of the ground-contacting flat bottom
of each profile 31 is substantially equal to the width of one of the
strips 28. The distance between two profiles 31, and between two strips 28
measured lengthwise along the belt 27, is substantially equal to the width
of one end of the profiles 31 and one of the strips 28.
In the embodiment shown in FIG. 5, the belt 27 is provided on the surface
remote from the wheels is provided with gutter-shaped or channel-section
profiles 34 each consisting of a single length of rolled steel covering
again the whole width of the belt 27. Each profile 34 has a web 35 which
fully engages the belt 27 and which has a width equal to the width of the
opposite strip 28 or a width slightly greater than the latter. The two
longitudinal edges of the web 35 join limbs 36 which extend perpendicular
to the web 35 and to the belt 27. The end edges of the limbs 36 that are
remote from the web 35 terminate in flanges 37 which are parallel to the
web 35, one flange extending to the front from the limb 36 concerned,
considered in the direction A and the other flange 37 extending to the
rear. The profile 34 is again secured to the belt 27 by two rows of the
bolts 33 and to the strips 28, whereas the nuts screwed onto said bolts
are located between the limbs 36. The neighboring ends of the bolts 33 are
located at a distance from the outer edges of the limbs 36. The width of
the limbs 36 and of the flanges 37 are approximately equal to half the
width of the web 35. For certain purposes it is advantageous to use a
narrower profile, in which case the width of the web is approximately
equal to the width of the associated limbs 36 and of the associated
flanges 37, as is shown in FIG. 6. In this embodiment the profile 38 may
be secured by only one row of bolts 33 to the belt 27 and to the strips
28, in which case the profile has a greater movability.
In the embodiment shown in FIG. 7, the profile 39 comprises a web 40, which
fully engages the belt 27 and which has a width approximately equal to, or
slightly greater than, the width of the strip 28 on the other side of the
belt 27. Considered in the direction A, the front edge of the web 40 has a
limb 41 at right angles to the web 40 and to the belt 27 so as to extend
away from the belt 27. The width of the limb 41 is substantially equal to
half the width of the web 40. The limb 41 joins a flange 42 extending
parallel to the web 40 and to the belt 27 and away from the limb 41 in a
direction opposite the direction A or, on other words, extending from the
limb 41 in the direction of movement or rotation of the region of track 26
located on the ground with respect to the frame. The width of the flange
42 is about three quarters of the width of the web 40. The profile 39 is
secured by two adjacent rows of bolts 43 to the belt 27 and to the strip
28. The nuts screwed onto the bolts 43 are located in the space between
the web 40 and the flange 42.
In the embodiment shown in FIG. 8, the side of the belt 27, that is remote
from the wheels is provided with a profile 44 having a web 45 which
engages the belt 27 and which has a width approximately equal to, or
slightly greater than, the width of the strip 28. The two end edges of the
web 45 merge into limbs 46 which are at right angles to the web 45 and
also to the belt 27, while the edges of the two limbs that are remote from
the web 45 have flanges 47, which, in contrast to the embodiment shown in
FIG. 5, both project from the associated limbs 46 opposite to the
direction A and in the direction of rotation with respect to the frame.
The profile 44 is secured to the flexible belt 27 and to the associated
strip 28 by two rows of bolts 48, whereas the nuts screwed onto said bolts
48 and engaging the web 45 are located inside the profile 44 as in the
preceding embodiments.
The profiles shown in the preceding embodiments are all rolled profiles.
FIGS. 9 and 10, however, show profiles 49 of forged material. The profiles
49 have essentially an I-shaped cross-section, a top flange 50 having a
width approximately equal to the width of the strip 28 located on the
other side of the belt 27. A web 51 joining the center of the flange 50 is
at right angles to that flange 50 and to the belt 27 itself and is
provided, at the end remote from the flange 50, with a flange 52 extending
on either side, the outer surface of which flange 52 is slightly
cylindrically curved (see FIG. 9). The flange 52 is directly supported by
means of a number of lateral partitions 53 on either side of the web 51 on
the flange 50 and on the web 51. The lateral partitions 53 are at right
angles to the direction of the length of the profile 49 and are spaced
apart by equal distances. The flanges 52 and 50, the web 51 and the
lateral partitions 53 are forged integrally from a single piece of
material. The profiles 49 are preferably treated thermally so that at
least their flanges 52 are hardened. The profiles 49 are secured by two
rows of bolts 54 to the belt 27 and to the associated strips 28. The nuts
of said bolts are covered on the lower side as seen in FIGS. 9 and 10 by
the associated flanges 52.
FIGS. 11 and 12 shown an embodiment in which track 26 is suitable for a
vehicle having only one tired wheel at each end of each axle. The surface
of the flexible belt 27 facing the wheels is provided for this case with a
large number of strips 55 which engage the surface of the flexible belt
facing the wheels over a width equal to the width of the tires. At both
ends of each strip 55, an extension 56 is provided in the form of an
inverted V as shown in FIG. 12 so that the sloping surface of the
extension facing the wheel fits one side of each co-operating tire. The
outer end of each extension 56 is bent back towards the center of the belt
and is in contact with the surface of the belt 27. These bent-back parts
of the extensions 56, as well as the flat central part of the strip 55,
are secured by bolts 57 to the belt 27 and to a profile 58 on the other
side of the belt 27. Each profile 58 comprises a rolled steel I-profile 59
which is vulcanized to, and completely embedded in, a layer 60 of flexible
material, for example, rubber. The nuts on the two rows of bolts 57
located between the flanges of the profiles 59 bear on the hard rubber
layer 60 coating the flanges of the rolled profile 59 located near the
belt 27. The profile 58 may also be employed in the preceding embodiments.
In the embodiment shown in FIG. 13 for an endless track suitable for use on
a row of single wheels or on a row of double wheels, the surface of the
flexible belt 27 remote from the wheels is provided with a profile 61
having essentially an I-shaped cross-section and being made from a
synthetic resin or a kind of rubber preferably provided with liners. The
flange of each profile 61 facing the flexible belt 27 is embedded in a
gutter-shaped rolled-steel profile 62 comprising the boundary face of the
flange of the profile 61 facing the belt 27 as well as the two sides of
said flange, the profile 62 being secured by vulcanization to the
synthetic plastics or rubber profile 61.
In the embodiment shown in FIG. 14, the surface of the belt 27 remote from
the wheels is provided with a profile 63 also of synthetic resin or a
rubberlike material, the profile again having essentially an I-shaped
cross-section. As in the preceding embodiment the profile 62 is directly
secured to the belt 27 by two rows of bolts 64. The outer boundary face of
the flange remote from the belt 27 is, in this embodiment, slightly convex
as is shown in FIG. 14.
When the vehicle driver energizes the two hydraulic cylinders 21 so that
the front axles 23 move towards the pivotal shafts 20, the arms 18 thus
being turned about the pivotal shafts 17, the distance between the front
axle and the further wheel axles 5, 8 is reduced so that the caterpillar
track 26 can be passed manually around the three sets of wheels without
the need for further means. It may be advisable in this case to provide
each endless tread track with one or more joints which are closed after
the belt has been arranged around the wheels. Subsequently, the hydraullic
cylinders 21 are again energized so that the lower ends of the arms 18
turn forwardly to tension tracks 26. During operation, the pressure in the
hydraulic cylinders 21 is maintained at a predetermined value in known
manner.
The rear wheels 7 are driven by the engine 2 through the gear box 3, the
auxiliary shaft 4 and the differential 6 while the lower run of each track
26 moves, with respect to the frame 1, in a direction opposite the
direction of forward travel A. The central wheels 9 and the front wheels
24 will then rotate freely. When the lower part of one of the endless
tracks runs across local unevennesses, so that this part of the track is
displaced upwardly between two sets of the wheels, the front axle 23 can
move resiliently towards the pivotal shaft 20 if the hydraulic system of
the cylinders 21 includes a pressure accumulator so that the tension of
track 26 cannot reach an undesirably high value. The moment exerted by the
rear wheels 7 on track 26 is transmitted by the extensions 29 with the
rubber coating 30, which are jammed between the neighbouring sides of the
pairs of tires and penetrate to some extent into the tire treads and by
the grip of the tread of the curved outer surface of each tire on a large
number of the strips 28, which are then in contact with the tires of the
rear wheels 7. The distances between two adjacent strips 28 and the
associated extensions 29 are, of course, chosen so that the number of
strips and extensions constantly in contact with the rear wheels 7 is
sufficiently large for transmitting the required tractive moment to tracks
26. For negotiating bends, a set of rear wheels on one side of the tractor
is not driven or is blocked in known manner, whereas the set of rear
wheels 7 on the other side of the tractor is driven. In order to be able
to reduce, if desired, the surface contact of one of the caterpillar
tracks when driving through a bend, one of the hydraulic cylinders 15 is
energized so that the arm 16 is turned upwards with respect to the frame 1
as a result of which one of the front wheels 24 is lifted from the ground.
The tension of track 26 is maintained by preserving the pressure in the
corresponding cylinder 21 in known manner at a constant value or by means
of a pressure accumulator. By simultaneous energization of the two
cylinders 15, the two front wheels 24 can both be moved upwards or
downwards with respect to the further part of the vehicle owing to the
angular displacement of the arms 16, if the inclination of the field to be
covered abruptly varies, for example, at the edge of a slope.
The hydraulic system communicating with the two cylinders 15 may also
include a pressure accumulator in order to dispose the front axles in a
resilient or flexible manner having regard to the tension of tracks 26.
In the embodiments shown in FIGS. 3 and 4; in which its row of extensions
29 fixes each track 26 in a lateral direction with respect to the wheels
the flange of one of the two profiles 32 in each profile 31 extending
rearwardly of the direction A and forwardly in the direction of rotation
of the lower run of track 26 with respect to the frame is urged rearwardly
into the soil owing to the driving moment. Since the flange of the
rearmost profile 32 located at a distance beneath the flexible belt 27 and
extending in said direction is exposed to a forwardly directed force, a
moment is exerted on the flexible belt 27 which is such that the whole
profile 31 tilts slightly. In FIG. 3 the angle of downward tilt relative
to the ground is about five degrees.
As a result, the grip of each profile 31 on the soil is materially enhanced
owing to the resultant resistance of the profile. The flexible belt 27
will then assume the position shown diagrammatically in FIG. 3. Thus,
also, the grip of the strips 28 and of the extensions 29 on the tires is
increased. This phenomenon occurs similarly in all of the other
embodiments. Owing to the deformation of the belt 27, the neighboring
flanges 37 of two adjacent profiles 34 (FIG. 5) will turn relative to one
another so that these flanges produce a sawtooth-like formation which
increases the grip on the ground. In the embodiment shown in FIG. 6, the
profiles are secured, in contrast to the other embodiments, by only one
row of the bolts 33 so that a comparatively large tilting movement due to
the tractive force can occur resulting in a comparatively strong grip on
the ground. In the embodiments of FIGS. 7 and 8, apart from said tilting,
a larger ground surface contact is obtained by the relatively broad
flanges 42 and 47. The eccentric disposition of the flange 42 (FIG. 7)
with respect to the contact surface on the belt 27 can increase the
tilting movement initiated by the tractive force. In the construction
shown in FIG. 8, the two flanges 47 of the profile 44 will both tilt in
the event of a high tractive force so that the grip on the ground is
appreciably enhanced. The flat bottoms of the profiles in the preceding
embodiments ensure a low contact pressure when the profiles have not
tilted, which will be the case when a low tractive force is sufficient,
for example, on bituminous roads, while damage to such roads is avoided.
In the embodiments of FIGS. 9 and 10, the partitions 53 prevent lateral
emergence of soft or other weak soil from the profiles 49 when the latter
have tilted and have penetrated into the ground in a scooping position.
The convex outer surfaces of the flanges 52 are conductive to the tilting
movement of the profiles when contacting the ground and produce a further
tilting when the driven wheel approaches the profile 49. The profiles 58
of the embodiment of FIGS. 11 and 12 have a similar effect to those of the
preceding embodiments. However, the envelopment of the rolled profiles 59
in the flexible material layer 60 improves on the one hand, the flexible
joint between the profile 59 and the belt 27 and reduces on the other
hand, the risk of damage to the road surfaces on bituminous roads. The
curved bottom of the flexible envelope layer 60 improves, on the one hand,
the tilting movement of the profile when a high tractive force is exerted,
and ensures, on the other hand, a low contact pressure on asphalt roads
with a low tractive force, since the flexible material layer 60 will
deform so that a flat bottom side of the flexible envelope will
effectively be formed. This also applies to the embodiment of FIG. 14, in
which the whole profile 63 consists of flexible material so that a broad
contact surface is obtained on hard roads. A similar effect is obtained by
the profile 61 of FIG. 13 which consists entirely of flexible material and
which already has a flat bottom, the profile 62 preventing an excessive
deformation of the profile 61 near the belt 27 so that the fit of the bolt
joint is maintained under all conditions.
It should be noted that the vehicle shown in FIGS. 1 and 2 may, of course,
also be used without the tracks 26. In both cases an advantageous
distribution of the weight of the driving engine 2, of the gear box 3 and
that of the implement or tool to be attached to the lift 25 among the
three sets of wheels 7, 9, 24 is obtained so that a uniform distribution
of the surface pressure among the three sets of wheels and along the
length of tracks 26 with the ground is ensured.
In a further embodiment the vehicle shown in FIG. 15 comprises a frame 101
having two substantially horizontal and relatively parallel frame beams
102, the frame 101 being supported by steerable front wheels 103 and by
two pairs of rear wheels 104 and 105 arranged one behind the other on
either side of the vehicle. The two foremost rear wheels 104 and the
hindmost rear wheels 105 are in line behind the former considered in the
direction A and are provided with tires 106 having conventional profiles.
The front wheels 103 are also provided with tires. The diameter of the
foremost rear wheels 104 is substantially equal to that of the hindmost
rear wheels 105. In this embodiment, the diameter of the front wheels 103
is equal to that of the rear wheels 104 and 105 but the diameter of the
front wheels 103 may be larger or smaller than that of the rear wheels.
Axles 107 of the front wheels 103 are fastened through steerable pivot
pins or king pins 108 to a front axle beam 109 extending perpendicular to
the direction A, the beam 109 being freely pivotable in a vertical plane
of substantial symmetry of the tractor on a horizontal pivot shaft 110
extending in the direction A, and being journalled in a support fastened
to a transverse beam 111 which interconnects the front ends of the
longitudinal frame beams 102. Viewed from one side (FIG. 15) the pivotal
shaft 110 is located substantially midway between the top and bottom of
the transverse beam 111. Wheel axles 112 of the foremost rear wheels 104
and wheel axles 113 of the hindmost rear wheels 105 are supported on one
side of the tractor, in a beam 114 extending parallel to the direction A
and being located alongside the corresponding frame beam 102. The
supporting beam 114 is freely pivotable about a shaft 115 which extends
horizontally perpendicular to the direction A and which is located beneath
the bottoms of the frame beams 102. The two supporting beams 114, together
with the rear wheels coupled thereto, are freely pivotable about the shaft
115. The pivotal shaft 115 is located on one side of the aforementioned
vertical plane of substantial symmetry between the wheel axles 112 and
113, that is to say, between said plane and the corresponding wheel axle
113. The foremost rear wheels 104 are freely rotatable on the axles 112.
The two wheel axles 113 are extended in the space between the two
supporting beams 114 and are coupled together by a differential gear 116
which has an upwardly extending input shaft coupled with the output shaft
of a torque converter 117, the latter being pivotable to a limited extent
relative to the frame 101 of the tractor and being connected to said
frame. The torque converter 117 is located, viewed in side elevation
wholly or partly above the hindmost rear wheels 105. The connection
between the output shaft of the torque converter 117 and the input shaft
of the differential 116 is telescopic in view of potential movements of
the supporting beams 114. The torque converter 117 may comprise two pairs
of adjustable wheel discs, said pairs being interconnected by a chain so
that, by relative adjustment of each of the pairs of wheel discs, a
continuously variable transmission can be obtained. The torque converter
117 comprises an input shaft which can be driven through an auxiliary
shaft 118 by the tractor engine 119, the auxiliary shaft 118 preferably
being telescopic and being provided with two universal joints 120 so that
relative movements of the torque converter 117 and the tractor engine 119
are possible.
The front wheels 103 are steerable from a driver seat 121, which is
located, as seen in FIG. 15 at a distance above the top points of the rear
wheels 104 and 105 and, viewed in plan (FIG. 16) in the position shown in
FIG. 15 between the wheel axles 112 and 113. The driver seat 121 is
fastened to a console 122, to which is fastened, moreover, a column 123
provided with a steering wheel 124 and all further steering and
control-members. The assembly of the seat 121, the console 122, the column
123, the steering wheel 124 and all further steering and control-members
is pivotable as a whole about a substantially vertical pivotal shaft 125
located in the vertical plane of substantial symmetry of the tractor. The
assembly can be fixed in the positions differing by 180.degree. around the
axis of said shaft 125 so that the front of the seat 121 faces in the
direction of forward travel A or in the opposite direction. The driver
seat 121 is surrounded by a cabin 126 extending, as seen in FIG. 15 above
the rear wheels 104 and 105.
The rear of the tractor shown in FIG. 15 has a threepoint lift 127 which
can be hydraulically energized from the driver seat 121. Viewed in FIG. 15
those parts of the two frame beams 102 which are located between the rear
regions of the front wheels 103 and the front regions of the rear wheels
104 are provided on either side of the tractor with a lifting device 128,
the lower lifting arms 129 of which are connected to the bottoms of the
frame beams 102 so as to be pivotable about horizontal shafts 130
extending in the direction A by hydraulic agency from the driver seat 121.
The top arm 129A of the lift 128 bears on the top of the adjacent frame
beam 102.
A front three-point lift 131 comprises lower lifting arms 132 and a top
lifting arm 133 arranged to pivot about substantially horizontal shafts
134 and 135 respectively, said shafts extending perpendicular to the
direction A and being journalled in a support 136 located at a small
distance in front of the front axle beam 109. The lifting device 131 can
also be actuated from the driver seat 121 by a hydraulic agency. The
support 136 is fastened in position by two arms 137 extending away from
the support 136 to the rear. Each of the arms 137 is located, as seen in
FIG. 15, at a small distance above the top of the adjacent frame beam 102
and, as seen in FIG. 16, on the outer side of the corresponding frame beam
102. Near the rearmost ends of the arms 137, which are located, viewed in
plan, about midway across the space between the wheel axles 107 and 112,
said arms are provided with fastening lugs 138 holding horizontal pivotal
shafts 139 extending perpendicular to the direction A. Each of the pivotal
shafts 139 is fastened to the side of the adjacent frame beam 102. The
joint between each pivotal shaft 139 and the associated lug 138 is
preferably movable, for example, by means of a ball hinge arranged in a
comparatively large rubber support socket in the lug 138. At a short
distance behind the support 136, the bottom of each arm 137 bears on the
top of the front axle beam 109, and, between the bottom of each arm 137
and the top of the front axle beam 109, there may be arranged a rubber
support 140. An undesirable upward displacement of either arm 137 with
respect to the front axle beam 109 is prevented by a stop (not shown)
formed, for example, by a bolt passed vertically through the arm 137 and
fastened in the front axle beam 109, said bolt having a stop plate bearing
on the top of the arm 137. In this way the lift 131 can follow the
movements of the front axle beam 109 so that a machine or a total attached
to the lift 131 can match the unevennesses of the ground independently of
the movements of the tractor frame 101. The tractor frame 101 generally
follows the movements of the rear wheels which are located, however, at a
relatively large distance behind the machine or tool attached to the
foremost lift 131. The disposition of the lift 131 is, therefore,
preferably such that the machine or tool attached to said lift is located
at a relatively short distance from the front wheels 103. Since the front
of the tractor frame has, in general, a light construction, this front is
advantageously hardly loaded by the lift 131 because the lift directly
bears on the front axle beam 109 and otherwise at a place on the tractor
frame 101 located at a distance behind the front wheels 103, while the
pivotal shafts 139 exert, in general, upwardly extending forces on the
frame beams 102. Therefore, the lift 131 and its connections may be the
same as are provided on standard tractors.
Near each lifting device 128, a power take-off shaft 141 extends
substantially horizontally perpendicular to the direction A and is driven
at the engine speed. Near the rear lift 127, and also near the front lift
131, further power take-off shafts 142 and 143 are provided.
From FIGS. 17 and 18 it will be apparent that the pairs of rear wheels 104
and 105 on either side of the tractor are surrounded by an endless tread
track 144 passing around the treads of the tires 106 of the two pairs of
wheels 104 and 105. Each track 144 comprises an endless belt 145, the
width of which corresponds substantially with the width of the adjacent
wheels 104 or 105. Each belt 145 is provided on the inner surface facing
the wheels 104 and 105 with a large number of equidistant teeth or cams
146 in a row parallel to the direction of length of the belt 145.
Considered in the direction of length of each belt (FIG. 18) each tooth or
cam 146 is disposed symmetrically to a vertical plane of symmetry of that
belt 145. Each tooth or cam 146 has the shape of a truncated pyramid, the
side faces of which converge away from the belt 145. Considered in the
direction of length of the belt 145 (FIG. 18) the dimensions of each cam
146 are such that it fits between the side faces adjacent the treads of
the two tires 106 on either side of the cam. A cam 146 engaging the wheels
104 and 105 is thus located between the outer parts of two neighboring
tires and its shape is such that it is firmly in contact with the profiles
at the sides of the tires. This contact pressure is such that, in the case
of a driven wheel, the tires can entrain the teeth or cams and hence the
further parts of each caterpillar track.
On the outer surface that is remote from the wheels 104 and 105, each belt
145 is provided with a large number of transverse ridges 147 covering its
whole width. Each ridge 147 is preferably located directly opposite a
tooth or cam 146 on the other side of the belt 145. Each ridge 147 is
provided at a distance from the belt 145 with a supporting part 148 having
a flat outer surface, which comes into contact with the ground and which
has essentially the shape of a parallelepiped. The supporting part 148 of
each ridge 147 is connected by a tie part 149 with the belt 145. As seen
in FIG. 17, each tie piece 149 is narrower than the corresponding
supporting part 148 and terminates in the supporting part 148 through a
cavity 150. The cavity 150 covers the whole width of each transverse ridge
147. The cavity 150 is orientated to the front with respect to the
direction of rotation of track 144 (direction B in FIG. 17) so that the
ridge 147 forms a scoop-like member on that side. On the side of the tie
piece 149 located opposite the cavity 150, a further cavity is provided in
this embodiment as a mirror image of the cavity 150. This rear cavity, in
the direction B, provides, in the disposition shown, an increased
flexibility of the supporting part 148 with respect to the belt 145 and
said cavity has the same function as the cavity 150 when track 144 is
applied to the wheels in a reversed position or when the tractor travels
rearwardly. FIG. 18 shows that the belt 145 is provided with a liner
comprising a large number of coplanar, parallel steel wires 151 extending
parallel to the direction of length of track 144, said wires being endless
on a circular path. These steel wires 151 are interconnected by a large
number of steel wires 152 extending parallel to one another in the
direction of width of track 144. The steel wires 152 are preferably
fastened to the steel wires 151 crossing the same at right angles so that
a network is formed. Instead of using steel wires, strong synthetic
plastics or other fibers may be employed. The network of steel wires 151
and 152 is embedded in the material of the belt 145. The belt 145, the
teeth or cams 146 and the transverse ridges 147 are integral and made from
a single piece of flexible material, for example, a synthetic resin or a
rubber-like material.
During operation, the tractor engine 119 drives only the axles 113 of the
hindmost rearwheels 105 through the auxiliary shaft 118, the variable
torque converter 117 and the differential 116. With a direction of
rotation of the rearwheels 105 corresponding with the direction A, the
driving moment of each wheel axle 113 is transmitted through a wheel disc
153 (FIG. 18) to a wheel flange 154 holding wheel rims 155 of the tires
106. Upon rotation, the tires 106 carry along the teeth or cams 146
located between them so that each track 144 is rotated. The foremost rear
wheels 104 are driven solely by tracks 144. The tractive run of each track
144 is located on the ground and is vigorously drawn rearwardly by the
driving moment of the hindmost rear wheel 105 (direction B) so that parts
of track 144 deform as is shown in FIG. 17. The reaction force exerted by
the ground on the supporting parts 148 curves the belt 145 so that the
supporting parts 148 tilt to some extent and the cavities 150 grip into
the ground, thus providing a very high resistance to slipping and
skidding.
It has been found that the grip of the tires 106 on the sandwiched cams
146, when the tractive part of each track 144 is in contact with the
ground, is appreciably higher than in the case in which the tractive part
of track 144 is not in contact with the ground. This is the case, for
example, when the rear wheels 105 are driven so that the tractor travels
in reverse. This increased clamping of the teeth or cams 146 between the
tyres 106 depends upon the resistance experienced by the tractive part of
track 144 on the ground, which resistance is appreciably influenced by the
aforesaid tilting movement of the supporting parts 148. A similar endless
tread track structure may also be used when, on | | |
