Note: Descriptions are shown in the official language in which they were submitted.
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SUSPENSION FOR OPERATOR~S PLATFORM
Background of the Invention
Field of the Invention
The invention concerns a suspension system for the
operator's platform of agricultural or industrial vehicles.
Description of the Related Art
On slow-moving vehicles such as agricultural tractors and
the like, the operator's platform on which an operator's cab
or a four-column roll-over structure may be mounted usually is
r.ot supported on springs, but is attached with bumpers or
rubber mounts to the vehicle body. Due to their small spring
deflection, these mounts provide isolation of structure-borne
noise, but do not provide significant elastic support for the
operator's platform. Low-frequency mechanical vibrations
generated by operation over rough terrain can be transmitted
right through them to the attachment point of the operator's
seat, without any damping. To assure at least a certain
degree of comfort for the operator, the vertical, horizontal,
transverse and pitch vibrations typically are absorbed by
spring-mounting the operator's seat.
For ergonomic reasons, the spring support of the
operator's seat should not be too soft, since this would
increase the spring deflections and lead to comparatively
large relative motion between the operating controls and the
operator. If this happened during shock loads, the operator
might lose contact with the operating controls and adjusting
levers mounted on the operator's platform. Unfortunately,
these limitations on vibration isolation lead to a spring
support for the seat whose resonant frequency may lie in the
range of natural frequencies of several internal human organs,
which is perceived as being uncomfortable. The spring support
of the seat also does not prevent transmission of vibrations
through operating controls mounted on the operator's platform.
EP-Bl-0 273 796 describes an elastic support for the cab
of an agricultural tractor, in which MacPherson struts are
provided to absorb vibrations between a stiff chassis on the
- one hand and transverse structures connected to the cab on the
other. This elastic support permits pitch vibrations about
the transverse axis that give the operator an impression of
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tumb:Ling motion, which may impair his control of the vehicle.
The lcnown arrangement requires a multitude of Panhard rods to
absorb horizontal forces and is relatively costly.
Furthermore, tuning of the elastic supports is difficult.
SummarY of the Invention
The object of the present invention is to provide a
suspension for an operator's platform that largely decouples
the operator's platform from vibrations of the vehicle chassis
while avoiding the difficulties noted above. The vibrations
in the vertical longitudinal plane of the vehicle, in
particular, are to be isolated by elastic supportæ while
transverse forces are absorbed with relatively high stiffness.
This object is achieved according to the invention by
mounting the operator's platform with several longitudinal
links. Generally horizontal torsion bars, oriented transverse
to the direction of travel, then are clamped fixed against
rotation between the operator's platform and the first end of
each longitudinal link. The clamping is performed by fixed
bearings. In particular cases the fixed bearings may
appropriately be replaced by shock mount bearings. The second
end of each longitudinal link is pivotally mounted to the
vehicle chassis with its pivot axis oriented parallel to the
torsion bar. The longitudinal links can be attached through a
mount or the like, for example, to a vehicle frame, a gearbox
housing or an axle housing. The torsion bar, clamped at both
ends, is stiff against torsion and bending forces and is
loaded in torsion.
This application of longitudinal links limits the number
of degrees of freedom of the operator's platform to a plane of
motion oriented vertically in the longitudinal axis of the
tractor. Depending on the angular position of the links,
vertical and horizontal pitching vibrations, as well as
pitching vibrations oriented in the direction of travel, can
be absorbed. Isolation of the transverse vibrations is
largely omitted in view of their aforementioned disadvantages.
Supplementary measures may be taken against vibrations in
the lateral direction, that is, for transverse vibrations. In
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addition to supporting the operator's platform with bumpers,
horizontal and lateral seat support springs are appropriate.
The introduction of such additional degrees of freedom
preferably is consciously limited to assure that sufficient
motion from the vehicle reaches the operator for the operator
to recognize the vehicle's operating behavior and to avoid
kinesia (motion sickness or seasickness), which is traced
primarily to transverse and roll vibrations.
A symmetrical support of the operator's platform is
provided most appropriately by an equal number of longitudinal
links pivotally connected on both sides of the operator's
platform, each of which carries an associated torsion bar.
The torsion bars are arranged parallel to each other. Torsion
bars associated with two longitudinal links located generally
opposite each other are aligned with each other or are at
least located close to each other in space.
Preferably, each longitudinal side of the operator's
platform is provided with a forward and a rear longitudinal
link each of which carries a torsion bar. For the support of
heavier operator's platforms with a superstructure, more than
four longitudinal links with the associated torsion bars may
also be appropriate.
The instant center of vibration is found at the
intersection of the extension of the axes of the front and the
rear links, and represents a virtual pivot point for the
operator's platform. When the longitudinal links are
parallel, of equal length and located one behind the other,
the instant center is located at infinity. The result is that
of an infinitely long pendulum. This arrangement forces the
tractor cab essentially into the motion of a parallelogram
sus~ension.
By orienting longitudinal links situated behind each
other so as not to be parallel and/or by the application of
longitudinal links of different lengths, the instant center
can be positioned at a finite location. It can be oriented
about the horizontal plane of the center of gravity of the
operator's platform, if necessary including the cab
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superstructure, which results in relatively neutral behavior
under horizontal inertial forces that occur during braking and
acceleration. The application of longitudinal links of
different lengths leads to a superposition of translational
and pitch vibrations, moving the position of the instant
center from its rest position.
Preferably the direction of the longitudinal l mk, more
precisely, the line connecting the clamping point of the
torsion bar and the pivot axis, is at an angle between 0 and
30 to the horizontal. The static spring deflection is
determined by the position assumed at rest without any dynamic
effects. The angle at which the longitudinal links are
inclined upward or downward and the selection of the forward
or rear end of the longitudinal links for the connection to
the pivot on the vehicle chassis depends on the total
requirements.
When the longitudinal links are flat, the operator's
platform moves almost exclusively in the vertical direction
under the effect of vibrations, while with longitudinal links
other than horizontal the vertical motion is superimposed on a
motion in the longitudinal direction of the vehicle.
According to a preferred embodiment of the invention, the
axis of the torsion bar is supported in the vicinity of its
clamping point on the longitudinal link in a bearing on the
operator's platform that permits rotation of the torsion bar.
This bearing supports the torsion bar on the operator's
platform. The hearing may be a sliding bearing.
The arrangement of the torsion bars may follow several
preferred principles in which the operator's platform is
provided with two frame members at the sides oriented in the
direction of travel, and the bearings supporting the torsion
bars are each located in one of the side frame members.
According to a first arrangement, the end of each torsion
bar is fixed against rotation to the side frame member which
is opposite the side frame member at which its bearing and its
associated longitudinal link are arranged. Here the torsion
bars are arranged close together, one pair behind the other.
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In a second arrangement, the ends of each torsion bar are
clamped in two longitudinal links on opposite sides of the
operator's platform, and are supported in the side frame
members of the operator's platform. The middle of the torsion
bar t:hen is clamped in a center frame member of the operator's
platform. Alternatively, in place of the long one-piece
torsion bar clamped in the center, two shorter separ~te
torsion bars could be employed that are clamped to the center
frame membex.
A further arrangement has each torsion bar extend through
an associated torsion tube, with the torsion tube clamped at
its one end to the frame member and at its other end to the
torsion bar. The torsion bar and the torsion tube are
concentric to each other and are supported at the center of
the operator's platform. The end of the torsion bar extending
to the side from the end of the torsion tube is clamped to the
associated longitudinal link. The spring rates of the torsion
bar and the torsion tube are arranged in series. The total
spring characteristic may be modified over a wide range by the
design of each spring component.
If transverse or rolling motions are to be freed, then
degrees of freedom in the transverse direction must be
- permitted. To absorb the resulting transverse forces,
preferably a further torsion bar is provided directed
generally horizontally and transverse to the direction of
travel and rigidly clamped between the first ends of two
longitudinal links arranged on opposite sides of the
operator's platform. Each of the second ends of the
longitudinal links can pivot about an axis in the vehicle
chassis parallel to the axis of the torsion bar. Furthermore
the axis of the torsion bar is supported in bearings on the
operator's platform in the vicinity of each of the two
longitudinal links.
By means of this connection of two longitudinal links
located on the transverse opposite sides of the direction of
travel through a torsion bar supported on the operator's
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platEorm, transverse forces can be absorbed elastically. This
results in a stabilizing effect.
Furthermore there is an advantage in providing a Panhard
rod extending generally transverse to the direction of travel
that is arranged between the operator's platform and the
vehicle chassis. The Panhard rod is loaded only by tensile
and compression forces. Preferably it is located in the plane
of the center of gravity under the operator's platform and
absorbs transverse loads during rolling motions, so as to
avoid a lateral excursion of the operator's platform.
The free bearing between the longitudinal link and the
vehicle chassis performs a support function and permits
pivoting of the longitudinal link with respect to the vehicle
chassis. Rubber-metal isolators preferably are applied to
absorb structure-borne noise. Preferably such silencing
devices are provided at the lower attaching point of the
longitudinal links on the chassis side. The rubber bearing
can be tuned for a guided although small lateral deflection to
absorb transverse forces elastically.
The stiffness of the silencing devices should be selected
with respect to its pivot axis in the axial and radial
directions depending on their configuration. For this purpose
an integrated solution is preferably used with rubber guides
vulcanized onto the longitudinal links or a link bearing with
flange blocks clamped against each other.
To limit the relative motion between the operator's
platform and the vehicle chassis, end stops are preferably
provided, for example, rubber or elastomeric bumpers. The end
stops may be attached to the longitudinal links. The bumper
action can be enhanced by utilizing the lever ratios of the
longitudinal links. With their help a progressive spring
characteristic can be attained over a larger area.
Dampers are preferably arranged between the operator's
platform and the vehicle chassis, located to each side of the
operator's platform in the plane of its center of gravity.
The dampers may appropriately be shock absorbers common in
motor vehicle practice. The restrained kinematic guidance of
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the longitudinal links permits a reduction in the nu~ber of
dampers in comparison to conventional operator's platform
suspensions.
The rigid clamp connections between the torsion bars and
the operator's platform or the longitudinal links are
prèferably designed so that they can be unclamped. After
releasing the clamps, the operator's platform may be raised by
pivoting the longitudinal links pivot to their zenith. The
raised operator's platform permits access to vehicle
components located underneath and makes service operations
easier. For reasons of safety, before operations are
performed under the operator's platform it should be secured
against undesired lowering.
The operator's platform may be raised by a vehicle jack
or other means. For this purpose a power source may be used
that is already available on the vehicle whose power is
transmitted by a transmission linkage or the like to the
operator's platform.
Brief Description of the Drawings
The invention will be described further with reference to
the following drawings, in which:
Fig. 1 is a schematic side view of a suspension according to
the invention of an operator's cab on the chassis of an
agricultural tractor.
Figs. 2 through 5 show several variations of the torsion bar
arrangements of a suspension according to the invention.
Figs. 6 through 8 are cross sectional views of several
variations of the pivot bearing of a suspension according
to the invention.
Fig. 9 illustrates the arrangement of a Panhard rod used with
a suspension according to the invention.
Fig. 10 is a schematic side view of an agricultural tractor
with the cab raised.
Figure 11 shows a lifting arrangement for the cab.
Detailed Description of the Preferred Embodiments
Fig. 1 schematically illustrates the rear wheel 11 of a
vehicle that carries an agricultural tractor substructure,
designated vehicle chassis 14. Above the vehicle chassis 14
there is an operator's platform 12 upon which a cab 10 is
mounted. The vehicle chassis 14 and the operator's platform
12 are connected by front and rear longitudinal links 36, 38
and dampers 13 arranged on each side of the cab. Furthermore
Fig. 1 indicates the position of a Panhard rod 130 which lies,
along with the dampers 13, in a vertical plane transverse to
the direction of travel and that includes the center of
gravity S of the cab 10.
The front longitudinal links 36 can be supported through
mounts 45 on the vehicle chassis or a gearbox housing, and the
rear longitudinal links 38 can be supported through mounts 47
on the axle housings 49 of the agricultural tractor. On the ;
sides O:e the front mounts alongside the extended second ends
42 of the front longitudinal links 36, rubber blocks 51 are
attached which are used as stops and limit the pivoting path
of the front longitudinal links 36.
The floor structure of the operator's platform 12 is
indicated in plan view in Figs. 2 through 5, in which
corresponding components are designated by the same part
number call-outs. It forms a frame structure and generally
includes four tube-shaped supports arranged at right angles to
each other, that is, two side frame members 16, 18, a front
frame member 20 and a rear frame member 22. The side frame
members 16, 18 are perforated with holes. Bearings 24 are
inserted into the holes and accept torsion bars 26, 28, 30, 32
(see Figs. 2, 3, 4, 5, respectively). The bearings 24, not
shown in greater detail, support the torsion bars 26, 28, 30,
32 relative to the operator's platform 12, but permit rotation
of the torsion bars 26, 28, 30, 32.
The end of each torsion bar 26, 28, 30, 32 projecting
outward beyond the bearing 24 is clamped by fixed bearings to
prevent rotation or by other means in the corresponding first
end 34 of each longitudinal link 36, 38, which is rigid
against torsional and bending forces. An isolating bearing
can be employed in particular cases in place of the fixed
bearing 40. The other, second end 42 of each longitudinal
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link 36, 38 is connected through a free bearing in mounts 45,
47. The free bearing (discussed in detail in connection with
Figs. 6-8 below) permits pivoting of the longitudinal links
36, 38 about a pivot axis 44 oriented parallel to the axis of
the torsion bars.
The ends of the torsion bars 26, 28, 30, 32 opposite the
ends clamped in the fixed bearing 40 of the longitudinal links
36, 38 are attached by differing means, as shown in each of
Figs. 2 through 5.
In the embodiment of Fig. 2, the other end of each
torsion bar 26 is clamped in the corresponding opposite side
frame member 16, 18 by a fixed bearing 46. In this variant
four torsion bars 26 are used, with the two front bars and two
rear bars located ; -~iately adjacent to each other.
The embodiment of Fig. 3 uses only a single front and a
single rear torsion bar 28. Each torsion bar 28 is clamped at
both its ends in a fixed bearing 40 in the longitudinal links
36, 38 arranged on the outside of the side frame members 16,
18 and is supported in the bearings 24 in the side frame
members 16, 18. The center region of each torsion bar 28 is
clamped, fixed against rotation, in a fixed bearing 48 to a
center frame member 50. Alternatively, each torsion bar 28
can be formed of two partial bars that are aligned with each
other and are clamped in the center frame member 50.
The embodiment of Fig. 4 uses two torsion tubes 52. Each
tube is attached to side frame members 16, 18 by rigid
connections 54 and extends into the interior of the frame.
The free ends of the torsion tubes 52, directed toward the
interior of the frame, are supported, free to rotate, in a
center frame member 50. A torsion bar 30 extends
concentrically within each torsion tube 52 and is clamped at
its one end by a rigid connection 40 in the longitudinal links
36, 38 and at is other end is clamped, fixed against rotation,
to the free end of the associated torsion tube 52.
The embodiment of Fig. 5 uses a first, front torsion bar
28 clamped, fixed against rotation, as are the torsion bars 28
in Fig. 3, between the two outer longitudinal links 36 and a
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center frame member 50, while a second, rear torsion bar 32 is
clamped only between the two outer longitudinal links 38. The
first torsion bar 28 absorbs vertical forces. The second
torsion bar 32 has a stabilizing effect and absorbs roll
motions. The second torsion bar 32 may also be used in
combination with one or more of the torsion ~ar arrangements
shown in Figs. 2 through 4.
In operation, motion will cause the longitudinal links `
36, 38 to rotate about their pivot axes 44, producing an up
and down movement of the operator's platform 12 with the
attached operator's cab 10. This applies torsion to the
torsion bars 26, 28, 30, 32 and the torsion tubes 52, if
applicable, resulting in elastic support of the cab 10. In
addition, if the operator's platform 12 is tilted to the side,
the two rear longitudinal links 38 of Fig. 5 deflect to
differing degrees against the force of the torsion bar 32.
The torsional force in that embodiment therefore also provides
a restoring force against sideways tilting.
Figs. 6 through 8 illustrate various embodiments of the
mounts 45, 47.
Fig. 6 shows an L-shaped mount 60 which can be fastened
to the vehicle frame or gearbox housing (not shown) by bolts
62 (of which only the centerlines are shown). A leg 61
extending vertically upward from the mount 60 has pivot pin 64
welded thereto. The pivot pin 64 carries two bearing washers
66, 68 and an intervening sleeve 69 which are clamped by a pin
70 against a side face 71 of the vertical leg 61. The outer
surface of the sleeve 69 engages a rubber grommet 72 that is
vulcanized to the longitudinal link 36, 38 and which can pivot
between the bearing washers 66, 68 about the pin 64. The
bearing support shown in Fig. 6 permits pivoting of the
longitudinal links 36, 38 and can limited absorb roll
vibrations between the vehicle chassis 14 and the operator's
platform 12.
Fig. 7 shows a different variant for the bearing support.
Here a T-shaped mount 74 can be fastened to the vehicle
chassis 14 with bolts 62. The central leg 76, extending
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vertically upward from the mount 74, is provided with a bore
that engages an elastic sleeve 78. Rubber flanges 80, 82 are
arranged on each side of the sleeve 78. Each rubber flange
80, ~2 carries a leg 84, 86 of a longitudinal link 36, 38
conf:igured in two spans. A pin 88 extends through bores in
the sleeve 78 and the rubber flanges 80, 82 and is provided on
one side with a welded washer 90. The sleeve 78 and the
rubber flanges 80, 82 are clamped by a pin 92 with a plain
washer 94 between the welded washer 90 and a further washer
96. This bearing support also permits pivoting of the
longitudinal link and absorbs limited roll vibrations.
The variant shown in Fig. 8 provides a U-shaped mount 100
with legs 102, 104 extending upward and provided with bores to
engage a transverse pin 106. A washer 108 is welded to one
end of the transverse pin 106. A bolt 110 is fastened at the
end of the transverse pin 106 opposite the washer 108, and,
together with a washer 112, clamps the two legs 102, 104
between the welded washer 108 and the washer ~12. Bearing
washers 114, 116, 118, 120 are arranged on each side of each
leg 102, 104. Two elastic flange blocks 122, 124 are clamped
between the center bearing washers 116, 118. A longitudinal
link 36, 38 is clamped between and supported by the flange
blocks 122, 124. The bearing washers 114, 116, 118, 120
reduce the friction of the longitudinal link 36, 38 pivoting
about the pin 106. The bearing support according to Fig. 8
exhibits a high transmissibility for forces in the
longitudinal direction of the links and a low transverse
elasticity.
During roll movement, transverse forces can be absorbed
by a Panhard rod 130 which is loaded only by tensile and
compression forces. The arrangement of the Panhard rod 130 is
shown in Fig. 9, which represents a schematic partial view of
the vehicle from the rear. A front longitudinal link 36 is
provided on each side of the operator's platform 12, which
carries the cab 10. As a result of the applied transverse
forces the two longitudinal links 36 are deflected to
differing degrees, so that they appear to have differing
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lengths when viewed from the rear. One end of the Panhard rod
130 is pivotally connected at one side of the operator's
platform 12. Its other end is pivotally connected to the
opposite side of the vehicle through a mount 131 to the
vehicle chassis 14. The result is limitation of sideways
movement in either direction.
If the clamps 40 that hold the torsion bars 26, 28, 30,
32 in the longitudinal links 36, 38 or the clamps 46, 48
between the torsion bars 26, 28, 30, 32 and the side or center
frame members 16, 18, 50 are released, then the longitudinal
links 36, 38 can be rotated about their pivot axes 42 and
erected upward without applying any torsional loads to the
torsion bars 26, 28, 30, 32 or, if applicable, to the torsion
tubes 52. The operator's platform then can be raised to
provide access to vehicle components located underneath the
operator's platform 12.
The longitudinal links 36, 3~ are shown erected
vertically in Fig. 10. Rotation of the four longitudinal
links 36, 38 and the raising of the operator's platform 12 can
be performed through a linkage 140 by the remotely-controlled
lifting arms 143 of a front hitch or other lifting arrangement
142 at the forward end of the vehicle, or lifting arrangement
148 actuated by a rear hitch or other lifting arrangement 144
with lower lifting arm 146 and upper lifting arm 147. One or
both of such front and rear hitches are found on the typical
tractor.
Fig. 11 shows a specific embodiment of an appropriate
lifting arrangement 148 for use with a conventional three-
point hitch (not shown) having two lower lift arms 146 and one
upper lift arm 147. A first auxiliary frame 150 can be
inserted into rearward-facing openings of the tube-shaped side
frame members 16, 18 of the operator's platform 12. A second
auxiliary frame 152 supports the first auxiliary frame 150 and
transmits the lifting motion of the lifting arms 146, 147 to
the first auxiliary frame 150 and thereby also to the
operator's platform 12. The second auxiliary frame 152 is
provided with outwardly extending support shanks 154, 156 by
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which it is supported on the two lower lifting arms 146. The
upper lifting arm 147 is hooked into an eye 158 in the second
auxiliary frame 152. On its upper end, the second auxiliary
frame 152 carries two cylindrical rolls 160, 162 to equalize
relative horizontal motions.
While the invention has been described in conjunction
with a specific embodiment, it is to be understood that many
alternatives, modifications and variations will be apparent to
those skilled in the art in light of the foregoing
description. Accordingly, this invention is intended to
embrace all such alternatives, modifications and variations
which fall within the spirit and scope of the appended claims.
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