Note: Descriptions are shown in the official language in which they were submitted.
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HEADER FLOTATION SYSTEM FOR AN AGRICULTUR~L MACHINE
BACKGROUND OF THE INVENTION
1 The invention relates to a flotation system for a
header of an agricultural machine and although it will be
discussed primarily in relation to combine harvesters, it is to
be understood that it is applicable to any other type of
agricultural machine which employs a header, such as a forage
harvester, for example.
Combine harvesters, particularly the self-propelled
type, are equipped to utilise a variety of crop-gathering
headers, including headers specifically designed for harvesting
corn, cereal grains or soy beans, for example. Normally, these
headers are attached to the forward end of a feeder housing
which is a structure used to convey crop material from the
header to a base unit of the combine harvester for further
harvesting treatment. ~s is shown in U.S. Reissue Patent No.
26,512, the forward end of the feeder housing can be constructed
so that the header can be quickly and easily attached thereto.
Usually, the feeder housing structure is rectangular in cross
section and includes a rectangular crop inlet opening at the
eorward end which matches with a crop outlet opening of a header
attached to the feeder housing.
With the modern trend of developing headers of
increasingly larger sizes, providing a ready capability for the
headers to follow the contours of the ground is vital. One type
of prior art leveling or flotation mechanism, such as disclosed
in U.S. Patent No. 3,981,125, involves the twisting of the
feeder housing structure about the generally fore-and-aft
extending centerline thereof to effect an associated lateral
floating movement of the header. Also hillside combine
harvesters have been developed to allow the header to follow
slopes of up to 45%. Such hillside combine harvesters have been
known to utilise a side pivot mechanism, as disclosed in U.S.
Patent No. 3,731,470, or a center-mounted pivot connection
directly between the header and the feeder housing as disclosed
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.
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1 in U.S. Patent No. 2,780,903; the latter arrangement involving a
specific circular or semi-circular opening between the feeder
housing and the header.
Problems that have been encountered with these prior
art lateral float mechanisms include a difficult sealing
situation between the feeder housing and the base unit as the
feeder housing is twisted relative to the base unit. The
twisting of the feeder housing also results in a twisting of the
feeder housing drive mechanism, which in turn also increases
wear and reduces the life of the drive chains or the like.
Another problem encountered is the matching of different types
of headers to different feeder housing structures. This problem
is particularly relevant to feeder housings having specially
shaped crop inlet openings.
In other known header flotation systems use is made of
one or two hydraulic actuators connected between the header and
the base unit of a machine to pivot the header in a transverse
direction around a generaly fore-and-aft pivot axis and which
are interconnected hydraulically with a header weight
compensation device including control actuators together with a
hydro-pneumatic accumulator which effect raising and lowering of
the header. In operation, the hydraulic system, inclusive the
hydro-pneumatic accumulator is pressurized at a operating
pressure such that the ground contact pressure of the header is
minimal. This allows the header to follow the irregularities in
the ground contour by as well raising or lowering the complete
header as by pivoting the header in the transverse direction
depending on the size of the irregularities and on the location
thereof relative to the header. With headers having a weight
imbalance, such as grain headers having the drive means located
at one side, a single flotation actuator can be used at the side
of the drive means, but with balanced headers, two flotation
actuators are used, one at or towards each side of the header.
In still another known header flotation system such as
disclosed in U.S. Patent No. 3,386,235, the header is formed in
two parts which can pivot independently from each other and
lZ872Z2
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1 relative to the feeder housing around respective fore-and-aft
extending pivot axes. These parts also can be raised or lowered
in unison togethee with the feeder housing upon which they are
mounted, around a transverse pivot axis. A hydraulic suspension
system, including cylinders supporting the feeder housing with
the header thereon on the base unit and further cylinders
supporting the header portions on the feeder housing, is coupled
to a hydraulic control mechanism which is actuated by variations
in hydraulic pressure in the respective cylinders in response to
corresponding movements of the header, respectively the
constituent portions thereof over undulations in the ground. The
arrangement is such that said variations in pressure transmitted
to the control mechanism cause the control mechanism to allow
hydraulic pressure fluid to flow to or from the respective
cylinders so as to compensate for said variations and tend to
maintain a substantially constant hydraulic pressure in the
respective cylinders. Hydro-pneumatic accumulators, operating at
the system pressure, are coupled to the various cylinders for
assisting in a smooth following of the ground irregularities by
the header and the constituent portions thereof.
With the latter two systems, the header must always be
in contact with the ground at least at some point along its
length so that these headers cannot be set to operate at a given
stubble height, for example, which is a disadvantage. This is
not so with an automatic header height and lateral flotation
control system such as disclosed in the co-pending European
patent application no. 86.200.600 and which uses sensors on the
underside of the header. Such sensors produce electrical signals
for controlling the flotation actuators via electro-hydraulic
valves, thus making the system automatic. However, other
disadvantages arise with such automatic systems, the main one of
which is that they are slow acting. Furthermore, these systems
are expensive and the sensors thereof can suffer damage when the
header encounters a large obstruction and the header tilting is
too slow to clear this obstruction smoothly. The slow-acting
nature of such automatic systems also can place excessive
lZ~Z~Z
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1 torsional forces on the header and front end o~ the machine to
which it is fitted (for example the feeder housing of a combine
harvester) when the header tilts on meeting an irregularity in
the ground and until the system has responded and effected the
required flotation to compensate. Although an automatic system
can operate with the header off the ground because it is not
part of a header weight compensation system, it cannot be set to
give any desired initial position of the header which deviates
from the nominal position of the header because the electro-
hydraulic control valves for the flotation actuators can only beset through the sensors.
SUMMARY OF THE INVENTION
The instant invention is directed to a lateral combine
header flotation system for pivoting the header about a
generally fore-and-aft extending axis and which includes a
single hydraulic actuator extending between the header and the
base unit (i.e. the feeder housing of the base unit) and which
is operable to position the header in a nominal position
intermediate opposite extreme positions prior to starting
flotation operation. This flotation system further also
comprises an energy storage means in the form of a hydro-
pneumatic accumulator coupled to the flotation actuator and
which is pressurized at a pressure greater than the working
pressure which is present in the actuator when the header is in
its nominal position and meets no obstruction whereby this
energy storage means becomes operative upon pivotal movement of
the header in one direction and becomes inoperative upon pivotal
movement of the header in the opposite direction when the header
meets an obstruction causing the one or the other of said
pivotal movements. The arrangement is such that, when the header
pivots in said one direction, the actuator retracts so that the
energy storage means stores the energy created by the flow of
hydraulic fluid out of the actuator and then releases that
energy to restore the header to its nominal position when the
header is free to move, i.e. when the header has cleared the
lZ~72Z2
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1 obstruction causing said pivotal movement. When the header
pivots in said other direction, the energy storage means remains
inoperative and as such allows the header so to pivot and return
to its nominal position by making use of external return forces
only.
This hydraulic system is generally a one-way system to
the extent that the energy storage means is operative in one
direction only. Also, energization of the flotation actuator
pivots the header in one direction only and use has to be made
of an external return Eorce in the form of either a header
imbalance, a spring force or a hydraulic coupling to the header
suspension system to pivot the header in the opposite direction.
To make the above-described lateral header flotation
system more universally applicable, the harvester may comprise:
a mobile base unit adapted for movement over the
ground,
a transversely extending crop harvesting header
supported from the base unit for allowing pivotal movement about
a generally fore-and-aft axis of the machine, and
a lateral flotation system for pivoting the header
about the ~enerally fore-and-aft axis and including:
a) a two way hydraulic actuator means extending
between the header and the base unit for pivoting the header in
the one or the other direction and positioning the header in a
nominal position intermediate opposed extreme positions prior to
starting flotation operation,
b) a pressure source coupled by a pair of pressure
fluid supply lines to the hydraulic actuator means; and
c) energy storage means connected to the hydraulic
actuator means.
The harvester is characterized in that the energy
storage means is in the form of a hydro-pneumatic accumulator
coupled to each one of the pressure fluid supply lines and
pressurized at a pressure greater than the working pressure of
the hydraulic actuator means for pivoting the header in the one
or other direction; the arrangement being such that, when the
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1 header is positioned at a nominal position and meets an
obstruction, said header is permitted to temporarily pivot in
the one or other direction away from its nominal position for
moving over said obstruction; this pivotal movement resulting in
the gas in one hydro-pneumatic accumulator being temporarily
compressed by the flow of pressure fluid out of the actuator
means to store energy, this pressure fluid subsequently being
released back to the actuator means to restore the header to its
nominal position upon the header clearing the obstruction and;
the gas volume in the other hydro-pneumatic accumulator
remaining unchanged during this pivotal movement away from, and
back to the nominal position whereby said other hydro-pneumatic
accumulator remains inoperative under this condition.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages of this invention will become apparent
upon consideration of the following detailed disclosure of the
invention, especially when taken in conjunction with the
accompanying drawings wherein:
Fig. 1 is a front elevational view of a self-propelled
combine harvester and attached grain header, incorporating the
principles of the instant invention, components being broken
away;
Fig. 2 is a cross-sectional view of the forward
portion of the combine harvester including the header and feeder
housing, taken along the line II-II of Fig. 1,
Fig. 3 is a side elevational view, to a larger scale,
of the forward portion of the feeder housing,
Fig. 4 is a hydraulic circuit diagram of the header
flotation system in accordance with the invention, and
Figs. 5 - 8 are views similar to Fig. 4 but showing
alternative arrangements.
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1 DETAILED DESCRIPTION OF THE PREFERRED EMsoDIMENT
Referring to Figs. l and 3 of the drawings, left hand
and right-hand references are used as a matter of convenience
and are determined by standing at the rear of the machine and
facing the forward direction of travel. The combine harvester is
generally indicated at 10 and comprises a base unit 12,
including crop-treating means (not shown) for separating the
desired crop material from the waste crop material, a detachable
crop-gathering header 20 located forwardly of the base unit 12,
a cab 14 elevated above the header 20 for full view of the crop
harvesting process, wheels 16, and a feeder housing 30 for
conveying cut crop material from the header 20 rearwardly to the
base unit 12 for treatment by the crop-treating means which, for
example, can be a conventional threshing unit or the more
recently developed rotary type axial flow threshing unit.
Referring now to the cross-sectional view of Fig. 2, a
more detailed view of the general inner workings of the header
20 and the feeder housing 30 can be seen. The header 20 includes
a cutterbar 22 operable to sever crop material from the stubble.
A reel 24 is disposed above and forwardly of the cutter bar 22
to sweep crop material over the latter and transport it
rearwardly to crop consolidating means 26 in the form of a
consolidating auger 27.The consolidating auger 27 converges crop
material towards a centrally disposed crop discharge opening for
discharge to the feeder housing structure 30. A frame 28 of the
header 20 includes a transversely disposed main header beam 29
used to support the header 20 from the feeder housing 30.
As can also be seen in Fig. 2, the feeder housing 30
has a forwardly extending, elongated body portion 32 defined by
a rearward end 33 pivotally attached to the base unit 12 and a
forward end 34 adjacent the header 20 for connection thereto.
The body portion 32 includes a passageway 36 therethrough,
terminating in a crop inlet opening at the forward end 34, for
allowing crop material to be transported rearwardly from the
forward end 34 to the rearward end 33. Crop conveying means 40
in the form of an endless chain and slat apron conveyor 41 is
1~72Z2
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1 positioned within the passageway 36 and is operable to transport
the crop material rearwardly. The apron conveyor 41 is driven by
a drive shaft 43 positioned at the rearward end 33 and is
supported on a driven shaft 44 adjacent the forward end 34. The
height of the header 20 relative to the ground is controlled by
a header lift means in the form of a pair of hydraulic actuators
48 interconnecting the feeder housing 30 and the base unit 12.
sy extending the actuators 48 the rearward end 33 of the feeder
housing 30 is pivoted about the drive shaft 43 whereby the
header 20 is lifted from the ground without significantly
changing the discharge point of the apron conveyor 41 relative
to the base unit 12. These hydraulic actuators 48 may be part
either of an automatic header height control mechanism of any
type known in the art or of a header weight compensation
mechanism equally known in the art.
Referring now to Fig. 3, an enlarged view of the
forward end 34 of the feeder housing 30 showing a front face
member 50 and a detached header 20 in phantom proximate thereto,
can be seen. The front face member 50 includes an offset section
53 substantially registrable with the main header beam 29 for
detachably supporting the header 20 in an operable position on a
cradle 58 still to be described hereafter.
A lateral flotation system 57 for the header is best
seen in Figure 3 and comprises the cradle 58 already mentioned
and which is pivotally attached to the front face member 50 at
the forward end 34 of the feeder housing 30 by a pivot pin 59.
The cradle 58 comprises a nesting portion 64 for the main header
beam 29 at a position generally within the offset section 53 of
the front member 50. The components so far described are similar
to those of the combine harvester illustrated in U.S. Patent No.
4,253,295 to which reference is made and which discloses further
details of construction which are not relevant to the present
invention.
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g
1 In accordance with the present invention, the
flotation mechanism 57 further comprises a hydraulic actuator 60
which, in the preferred embodiment, is of the single acting type
and the rod 61 of which is pivotally attached to the cradle 58
by a pin 62 extending between a pair of lugs 63 depending from
the nesting portion 64 of the cradle 58 which releasably
receives the main header beam 29. The cylinder 65 of the
actuator 60 is pivotally attached by a pin 66 to a bracket 67
fixed to, and extending rearwardly from the front face member 50
of the feeder housing 30 at the forward end 34 thereof and
against which the lower portion of the cradle 58 is movably
supported. The header 20 is firmly coupled to the cradle 58 for
being transversely pivotable therewith after the main beam 29 of
the header 20 is positioned in the nesting portion 64 of the
cradle 58. The actuator 60 is thus effectively connected between
the main body 12 of the machine and the header 20, the actuator
60 being disposed at the side of the feeder housing 30
corresponding to the side of the header 20 at which the header
drive is fitted, i.e. at the side of the imbalance.
As can best be seen in Fig. 4, the actuator 60 is
connected hydraulically via a restrictor 68 to an energy storage
device in the form of an accumulator 69 (mounted below the cab
14) and also connected, via a restrictor 71, to a three-position
spool valve 72 to which is connected a hydraulic pump 73 for the
system and a connection to tank 74. In the central position of
the valve 72 (the position illustrated) the pump 73 is vented
directly to the tank 74 and the actuator 60 is only connected to
the accumulator 69. If the valve spool is moved to the right as
seen in Fig. 4, the actuator 60 is vented to the tank 74 and if
it is moved to the left, the actuator is subjected to system
pressure from the pump 73. It should be noted that, under normal
operating conditions, the pressure in the accumulator 69 is
higher than that in the actuator 60. Preferably this difference
is in the range of 10 bar.
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l It also should be noted that the flotation system thus
described is totally independent from the header lifting system
although it may be used in combination with an automatic header
height control mechanism. It even may be used in combination
with a header weight compensation mechanism although the
combination with an automatic header height control mechanism is
preferred.
In operation of the machine and provided the hydraulic
actuators 48 are not part of a header weight compensation
mechanism, the feeder 30 can be set at any required height
relative to the ground, including at a height whereat the header
20 makes contact with the ground, by operating the actuators 48
accordingly. In the event the hydraulic actuators 48 are part of
a header weight compensation mechanism, the header 20 then of
course should be positioned to contact the ground surface.
Additionally and prior to commencing operation, the
operator also actuates the valve 72 to pressurize the hydraulic
flotation circuitry normally so as to position the header 20 in
its nominal or level position relative to the base unit 12. sy
doing so, an operating pressure is established in the actuator
60 which is sufficient to pivot the header 20 away from its rest
position towards the intermediate nominal position and thus,
which compensates the header imbalance. Indeed, without this
pressurizing, the header 20 is positioned in an inclined
position with the rod 61 fully retracted within the cylinder 65
of the actuator 60 and with the end of the header 20 supporting
the header drive means ti.e. the end of the header 20 at which
the imbalance is situated) being situated at a level below the
other end due to the header imbalance. As already mentioned, the
operating pressure thus established in the actuator 60 is less
than the gas pressure in the hydro-pneumatic accumulator 69
whereby the above described initial setting of the header does
not vary the gas volume in the accumulator 69 which thus fills
- the entire accumulator body.
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1 Once the operating position of the header 20 has been
set, the machine moves forwardly and commences harvesting in the
conventional manner. Should the header 20 meet a transverse
irregularity in the ground, which may be a temporary
transversely offset obstruction or a transverse slope, for
example, then one side of the header will rise and the opposite
side will drop in view of the pivotal mounting of the cradle 58
about the pivot 59 so as to permit the header 20 to move over
and clear said irregularity. Assuming this pivotal movement of
the header 20 is such as to move the rod 61 of the actuator 60
into the cylinder 65 (i.e. the actuator 60 contracts) the fluid
thus forced out of the cylinder is forced into the accumulator
69 and increases the pressure therein as the connection to the
tank 74 is blocked by the central valve position. If the
irregularity is only temporary, then when it is cleared by the
header 20, the latter will pivot back to its former (nominal)
position under the pressure of the accumulator 69, which is
sufficient to overcome any frictional resistance in the pivotal
mounting of the header. The gas in the accumulator expands until
it fills the accumulator volume completely again and thus untilall pressure fluid, which previously was urged into the
accumulator by the irregularity, is urged back to the flotation
actuator 60. Thus, the header 20 always is returned to the same
nominal position as initially set by the operator when the
header 20 has cleared the obstruction.
Should the header 20 pivot in the opposite direction,
the actuator 60 is extended as the rod 61 is pulled out of the
cylinder 65 and a partial vacuum is created therein (a breather
valve may be fitted if desired in this respect). This vacuum is
created because the accumulator 69 is unable, because of its
nominal setting, to urge more hydraulic pressure fluid into the
actuator 60 to the extent that the gas in the accumulator 69
already occupies the entire volume of the accumulator 69. When
the header 20 is free to return to its former position, it does
so under the weight imbalance of the header in the illustrated
embodiment, this weight imbalance equally being sufficient to
12~72~2
- 12
1 overcome any frictional resistance in the pivotal mounting of
the header 20, whereby also starting from this side of the
nominal position, the header always is returned to its nominal
setting when the ground surface beneath the header permits this.
From what precedes, it will be understood that the
hydro-pneumatic accumulator 69 as used in the present invention
on the one hand and the header imbalance on the other hand
effectively act as "power sources" for always returning, without
any hesitation, the header 20 back to the same nominal position
previously set by the operator when the ground surface below the
header 20 permits this to happen, i.e. when any irregularities
in the ground have been cleared by the header. These returning
forces are sufficiently large to overcome any frictional
resistance in the pivotal mounting of the header which
inherently is present and which, in prior art arrangements also
using a hydro-pneumatic accumulator, prevent the header to
return to the nominal position when the deviation from said
nominal position is rather small. Unlike in these prior art
arrangements where the hydro-pneumatic accumulator has a working
pressure which corresponds to the working pressure of the
flotation actuator and thus acts mainly to absorb hydraulic
pressure fluid urged out of the flotation actuator without
substantially varying the working pressure and whereby it
becomes a rather "passive" component, the hydro-pneumatic
accumulator according to the present invention, is rather
"active" in the header flotation operation to the extent that it
truely forms a power source in the sense as already described
which is operable to always return the header to the same
nominal position even when the deviation therefrom is minimal.
If the operator wishes to set the header 20 at an
angle to the nominal horizontal position, he operates the valve
72 to one side or other of the central position so as to
pressurise or vent the actuator 60 to give the desired header
tilt perhaps to compensate for a permanent irregularity in the
field being harvested. When this control of the header 20 is
being exercised, the restricter 71 damps header movement so that
,
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1 the latter is controlled. Also restrictor 68 has a stabilizing
function as will be readily understood by any one skilled in the
art.
In the preferred embodiment as described above, the
header is of the type having an imbalance due to the header
drive means being provided adjacent one end thereof, this
imbalance being used for providing header flotation in one
direction. However, the principles of the present invention
also can be applied to a fully balanced header (such as e.g. a
corn header). In this case the header imbalance may be replaced
by a spring force provided by spring means extending between the
cradle 58 and the feeder housing 30 at the side of the latter
opposite to the side at which the actuator 60 is provided. These
spring means are arranged to pivot the cradle 58 with the header
20 thereon in the direction around the pivot 59 so as to retract
the rod 61 into the cylinder 65 of the actuator 60.
In a further alternative embodiment shown in Fig. 5
the return force acting on the flotation actuator 60 is obtained
by a hydraulic coupling of the flotation actuator 60 to the
header lifting actuators 48 below the plungers thereof. In this
case, the flotation actuator 60 is of the double acting type and
is coupled at its plunger rod side to the header lifting
actuators 48; the other side of the flotation actuator 60 being
coupled to the hydro-pneumatic accumulator 69 and the valve 72
in the same manner as described in connection with Fig. 4. The
pressure reigning in the header lifting actuators 48 when the
header is in the operative position, is communicated to the
plunger rod side of the flotation actuator 60 where it causes a
return force oriented opposite to the flotation force resulting
from the pressure below the plunger thereof and which acts in
the same manner as the imbalance of the preferred embodiment and
as the resilient return force of the spring means of the first
alternative embodiment. The arrangement again is such that the
work pressure below the plunger of the flotation actuator is
less than the gas pressure in the accumulator 69. It will be
appreciated that this alternative arrangement operates in the
same manner as the preferred embodiment and that therefore a
detailed description of the operation is not necessary.
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1 The hydraulic coupling between the flotation actuator
60 and the header lifting actuators 48 may comprise a two-
position spool valve 80 for enabling the operator either to
establish the coupling as described in case the harvester is
equipped with a balanced header, or to interrupt this coupling
in case the harvester is equipped with an unbalanced header, in
which case the header imbalance provides the return force as
described in connection with Fig. 3.
From what precedes, it will be clear to one skilled in
the art that the arrangements illustrated in Fig. 4 and 5
basically are "one-way" systems to the extent that, on the one
hand, the hydro-pneumatic accumulator is operative in one
direction only and, on the other hand, energization of the
flotation cylinder pivots the header also in one direction only
whereby use must be made of external forces provided by either a
header imbalance, a spring or a hydraulic coupling to the header
suspension system to pivot the header in the opposite direction.
This may be felt as a shortcoming to the extent that such
systems are not readily universally applicable.
With reference to Fig. 6-8, three "two-way' or "double
acting" lateral header flotation systems now will be described
in more details. With these arrangements lateral flotation
positively is controlled in both directions by means of energy
storage means.
Turning now specifically to Fig. 6 which schematically
illustrates a first "two-way" embodiment of the header flotation
system, it will be noticed that a two-way hydraulic actuator
means in the form of one double-acting cylinder 60 extends
between the header 20 and the base unit 12 (actually the feeder
- 30 housing 30). This double-acting hydraulic cylinder 60 is
operable to pivot the header 20 in the one or other direction
around the pivot 59 for positioning said header in a nominal
position intermediate opposed extreme positions prior to
starting flotation operation. To this end, the flotation
cylinder 60 is coupled via a pair of pressure fluid supply lines
75 and the valve 72 to the pressure source 73. One pressure
, :
lZ~7222
- 15
1 fluid supply line 75 is coupled to the plunger side and the
other pressure fluid supply line 75 is coupled to the plunger
rod side of the cylinder 60. The valve 72 is a conventional
three-position, four-way electromagnetic valve which further
also is coupled to the reservoir 74. In accordance with the
present invention, a hydro-pneumatic accumulator 69 is coupled
to each one of the pressure fluid supply lines 75. Both
accumulators 69 are pressurized at pressures greater than the
working pressures of the cylinder 60 required to pivot the
header in the one or other direction. Preferably these
differences between the working pressures in the cylinder 60 and
the gas pressures in the accumulators 69 are at least 10 bar.
To the extent that the working pressures in the
cylinder 60 at the plunger and plunger rod sides may be
different, the gas pressures in the accumulator 69 equally may
different, although for practical reasons, these gas
~ res may be set at the same valve; the only requirement
b~lu~ that these gas pressures exceed the working pressures with
an amount which is sufficient to overcome friction forces in the
pivotal mounting of the header as well as eventual header
imbalances. From what precedes it thus will be appreciated that,
when the header is in the nominal position and meets no
obstruction, the gas in the respective hydro-pneumatic
accumulators 69 occupies the entire volume thereof. Further, it
also will be clear that, by utilizing the valve 72 the header 20
is selectively positionable, in any one nominal position from a
range of positions inbetween two extreme positions without
changing the gas pressure in the accumulators 69.
The hydraulic circuitry further also comprises a pilot
operated check valve 76 which assists in isolating the flotation
cylinder 60 and the accumulator 69 completely from the reservoir
74 when the valve 72 is in its neutral (central) position.
Without this check valve 76 pressure fluid possibly could leak
back to the reservoir 74 when the valve 72 is in its shut off
position. This would adversely affect the flotation operation.
1;Z~7Z~2
- 16
1 Flow restrictors 71 are included in both pressure
supply lines 75 between the check valve 76 and the coupling of
the accumulators 69 to said pressure supply lines 75 to damp the
pivotal movement o~ the header 20 upon actuation of the valve 72
in the one or other direction. These flow restrictors 71 should
not affect the interaction between the flotation cylinder 60 and
the accumulators 69.
When commencing operation, the operator may actuate
valve 72 in the one or other direction to position the header 20
in any desired nominal position if this position is not already
installed. Should the header 20 subsequently meet a transverse
irregularity in the ground during operation of the harvester,
then one side of the header will rise and the opposite side will
drop to permit the header to move over and clear said
irregularity. Assuming this pivotal movement of the header 20 is
such as to contract the cylinder 60, the fluid thus forced out
of the plunger side of the cylinder is forced into the
corresponding accumulator 69 and increases the pressure
therein. Simultaneously, a partial vacuum is created in the
cylinder 60 at the plunger rod side thereof to the extent that
the gas in the accumulator 69 coupled to this plunger rod side
cannot expand further in as much as this gas already occupies
the complete volume of said accumulator. During this operation,
the valve 72 of course is in its neutral shut off position,
which is why the one accumulator 69 absorbs pressure fluid from
below the plunger of the cylinder 60 and the other accumulator
69 remains inoperative. When subsequently the irregularity in
the ground is cleared by the header 20, the latter will pivot
back to its former (nominal) position under the pressure of the
accumulator 69 which is coupled to the plunger side of the
cylinder 60 and which is sufficient to overcome any frictional
resistance in the pivotal mounting of the header 20. The gas in
this accumulator 69 expands until it fills the accumulator
volume completely again and thus until all pressure fluid, which
previously was urged into said accumulator 69 by the
irregularitiy, is urged back to the plunger side of the
flotation cylinder 60. The vacuum at the plunger rod side of the
cylinder 60 permits this return movement to occur.
.
lZ~Z~2
- 17
l Should the header 20 pivot in the opposite direction,
the cylinder 60 is extended as the plunger rod 61 thereof is
pulled out of the cylinder body 65 and a partial vacuum now is
created at the plunger side on the one hand while that pressure
fluid from the plunger rod side of the cylinder 60 is urged into
the accumulator 69 coupled to said plunger rod side on the other
hand. It will be readily appreciated by one skilled in the art
that this condition is practically identical to the condition
described hereabove and thus that, once the header 20 has
cleared the irregularity, the latter again automatically returns
to its nominal position by the action of the accumulator 69
coupled to the plunger rod side of the cylinder 60. Thus, the
header 20 always is returned to the same nominal position as
initially set by the operator when the header 20 has cleared any
transverse obstruction.
From what precedes it will be appreciated that the
header flotation system including the two hydro-pneumatic
accumulators 69 operates independently of the direction of the
deviation of the header 20 from its nominal position. In other
words, the one or the other accumulator 69 becomes operative,
depending on the direction of said deviation, to restore the
header 20 to its nominal position as soon as it is permitted to
do so by the clearing of any ground irregularity. It further
also will be noticed that with this "two-way" system according
to Fig. 6, operation of the flotation system does not rely on
external forces such as can be obtained from a header imbalance,
a spring or a hydraulic coupling to the header suspension
mechanism. Thus, this "two-way" flotation mechanism is more
universal in as much as it can be utilized in combination with a
balanced header as well as with an unbalanced header.
Turning now to Fig. 7, it will be noticed that the
only difference between the embodiment shown therein and the
embodiment shown in Fig. 6 is the replacement of the one double
acting cylinder 60 according to Fig. 6 by a pair of single
acting cylinders 60 according to Fig. 7. One of these cylinders
60 is provided at each transversely opposite side of the pivot
~Z1~72~2
- 18
1 axis 59 and is connected to a corresponding pressure fluid
supply line 75. The operation of this embodiment is very similar
to the operation of the embodiment shown in Fig. 6 and is such
that any temporary pivotal displacement of the header 20 in the
one or other direction away from its nominal position as a
result of the header 20 encountering an obstruction, causes one
hydraulic cylinder 60 to retract and the other hydraulic
cylinder 60 to extend (provided the plunger of this cylinder is
positively coupled to the header). The retraction of the one
cylinder 60 results in the gas in the corresponding hydro-
pneumatic accumulator 69 to be compressed by the flow of
hydraulic fluid out of said one hydraulic cylinder to store
energy in said accumulator 69. This energy subsequently is
released back to said one hydraulic cylinder 60 for restoring
the header 20 to its nominal position upon the header clearing
the obstruction which previously caused the pivotal deviational
movement. ~uring this pivotal movement of the header 20 away
from its nominal position, the other cylinder 60 is extended, as
already said. This causes a vacuum to be established therein
which however has no effect on the flotational operation of the
header 20. When the header 20 subsequently returns to its
nominal position, this vacuum merely is eliminated again as is
the case in the arrangement according to Fig. 6.
When using two single acting hydraulic cylinders 60 as
shown in Fig. 7 it is possible to avoid the creation of a vacuum
in the one or other cylinder 60 when the flotation system is
operational. To accomplish this, it is sufficient to
telescopingly couple the plungers 61 of the cylinders 60 to the
header 20 in a manner to permit the corresponding portions of
the header 20 to pivot away from anyone of said plungers 61
without causing a corresponding extension of the cylinders 60.
This is schematically shown in Fig. 7 and is realized by the use
of a pair of sleeves 77 which are attached to the header 20 and
which each receive the plunger 61 of a corresponding hydraulic
cylinder 60. When the header 20 is in any nominal position, the
plungers 61 of the cylinders 60 abut with the bottom of the
2~'2
-- 19
1 respective sleeves 77. When the header 20 temporarily is pivoted
away from this nominal position in the one or other direction,
one sleeve 77 pushes the plunger 61 into the cylinder body 65 of
the corresponding hydraulic cylinder 60 while that the other
sleeve 77 telescopes relative to its corresponding plunger 61
and away from the corresponding cylinder body 65. Thus, as
described before, when the header 20 is pivoted in the one or
other direction, one cylinder 60 is caused to retract, which
results in the gas in the corresponding accumulator 69 to be
compressed. When subsequently the gas in this accumulator 69 is
permitted to expand again, the plunger 61 of the corresponding
cylinder 60 is caused to extend which in turn causes the header
20 to return to its nominal position. During these pivotal
movements of the header 20, the plunger 61 of the other
hydraulic cylinder 60 is not moved by virtue of the telescopic
coupling thereof to the corresponding sleeve 77 and thus, unlike
_.. the arrangement described herebefore, a vacuum is not created
in this other hydraulic cylinder 60.
Turning now finally to Fig. 8, it again will be seen
29 that the arrangement illustrated therein is basically the same
as the arrangement according to Fig. 7, except for the fact that
the single-acting hydraulic cylinders 60 of Fig. 7 are replaced
by double-acting cylinders 60. In this embodiment, any one
pressure fluid supply line 75 is connected both to the plunger
side of one cylinder 60 and to the plunger rod side of the other
cylinder 60.
Also the plungers 61 now are positively coupled to the
header 20. Consequently, when the header is caused to pivot in
the one or other direction, one cylinder 60 is contracted and
the other cylinder 60 is extended. Pressure fluid which is urged
out of the plunger side of the one cylinder 60 which is
contracted and out of the plunger rod side of the other cylinder
60 which is extended, is urged into the accumulator 69
associated with said sides of the respective cylinders 60. Gas
in this accumulator 69 thus is compressed to store energy
therein. This energy is released back to said opposite sides of
1~7222
- 20
1 said cylinders 60 for restoring the header to its nominal
position upon the header clearing the obstruction, which caused
the initial pivotal movement. Thus the one cylinder 60 which
previously was contracted, is extended again and the other
cylinder 60 which previously was extended is retracted again by
the release of said energy from said accumulator 69. During this
pivotal movement of the header away from and back to its nominal
position, a vacuum is established in the pressure fluid supply
line 75 associated with the other hydro-pneumatic accumulator 69
to the extent that the gas in this other accumulator 69, under
this condition, occupies the entire volume thereof and thus no
hydraulic pressure fluid can be made available from said
accumulator 69 to eliminate said vacuum. However, the creation
of this vacuum does not noticeably affects the flotation
operation of the header 20.
In summary, it thus will be seen that the present
invention provides a very simple but highly effective header
Elotation system which suffers none of the disadvantages of
known systems in that both the operating height and orientation
can be set without difficulty. This means that the header can
still be operated in a weight compensation mode if desired. This
also means that, if the header is set to operate at a height
above the ground and thus, if there is no permanent contact of
the header with the ground , the header nevertheless always
returns to the same nominal position previously set by the
operator after the header having cleared an obstruction. This
would not be the case in prior art arrangements equipped with a
hydro-pneumatic accumulator; this accumulator in these
arrangements not providing enough power to overcome frictional
resistance in the pivotal mounting of the header when the
deviation from the nominal position is minimal.
Furthermore, the system is very fast acting, whereby
peak loads and high torsional forces on the header and/or front
end of the machine to which it is fitted are avoided. This, in
turn results in a structure which is less subject to damages and
is carefree. Also, the flotation system is very simple in design
as well as in operation and is inexpensive to manufacture.
1~7222
- 21
1 It will be understood that changes in the details,
materials, steps and arrangements of aparts which have been
described and illustrated to explain the nature of the invention
will occur to and may be made by those skilled in the art upon a
reading of this disclosure within the principles and scope of
the invention. The foregoing description illustrates the
preferred embodiment of the invention; however, concepts, as
based upon the description may be employed in other embodiments
without departing from the scope of the invention. Accordingly,
the following claims are intended to protect the invention
broadly, as well as in the specific form shown.
. '~. .
