Abstract:
An agricultural working machine has a vehicle, a front attachment guided such that it is swivelable about an axis in a direction of travel during a harvesting operation, a frame on which working tools are mounted, and an element provided on a chassis of the vehicle and/or the front attachment for applying a force that counteracts a swivel motion of the vehicle or the front attachment induced by a parameter selected from the group consisting of driving speeds, uneven terrain and both.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2010 021 133.8 filed on May 21, 2010. These German Patent Applications , whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to an agricultural working machine comprising a carrier vehicle and a front attachment mounted thereon, e.g. a combine harvester or a forage harvester, comprising a header. In efforts to increase the productivity of harvesting work, headers having increasingly greater working widths have been developed in recent years. Widths exceeding 10 meters are no longer unusual. Such a header is generally mounted in the center on a feed drive of the carrier vehicle. if roiling motions of the header are induced during operation, high, destructive torques can occur on the suspension. The ends of the header can reach high speeds, and so, if they strike the ground, there is also the risk that the header will become damaged. 
         [0003]    Document EP 1 611 781 B1 makes known a self-propelled harvesting machine, in the case of which the height of a front attachment is continually adjusted during operation to maintain a desired working height above the ground. in that particular case, the front attachment is supported by two wheels which can be retracted and extended using lifting cylinders, to adjust the working height of the front attachment. The lifting cylinders are double-acting and comprise chambers on the face-end and on the piston-ring side. The face-end side chambers of the two lifting cylinders are interconnected, and the piston-ring side chambers can be interconnected using control valves. Sensing straps disposed in front of the wheels detect the distance of the front attachment to the ground and thereby deliver information required to actuate the control valves. If a sensing strap detects a low area in the ground, the lifting cylinder of the wheel following same is extended and, simultaneously, the lifting cylinder of the opposite wheel is retracted in that hydraulic fluid from a pump is applied to the piston-ring side chamber of said latter lifting cylinder, flows out of the face-end side chamber of this lifting cylinder and into the face-end side chamber of the first lifting cylinder, and out of the piston-ring side chamber thereof to the tank. 
         [0004]    If the harvesting machine makes a turning maneuver, it is often necessary to lift the front attachment to avoid striking an obstacle. In this raised position, neither the sensing straps nor the wheels have contact with the ground. Rolling motions of the vehicle are transferred to the front attachment. The ends thereof can reach considerable speed due to their large distance from the roll axis. If, in the course of such a rolling motion, one of the wheels strikes the ground, the hydraulic fluid in the face-end side chambers of the lifting cylinders becomes highly pressurized. Since it cannot flow out and is incompressible, the lifting cylinders lock up. The resulting abrupt deceleration can cause damage to the front attachment. 
       SUMMARY OF THE INVENTION 
       [0005]    The problem addressed by the present invention is that of improving the operating safety of such an agricultural working machine. 
         [0006]    The problem is solved in the case of an agricultural working machine comprising a vehicle and a front attachment which is guided such that it can swivel about an axis in the direction of travel during the harvesting operation, and comprises a frame on which working tools are mounted, by providing means on the chassis of the vehicle or the front attachment for applying a force that counteracts a swivel motion of the vehicle or the front attachment induced by driving speeds and/or uneven terrain. 
         [0007]    Preferably these means act on the front attachment, since the mass thereof is less and thus the force or power required to suppress the swivel motion is less than if the aim were to suppress the swivelling of the vehicle. 
         [0008]    The means for applying a force to the front attachment, which counteracts a swivel motion of the front attachment, comprises at least two interspaced supports which are disposed on the frame in a vertically movable manner for supporting, in contact with the ground, at least a portion of the weight of the front attachment, and which can yield reversibly in order to apply a supporting force to counteract the swivel motion of the front attachment when at least one of the supports contacts the ground. Instead of yielding without force, or locking up upon contact with the ground, the supports therefore induce a gradual deceleration of the rolling motion of the front attachment, which prevents the frame from coming in contact with the ground, or at least dampens same to the extent that damage is prevented. 
         [0009]    The yielding of the supports should be reversible, to allow the supports to apply their damping effect if contact is made with the ground a second time. However, the speed of the reversing motion of the supports should be adapted to the elasticity of a connection between the vehicle and the front attachment, i.e. it should be so low that, after the front attachment undergoes a deflection relative to the vehicle, which caused a support to yield, the return motion of the front attachment driven by the elasticity of the connection causes the support to lose contact with the ground during the return motion. 
         [0010]    The maximum load-carrying capacity of the supports is preferably less than the weight of the front attachment, thereby ensuring that this weight is also carried in part by the elastic connection to the vehicle. 
         [0011]    In a first preferred embodiment, the supports comprise at least a first lifting cylinder, and the pressure in at least one chamber of the first lifting cylinder is limited by a pressure relief valve. Therefore, when the pressure in said chamber exceeds the limiting pressure of the pressure relief valve due to ground contact by the support, hydraulic fluid can flow out of the chamber, wherein energy is withdrawn from the motion of the front attachment in proportion to the limiting pressure and the outflowing quantity of hydraulic fluid. 
         [0012]    In a second preferred embodiment, the supports comprise at least one first lifting cylinder having a chamber connected to a first buffer, and, if the maximum load-carrying capacity is exceeded, hydraulic fluid can be displaced out of the at least one chamber and into the first buffer. 
         [0013]    In both embodiments, a coupling device can be provided between the supports so that, if one of the supports yields under load, the other support can be moved in the same direction as the first support. Such a design makes it possible to sum the load-carrying capacities of the individual supports; i.e., if only one of the two supports has ground contact, the load-carrying capacity thereof is as great as that of both supports when they both have ground contact. 
         [0014]    A coupling of this type can be embodied in particular in that the first and a second lifting cylinder are double-acting, and each comprises a first chamber which can be acted upon with hydraulic fluid to exert a downwardly directed force onto the support assigned to the particular lifting cylinder, and a second chamber which can be acted upon with hydraulic fluid to apply an upwardly directed force onto the support, and the coupling between the cylinders is established by the first chamber of the second lifting cylinder communicating with the second chamber of the first lifting cylinder. 
         [0015]    Since the pressure in the first chambers of the lifting cylinders supports the weight of the front attachment, the first chambers are preferably face-end side chambers, since they generally have a larger cross section than do piston-ring side chambers. The larger the cross section, the lower the pressure required in the first chambers to generate the setpoint supporting force. 
         [0016]    In the case of the first embodiment, it is sufficient for only the first chamber of the first lifting cylinder to communicate wtih the above-mentioned pressure relief valve, since the first chamber of the second lifting cylinder, when it yields, can release hydraulic fluid to the second chamber of the first lifting cylinder. 
         [0017]    To ensure that the motions of the first support and the second support are the same even though the cross sections of the face-end side chamber and the piston-ring side chamber of one lifting cylinder differ, the first lifting cylinder preferably has a larger cross section than does the second lifting cylinder, according to the first embodiment. 
         [0018]    A releasable non-return valve is preferably provided between the second chamber of the second cylinder and a tank. Such a non-return valve permits a support to yield at any time if the maximum load-carrying capacity thereof is exceeded, and in the blocked state can prevent the support from moving in the reverse direction. 
         [0019]    The second embodiment is preferably symmetrical in terms of the connections between the lifting cylinders, i.e. the second chamber of the second lifting cylinder communicates with the first buffer, and the first chamber of the second lifting cylinder and the second chamber of the first lifting cylinder communicate with a second buffer. 
         [0020]    In the state of equilibrium, according to this embodiment, the pressures in the first and second chambers of the two lifting cylinders are the same, and a supporting force results from the fact that the two chambers have a smaller cross section than do the first chambers. 
         [0021]    A tip of the support that touches the ground can be designed as a skid or a roller. 
         [0022]    Means for detecting the vertical position can be provided on at least one of the supports, to implement automatic regulation of the working height of the front attachment on the basis of the vertical position detected as a result, as described in EP 1 611 781 B1, for example. 
         [0023]    To absorb the fluctuating load of the front attachment, the vehicle can also be advantageously equipped with a crawler track assembly. 
         [0024]    Further features and advantages of the invention will become apparent from the description of embodiments that follows, with reference to the attached figures. In the drawings: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  shows a schematic depiction of an agricultural working machine according to the present invention; 
           [0026]      FIG. 2  shows a schematic depiction of a hydraulic system which supports the front attachment, according to a first embodiment; 
           [0027]      FIG. 3  shows a second embodiment of the hydraulic system; 
           [0028]      FIG. 4  shows the hydraulic system according to a third embodiment; and 
           [0029]      FIG. 5  shows a fourth embodiment of the hydraulic system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]      FIG. 1  shows a schematic view of an agricultural working machine according to the invention, comprising a vehicle  1  and a front attachment  2  mounted on a front side of vehicle  1 . The working machine can be, in particular, any type of self-propelled harvesting machine, in particular a combine harvester or a forage harvester, and front attachment  2  is a header adapted for the particular crop to be harvested. A frame of the header comprises, in a manner know per se, a floor plate  3  having movable knives on front edge  4  thereof, side panels  5 , and a rear panel  7 . A feed roller  6  is rotatably mounted between side panels  5 . A feed rake  8  of the vehicle engages at rear panel  7 . Feed rake  8  is resiliently supported on vehicle  1  and forms a four-joint connection between front attachment  2  and vehicle  1 , which permits rolling motions (i,e. swivel motions about an axis oriented in the direction of travel) of front attachment  2  relative to vehicle  1 , and upward and downward motions while retaining the orientation of front attachment  2  in three dimensions. 
         [0031]    A lifting cylinder  9  and  10  (hidden in  FIG. 1 ) is mounted on each of the side panels  5 , on connecting rod  23  of which—which is directed toward the ground—a skid  11  is installed. The two lifting cylinders  9 ,  10  are provided to support a portion of the weight of front attachment  2 ; the rest of the weight bears via feed rake  8  on the ground drive of vehicle  1 . 
         [0032]    In the usual case, said ground drive can comprise two or more axles having pneumatic wheels  12 ; in the present case, a crawler track assembly  13  provided at least on a front axle of vehicle  1  is preferable in order to compensate for the load of front attachment  2 , which fluctuates during operation. 
         [0033]      FIG. 2  is a schematic illustration of one half of a hydraulic system according to a first embodiment of the invention. Shown in the illustration is lifting cylinder  9 , wherein the support assigned to lifting cylinder  9  is formed in this case by connecting rod  23  of the lifting cylinder and, instead of the skid, is formed by a wheel  24  which is rotatably held by connecting rod  23 . In general, wheels or skids can be used in any of the embodiments described herein, and it is also feasible for an operator to be able to use either wheels or skids depending on the terrain and the crop. 
         [0034]    Lifting cylinder  9  comprises a face-end side chamber  16  and a piston-ring side chamber  17 . A pressure reducer  15  has a high-pressure port which is connected to a directional control valve  14 , a controlled port connected to face-end side chamber  16 , and a drain port which communicates via a port coupling T of front attachment  2  to a tank on board the vehicle. Directional control valve  14  has two inlets which can be connected selectively to the high-pressure port of pressure reducer  15 , and one of which communicates via port coupling T with the tank, and the other of which communicates via a port coupling P with the high-pressure outlet of a pump on board vehicle  1 . Piston-ring side chamber  17  is connected to port coupling T via a controllable non-return valve  21  which blocks the route from piston-ring side chamber  17  to port coupling T provided a high control pressure is not present at the high-pressure port of pressure reducer  15 . A second half of the hydraulic system, which is structurally identical to that shown in  FIG. 2 , is assigned to second lifting cylinder  10 . 
         [0035]    If front attachment  2  is operating and is guided at a low height over a field to be harvested, directional control valve  14  is located in the position shown in  FIG. 2 . A high pressure delivered by the pump is present at the high-pressure port of pressure reducer  15  and at the control port of non-return valve  21 . Chamber  17  is depressurized, and the secondary pressure set at pressure reducer  15  is present in chamber  16 . If wheel  24  strikes a raised area on the ground and is forced upward, the pressure in chamber  16  rises above the secondary pressure of pressure reducer  15 , and hydraulic fluid flows out of chamber  16  via pressure reducer  15 —which functions in this case as a pressure relief valve—and the drain line thereof. In contrast, if a low area in the ground is driven over, hydraulic fluid flows from the pump via directional control valve  14  and pressure reducer  15  back into chamber  16 , and connecting rod extends  23  until it once more supports a weight that corresponds to the product of the cross-sectional area of chamber  16  and the secondary pressure of pressure reducer  15 . 
         [0036]    If front attachment  2  is raised above the working height intended for the harvesting operation, e.g. in the turnaround, while directional control valve  14  is in the position shown in  FIG. 2 , connecting rod  23  extends until it reaches a stop in which the volume of piston-ring side chamber  17  is minimal. If, in this situation, front attachment  2  starts to roll and wheel  24  strikes the ground, connecting rod  23  is forced back against the pressure present in the face-end side chamber  16 , and hydraulic fluid flows out of chamber  16  via a pressure relief valve integrated in pressure reducer  16 , to tank port T. As a result, the rolling motion is braked continuously and without risk of damage to the front attachment. 
         [0037]    Once the rolling motion has come to a standstill, the torsionally elastic design of feed rake  8  enables the front attachment to be rotated back into the equilibrium position thereof. The load on wheel  24  is relieved as a result, and hydraulic fluid can flow from the pump back to chamber  16 . However, the throughput of directional control valve  14  and pressure reducer  15  is limited to such a low value that wheel  24  loses ground contact when the front attachment returns to the equilibrium position. The extension motion of wheel  24  is therefore unable to drive the rolling motion in the opposite direction and cause the other wheel to strike the ground. 
         [0038]    When directional control valve  14  is switched to second position thereof, which is not shown in  FIG. 2 , the pressure at the high-pressure port of pressure reducer  15  diminishes, and non-return valve  21  blocks. If feed rake  8  is now lowered, and all of the weight of front attachment  2  rests on the two wheels  24 , the pressure fluid flows out of chamber  16  via pressure reducer  15  to the tank, and connecting rod  23  is pressed into lifting cylinder  9 . If front attachment  2  is now lifted once more, non-return valve  21  prevents connecting rod  23  from extending again due to the weight of wheel  24  mounted thereon, and therefore front attachment  2  can be lowered easily and safely onto a transport vehicle or a base. 
         [0039]      FIG. 3  shows a schematic illustration of a hydraulic system in which the two lifting cylinders  9 ,  10  are coupled to one another. Components of this hydraulic system that are similar to those of system shown in  FIG. 2  are labelled with the same reference characters and are not explained again. In the configuration shown, directional control valve  14  is open, and the pump pressure is present at the high-pressure port of pressure reducer  15 . The controlled outlet of the pressure reducer is connected to face-end side chamber  16  of lifting cylinder  9 , and so it has the second pressure of pressure reducer  15 . Piston-ring side chamber  17  of the same lifting cylinder  9  communicates via a compensating line  18  with a face-end side chamber  19  of lifting cylinder  10 . A piston-ring side chamber  20  of lifting cylinder  10  is connected, in turn, via switchable non-return valve  21  to a low pressure line  22  leading to the tank of vehicle  1 . 
         [0040]    In the equilibrium state, the weight supported by the two lifting cylinders  9 ,  10  corresponds to the secondary pressure of pressure reducer  15 , multiplied by the cross-sectional area of chamber  19 . Chamber  20  is depressurized, and the pressure in chambers  17 ,  19  automatically sets in according to the distribution of the weight of front attachment  2  on the two rollers  24 . 
         [0041]    If right roller  24  travels over a raised area on the ground, the pressure in chambers  17 ,  19  increases, and if the pressure in chamber  16  then exceeds the set secondary pressure of pressure reducer  15 , hydraulic fluid flows out of chamber  16  via pressure reducer  15  to low pressure line  22 . At the same time, chamber  20  draws hydraulic fluid out of low pressure line  22 . The two lifting cylinders  9 ,  10  therefore yield simultaneously. The diameter of lifting cylinder  9  is greater than that of lifting cylinder  10 , and so the cross sections of chambers  17 , 19  can be made identical, and the lift of the two cylinders  9 ,  10  is identical. The yielding of lifting cylinder  10  under the pressure exerted by the passage over the raised area in the ground therefore does not cause torque to act on front attachment  2 , which could trigger a rolling motion of front attachment  2 ; instead, the supporting force of lifting cylinders  9 ,  10  is merely redistributed onto feed rake  8 . Since the latter supports front attachment  2  at the center of gravity, the supporting force additionally applied by same does not create torque. Instead, front attachment  2  drops only until the return force of the resilient suspension on feed rake  8  has compensated for the increased load. 
         [0042]    In an analogous manner, lifting cylinder  9  is also pressed back upwardly if roller  24  thereof travels over a raised area on the ground. Simultaneously, hydraulic fluid is drawn out of chamber  19  of lifting cylinder  10  and into chamber  17  of lifting cylinder  9 , and therefore lifting cylinder  10  yields. 
         [0043]    If front attachment  2  is raised off of the ground when traveling in a turnaround, the mode of operation of the hydraulic system is substantially the same as that described above. Since only one of the two wheels  24  can have ground contact at any one time during a rolling motion, the total load-carrying capacity of the hydraulic system—which is the product of the secondary pressure of pressure reducer  15  and the cross section of chamber  16 —is available for braking the rolling motion, regardless of which of the two rollers  24  touches the ground. 
         [0044]    According to a development, a sensor  25  can be provided for detecting the vertical position of connecting rod  23  on lifting cylinder  9  or  10 . The measurement signal of sensor  25  can be used to track the height of front attachment  2  over the ground using lifting cylinders of vehicle  1 , which act on front attachment  2  or feed rake  8 . 
         [0045]      FIG. 4  shows an alternative embodiment of the hydraulic system. Lifting cylinders  9 ,  10  are structurally identical to those in the second embodiment and are not described again. In this case, pressure reducer  15  is connected directly to the pump via port P, and a directional control valve  26 —in the position thereof shown in the figure—connects the controlled outlet of pressure reducer  15  to chamber  16  of lifting cylinder  9 . Chambers  17 ,  19  are connected by a compensating line  18 , as in  FIG. 2 , and chamber  20  is connected to tank port T via non-return valve  21  and directional control valve  26 . When directional control valve  26  is in the position shown in  FIG. 4 , lifting cylinders  9 ,  10  behave just as they do in the embodiment shown in  FIG. 3 . In a second position of directional control valve  26 , however, the controlled outlet of pressure reducer  15  is connected to chamber  20  of lifting cylinder  10 , and chamber  16  of lifting cylinder  9  is connected to tank port T. In this position of directional control valve  26 , hydraulic fluid flows from pressure reducer  15  into chamber  20 , and out of chamber  19  into chamber  17 . Connecting rods  23  can therefore be moved into the retracted stop position thereof, without the need to lower front attachment  2  on vehicle  1 . The amount of time required to retract connecting rods  23  is as brief as for the embodiment depicted in  FIG. 2  or  3 . 
         [0046]    The feature common to the embodiments in  FIGS. 3 and 4  is that they can perform their function of suppressing rolling motions of front attachment  2  provided only that high pressure is present at pump port P in order to maintain the secondary pressure at pressure reducer  15 . If connecting rods  23  have yielded when a raised area on the ground is traveled over, then pressurized hydraulic fluid must be supplied in order to restore the previous state. Drive power must be provided for this purpose, which increases the fuel consumption of the working machine. 
         [0047]    By comparison,  FIG. 5  shows a diagram of a hydraulic system according to a fourth embodiment of the invention, which functions even when hydraulic fluid under high pressure is not continuously available. Lifting cylinders  9 ,  10  of this embodiment differ from those shown in  FIGS. 3 and 4  in that the former have identical cross sections. Not only is compensating line  18  provided between piston-ring side chamber  17  of lifting cylinder  9  and face-end side chamber  19  of lifting cylinder  10 , but, conversely, compensating line  27  is also provided between piston-ring side chamber  20  and face-end side chamber  16 . One pressure buffer  28  and  29  is connected to each of the two compensating lines  18 ,  27 . When the hydraulic system is in equilibrium, the pressures in all four chambers  16 ,  17 ,  19 ,  20  are identical, and the supporting force used to support skids  11  or wheels  24  at the lower end of connecting rods  23  on the ground during the harvesting operation is the product of said pressure with the cross section of connecting rods  23 . Due to the coupling via compensating line  18 ,  27 , the two connecting rods  23  yield in the same manner if force acts on one of them that is greater than the above-mentioned supporting force. Due to the uniform retraction motion of the two lifting cylinders  9 ,  10 , the ground drive of vehicle  1  is loaded additionally via feed rake  8  and applies the remaining force required to support front attachment  2  without exerting torque onto front attachment  2 . 
         [0048]    A valve block  30  connects a pump port P and a tank port T selectively to the two compensating lines  18 ,  27 . When the hydraulic system is operating, valve block  30  is completely blocked, and pressure fluid is merely exchanged between chambers  16 ,  20  or  17 ,  19  and particular pressure buffer  28  assigned thereto. If one of the two connecting rods  23  is forced backward during operation, face-end side chambers  16 ,  19  of the two lifting cylinders  9 ,  10  become smaller, and the displaced hydraulic fluid is distributed between piston-ring side chambers  20 ,  17  of the particular other lifting cylinder and pressure buffers  28 ,  29 . As soon as the force acting on the connecting rod diminishes, the two lifting cylinders return to their neutral position, driven by the pressure in buffers  28 ,  29 . 
         [0049]    The extent to which connecting rods  23  are extended in said neutral position depends on the pressure in chambers  16 ,  17  or  19 ,  20 , or on the quantity of hydraulic fluid in the two branches of the system composed of chambers  16 ,  19 , compensating line  18 , and pressure buffer  28  connected thereto, and chambers  16 ,  20 , compensating line  27 , and pressure buffer  29  connected thereto. The greater the quantity of hydraulic fluid is in the system, the further the connecting rods  23  are extended for a given supporting force. The quantity of hydraulic fluid in the two branches of the system must be equal for the two connecting rods  23  to be extended by equal distances in an equilibrium position. To adapt this quantity as necessary, a connection is established in valve block  30  between pump port P or tank port T and one of the compensating lines  18 ,  27 . Sensors  31  are provided to ensure that the two branches contain the same amount of hydraulic fluid. They deliver measured flow rate values which can be integrated to monitor the quantity of hydraulic fluid in each branch. The sensors also deliver measured pressure values which make it possible to determine the volume of the connected branches and, therefore, the position of connecting rods  23 . Instead of flow rate/pressure sensors  31 , position sensors  25  could also be provided, as shown in  FIG. 3 , although in this case one sensor  31  or  25  is required for each lifting cylinder  9  or  10 , because the quantity of hydraulic fluid in the branch comprising chambers  17 ,  19  can change, in contrast to the embodiment depicted in  FIG. 3 . 
         [0050]    When front attachment  2  is lifted off of the ground while chambers  16 ,  17 ,  19 ,  20  are pressurized, connecting rods  23  extend to a stop—as described with reference to the first embodiment—at which the volume of piston-ring side chambers  17 ,  20  is minimal, and therefore all of the freedom of motion of connecting rods  23  is available as a braking path to absorb a rolling motion