Earth working – Mast type hitch – With auxiliary vertical adjustment
Reexamination Certificate
2000-01-07
2001-07-03
Batson, Victor (Department: 3671)
Earth working
Mast type hitch
With auxiliary vertical adjustment
C172S002000, C091S527000, C091S530000, C091S419000
Reexamination Certificate
active
06253859
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority upon German application 199 00 570.2 filed Jan. 9, 1999 and German application 199 39 967.0 filed Aug. 23, 1999, both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a lifting device for the lower steering arms of an attaching device of a tractor or self-driving implement.
Tractors, or self-driving implements, at their rear or, optionally, also at their front, include an attaching device. The attaching device has lower steering arms which are offset in the direction opposite to the longitudinal axis of the tractor or self-driving implement. One end of the lower steering arms is articulatable. It is attached at the rear and/or front to be pivotable around a substantially horizontal axis. In addition, a slight lateral pivotability exists. At their free ends, the lower steering arms includes couplings to connect with an implement. A lifting device is provided to pivot the lower steering arms. The lifting device, which carries an implement attached to the lower steering arms, raises or lowers the implement relative to the ground. Furthermore, as a function of the implement to be attached and the type of application, the lifting device must enable the lower steering arms, to a certain extent, to move freely sideways to a certain extent. In other applications, free pivotability in the vertical direction is essential. In particular, some types of lifting devices which are integrated into the tractor or the implement and include two parallel lifting arms, are connected to the ends of a lifting shaft. The lifting shaft itself is pivoted by a drive. Thus, the lifting arms move in a circular arch. Lifting struts, which are connected to the lower steering arms, are secured to the ends of the lifting arms. In addition, the lifting shaft ensures synchronization of the two lifting arms. A precision adjustment mechanism is arranged at the rear of the lifting device to improve adaptability. The adjustment mechanism adjusts the length of the lifting struts. Furthermore, an assembly is provided which optionally enables a rigid connection with the lower steering arm or disconnection and free vertical mobility. The assembly enables a vertical floating path for yawing the implement. The assembly compensates for transverse inclinations in order to enable tension-free operation.
In the case of a lifting device attached to the front of the tractor or implement, the lower steering arms are normally connected to one another to form a rocker. The drive is in the form of two hydraulic lifting struts. The struts are connected directly to the lower steering arms. An oblong hole in the coupling element is provided to compensate for vertical degrees of freedom in transverse inclinations.
Such an assembly is described in WO 96/03024. The two hydraulic lifting struts can be connected by a common hydraulic line to a pump or to a pressure supply source. This means that the pressure level is the same for both hydraulic lifting struts. Thus, they are both supplied with the same amount of pressure.
Although the above-described types of lifting devices have different designs, they have a common characteristic. The synchronous movements of the two lower steering arms is ensured and a vertical degree of freedom is available. The hydraulic lifting struts are disadvantageous because accurate uniform operation is not ensured due to leakages which can lead to different settings in spite of identical pressure levels.
SUMMARY OF THE INVENTION
It is an object of the present invention to simplify the design of the lifting device. Also, the invention ensures accurate synchronization with respect to adjustment and, finally, it provides further adjustment possibilities.
In accordance with the invention, a lifting device is provided for the lower steering arms of an attaching device of a tractor. The lower steering arms, at one end, are pivotably attached to the tractor. The lifting device comprises, per lower steering arm, a position recording device. The position recording device generates a position signal which represents the respective pivot position of the lower steering arm. A hydraulically loadable, double-acting piston-cylinder unit is provided per lower steering arm. At one end, the cylinder is attached to the tractor. At its other end, the cylinder acts either directly or indirectly, via an intermediate lever drive, on the lower steering arm. The cylinder includes a cylinder chamber at the piston end and a cylinder chamber at the piston rod end.
A switching circuit is provided per piston-cylinder unit. The switching circuit has a directional valve with four ports. The directional valve can be transferred into at least three switching positions. Two ports serve to connect to the piston-cylinder unit. The first port is connected to the cylinder chamber at the piston end. The second portion is connected to the cylinder chamber at the piston rod end. The third port serves to connect to a pressure agent supply source. The fourth port serves to connect to a return line.
In a first position of the directional valve, all ports of the directional valve are blocked. In a second position, the cylinder chamber at the piston end is connected to the pressure agent supply source. Also, in the second position, the cylinder chamber at the piston rod end is connected to the return line. In a the third position, the cylinder chamber at the piston rod end is connected to the pressure agent supply source. Also, in the third position, the cylinder chamber at the piston end is connected to the return line. The switching circuit has an electric switching unit provided with an input to introduce a guiding value corresponding to the nominal position of the lower steering arm. An input for introducing a position signal comes from the position recording device which represents the respective position of the lower steering arm. A comparator compares the guiding value with the position signal. The switching unit, as a function of the result of the comparison, causes the directional valve to assume one of the at least three positions.
An advantage of this embodiment is that while the design has been simplified, additional functions have been provided. Furthermore, accurate setting is ensured because the respective actual position of the lower steering arms is compared with a predetermined nominal position. Any adjustment that takes place is aimed at the nominal position. Thus, both lower steering arms assume the same or the predetermined position. In addition, by being able to control the piston-cylinder units individually, it is possible to set the two lower steering arms independently of one another. This enables compensation for any transverse inclination.
According to a further embodiment of the invention, a fourth switching position is provided in the directional valve per lower steering arm. Here, both the cylinder chamber at the piston end and the cylinder chamber at the piston rod end are connected to the return pipe. For example, if the piston-cylinder units are switched to “return”, the length of the piston-cylinder units can set itself freely and the implement can also be uncoupled in a force-free way. Furthermore, it is possible to set the floating path without the operative having to leave the driver's seat, which is the case with mechanical solutions. To permit synchronization of the lower steering arms, identical or different guiding values are fed into the two switching units.
To complement the solution in accordance with the invention, a selector switch is provided which enables the selection of different operating modes and which acts on both switching units. The two switching units can thus be preprogrammed in such a way that the two lower steering arms are either controlled in accordance with the same guiding value or different guiding values. Furthermore, the two switching units are connected to a common selector switch. Thus, the switching units may be programmed to transfer one directional valve for
Batson Victor
GKN Walterscheid GmbH
Harness & Dickey & Pierce P.L.C.
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