Land vehicles – Wheeled – Articulated vehicle
Reexamination Certificate
1999-10-05
2001-03-20
DePumpo, Daniel G. (Department: 3611)
Land vehicles
Wheeled
Articulated vehicle
C172S445000, C172S450000
Reexamination Certificate
active
06203047
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims priority to German Patent Application 198 45 968.8 filed Oct. 6, 1998.
BACKGROUND OF THE INVENTION
The invention relates to a device for stabilizing the two lower steering arms of a tractor. The arms are actuatable by a hydraulically operated power lever. The lever has a side strut per lower steering arm. Each side strut includes a first single-acting hydraulic cylinder. The cylinder has a switching assembly which enables the two first single-acting hydraulic cylinders of the side struts to be connected to the hydraulically operated power lever. The connection has a mechanism for jointly separating the two first single-acting hydraulic cylinders hydraulically from the power lever. Also, a control establishes the connection as soon as a settable pivot position of the lower steering arms has been achieved.
In DE 195 37 555 A1, for example, the supply of the hydraulic cylinders of the side struts takes place in parallel with the supply of the hydraulic power lever. The hydraulic power lever adjusts the lower steering arms. This means that the lower steering arms are centered centrally as a function of the lifting force and position. Stabilization only takes place while the lower steering arms are being lifted. The position switch ensures that, during the lowering operation, the hydraulic cylinders of the side struts and the hydraulic power lever are jointly connected to the return line. When work is carried out on a slope, the resulting downward-directed forces cause the attached implement to assume an inclined position. Furthermore, the lower steering arms cannot be set or cannot be reliably set to the respective dimension of spread. This is due to the fact that the hydraulic cylinders cannot apply an effective force to the lower steering arms while being raised unless an implement is received at the lower steering arms.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the device. Accordingly, when operating the hydraulic power lever, in the raising sense, adjustment and centering of the lower steering arms takes place relative to the longitudinal axis of the tractor. This occurs even in those cases where no implement is received at the lower steering arms.
In accordance with the invention, a control valve is coupled with the connecting line common to the two first single-acting hydraulic cylinders and with a line which leads to a second single-acting hydraulic cylinder associated with the power lever. The control valve has three ports. The first port serves to establish a line connection with the line leading to the second single-acting hydraulic cylinder. The second port provides a connection with the return line leading to the tank. The third port establishes a connection with the connecting line. A first pressure-controlled return valve is in the line leading to a second single-acting hydraulic cylinder behind the line connection with the switching valve. When a pre-determined pressure value is exceeded, the first pressure-control return valve opens in the direction of the second single-acting hydraulic cylinder. The valve closes in the opposite direction. A second return valve is provided in a bypass line leading to the first return valve. The second valve closes in the direction of the second single-acting hydraulic cylinder and opens in the opposite direction. The control valve is designed to assume three switching positions. All ports are disconnected from one another in the first position. The first port is connected to the third port in the second position. The third port is connected to the second port in the third position.
An advantage of this design is that when pressure is applied by the pressure-controlled return valve, a counter pressure builds which is of a sufficiently high pressure in the first single-acting hydraulic cylinders of the side struts to center the lower steering arms. The control valve connects the first single-acting hydraulic cylinders to the pressure source or to the return line. According to a further embodiment of the invention, the first return valve opens at a pressure of ≧10 bar. The counter pressure of at least 10 bar, generated in this way, is sufficient to securely set the lower steering arms.
To ensure that it is possible to separate the two first single-acting hydraulic cylinders jointly from the pressure supply and the return line, the control valve is transferred into the first position. A main switch is incorporated in a control line to actuate the control valve. In the open condition, the control valve is actuated to assume its first position.
Furthermore, a position switch is incorporated in the control line containing the main switch. The position switch closes the power circuit only after the lower steering arms have assumed a pre-determined pivot position. The position switch also ensures that, when a pre-determined pivot position has been exceeded, the control valve is actuated to assume a second position. If, starting from the above-mentioned position, the pre-determined pivot position is not reached or if, when the main switch is closed, it is found that the pre-determined pivot position (distance from the ground) has not been reached, the control valve is actuated to assume a third position.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.
REFERENCES:
patent: 3425715 (1969-02-01), Weitz
patent: 4862971 (1989-09-01), Azzarello et al.
patent: 4865134 (1989-09-01), Rugen et al.
patent: 4909331 (1990-03-01), Defranco
patent: 5361850 (1994-11-01), Muller et al.
patent: 5462303 (1995-10-01), Langen et al.
patent: 5601146 (1997-02-01), Schlegel et al.
patent: 5697454 (1997-12-01), Wilcox et al.
patent: 6089328 (2000-04-01), Moore et al.
patent: 6131937 (2000-10-01), Coenen
patent: 196 11 626 A1 (1997-11-01), None
patent: 195 37 555 C2 (1998-04-01), None
patent: WO 95/20311 (1995-08-01), None
Adamek Wolfgang
Henseler Heinrich
Kirschbaum Kurt
DePumpo Daniel G.
GKN Walterscheid GmbH
Harness & Dickey & Pierce P.L.C.
Shriver J. Allen
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