Mannesmann Rexroth Corporation

Mannesmann Rexroth Ag

Heinz Torkler

Norbert Kreth

Werner Peschel

Eugen Hufnagel

In the case of ferries, floating bridges or the like, a bridge support and a ramp forming the connection to the bank are connected to one another pivotably via a pivot point. For adjusting the ramp incline, a differential cylinder is arranged between the bridge support and the ramp in the area of the pivot point. The piston surfaces of the differential cylinder are impinged upon with a pressure that adjusts itself in accordance with the respective loading of the ramp. The pressure in the cylinder chamber on the rod side is a measure of the bending moment in the connecting area of the ramp to the bridge support. A pressure limiting valve, serving as a safety valve, limits the pressure in the cylinder chamber on the rod side and consequently the bending moment in the connecting area of the ramp to the bridge support. The pressure limiting valve is arranged in a line connecting the two cylinder chambers directly to one another. When the pressure limiting valve responds, hydraulic medium is displaced out of the cylinder chamber on the rod side and fed to the cylinder chamber on the head side. Connected to the low-pressure side of the pressure limiting valve is a volume equalization container which provides a volume equalization between the hydraulic medium displaced out of the cylinder chamber on the rod side and the hydraulic medium required by the cylinder chamber on the head side when the pressure limiting valve responds and which takes up pressure medium from the cylinder chamber on the head side not required by the cylinder chamber on the rod side when the ramp is relieved of load. This device is used in the case of ferries, floating bridges or the like in which a bridge support, a ramp and a differential cylinder connected to them form a bending-resistant support.

Device for adjusting ramps

In the neutral position of a directional control valve in which the connection of the constant pump to the consumer is interrupted the entire delivery of the constant pump is led via a bypass valve to the tank. According to the invention the regulating range of the bypass valve is increased by an additional connection which is controlled by a further piston which in the neutral position of the directional control valve is displaced by a weak spring into the open position and thus ensures a pressureless circulation of the pump working medium to the tank.

Bypass valve

A pump supplies via in each case a directional valve with associated pressure balance fluid or pressure medium to a plurality of loads. When the pump power is not sufficient a proportional quantity reduction is achieved at all loads in that the control voltages of the control members for electrical actuation of the directional valves are supplied to a summation stage and the sum voltage is compared in a comparison stage with a limit value corresponding to the maximum pump displacement, whereupon when the limit value is exceeded a control signal is generated with which the stroke of the driven directional valves is reduced.

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Lohr/Main, Germany

Heinz Torkler