Power plants – Pressure fluid source and motor – Expansible chamber type volumetric responsive measuring...
Patent
1997-08-01
1999-03-30
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Expansible chamber type volumetric responsive measuring...
F16D 3102
Patent
active
058874291
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a steering system having a displacement unit and a control unit including an inner control piston and an outer control sleeve, wherein both the control piston and the control sleeve include axially and radially extending channels which communicate with each other and with the displacement unit. The channels form a main conduit extending from a supply connection through the displacement unit and a steering cylinder to a return connection, in which main conduit there are disposed an adjustable input throttle between the supply connection and the displacement unit, two adjustable throttles between the displacement unit and the steering cylinder, and an adjustable return throttle between the steering cylinder and the return connection. A first side conduit extends from the main conduit downstream of the adjustable input throttle to the return connection, in which first side conduit there are disposed a first and a second adjustable load signal throttle, and a second side conduit extending from the load signal connection to the first side conduit at the height between the first and the second adjustable load signal throttle. In the neutral position the first adjustable load signal throttle has a positive overlap as compared to the other adjustable throttles. Steering systems of this type are used in mobile installations which include a steering loop and an operating loop wherein both loops have a common supply pump and the steering loop has priority.
Installations of this type consist, on one hand, mainly of a common supply pump and a common flow division control valve as well as of the steering system and steering cylinder, and, on the other hand, of an operating loop. The flow division control valve is spring biased and receives its control signal in form of a so-called load signal from the hydraulic steering system. The flow division control valve regulates its flow cross sections based on the load signal such that the steering loop is assigned a higher priority and supplied with hydraulic oil as needed, whereas the operating loop receives the excess hydraulic oil. It is known that the load signal can be processed statically or dynamically. Due to the fast reaction speed of the dynamic load signal, the latter processing method is becoming more prevalent in practical applications.
A steering system of this type is described, for example, in the German Patent Application P 44 10 693.9 by the applicant. It consists of a displacement unit and a control unit with an inner control piston and an outer control sleeve provided with channels communicating with each other and with the displacement unit. The channels form a main conduit extending from the input connection to the displacement unit, with an adjustable input throttle interposed therebetween, another main conduit containing adjustable throttles and extending from displacement unit to the steering cylinder, and another main conduit including an adjustable return throttle extending from the steering cylinder to the return connection.
The channels furthermore form a first side conduit which extends from the main conduit downstream of the adjustable input throttle to the return connection and includes a first and second adjustable load signal throttle and a constant throttle.
The channels, in addition, form a second side conduit which extends from the load signal connection to the first side conduit and discharges between the first and the second adjustable load signal throttle.
The adjustable input throttle, the adjustable return throttle and the second adjustable load signal throttle close in the same direction. The first adjustable load signal throttle closes in the opposite direction as the aforementioned adjustable throttles.
This steering system is rather sophisticated and has significant advantages. It has, however, the same disadvantages as any other steering system controlled by load signals. When the steering is not operated, the entire load signal flow has to be regarded
REFERENCES:
patent: 4043419 (1977-08-01), Larson et al.
patent: 4620416 (1986-11-01), Yip et al.
patent: 4730544 (1988-03-01), Jorgensen
Bergmann Erhard
Schildmann Manfred
Voss Gerhard
Hydraulik Nord GmbH
Lopez F. Daniel
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