Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Patent
1993-08-23
1994-12-20
Nilson, Robert G.
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
G05D 1610
Patent
active
053738659
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an accumulator charging valve, which for the connection of an inlet supplying a hydraulic system to an outlet when an adjustable upper charging pressure in the hydraulic system is reached and for separating this connection when an adjustable lower charging pressure in the hydraulic system is reached, is provided with a control piston, which in one of its two switching positions breaks the connection between the inlet and outlet and in the other switching position makes this connection, a control connection connecting the hydraulic system to the accumulator charging valve being separated from the outlet by means of a separating device.
Accumulator charging valves of this type, which are also known as disconnection valves, are normally used in hydraulic systems or hydraulic circuits, which comprise at least one hydraulic accumulator for keeping the pressure in the hydraulic system constant. The respective hydraulic accumulator in this case operates in a range between a lower and an upper charging pressure, whereof the respective pressure altitude is adjustable, thus can be freely selected. If the lower or the upper charging pressure is not reached or is exceeded, by means of the accumulator charging valve, the connection to the inlet ensuring the hydraulic oil supply is made or broken. The consequently adjustable difference between the lower and the upper charging pressure can be great, but can also adopt very low values.
An accumulator charging valve of the aforementioned general type has already been described in DE-PS 36 08 100. In this known accumulator charging valve, the lowest possible leakage rate within the valve should be achieved, in order to ensure that the respective hydraulic accumulator maintains the pre-set system pressure even over a relatively long period of time. This known accumulator charging valve has a control piston, one part of the piston, constructed as a separating device, in each switching position of the control piston which can be adopted, separating the connection between the control connection and the outlet, which opens into the tank. By way of an annular gap formed by this piston part, a leakage occurs between the control connection and the outlet leading to the tank. Thus the charging pressure in the accumulator is reduced, which causes the drawbacks described in DE-PS 36 08 100.
DE-OS 37 44 178 discloses a different type of embodiment of a hydraulic accumulator charging valve, which comprises a main piston and an anticipatory control supplied by way of a restrictor with pressure medium from the inlet, with an anticipatory control valve constructed as a seated valve, which after the opening achieved at the disconnecting pressure, is held in the open position by an unlocking piston and thus causes the disconnection position of the main piston and secures the latter until a lower connection pressure is reached. Thanks to this construction, at least when the outlet is under load, there is no longer any loss of control oil. For this purpose, a return flow of the fluid from a hydraulic accumulator connected to the accumulator charging valve is prevented by a closed non-return valve, which is located in the main piston, which comprises a stepped annular surface, which with the formation of a hermetically sealing seated valve can be brought into contact with a step located within the housing. Due to this the contents of the hydraulic accumulator can be closed off in a leakage-free manner.
Based on this prior art, it is the object of the invention to provide an accumulator charging valve with freely adjustable switching points, which operates reliably free from oil leakages so that the pressure in the hydraulic accumulator is kept constant even over a relatively long period of time. This object is achieved by an accumulator charging valve with the features of claim 1.
Due to the fact that in the accumulator charging valve according to the invention, with the features of the preamble of claim 1, on reaching the adjustable upper charging pressure, by means of
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patent: 2545712 (1951-03-01), Stevenson
patent: 2737966 (1956-03-01), Lucien
patent: 3024732 (1962-03-01), Nyman
patent: 3329153 (1967-07-01), Henry-Biabaud
patent: 4114637 (1978-09-01), Johnson
patent: 4603708 (1986-08-01), Altmann
Bar Harald
Jung Rudiger
Flutec Fluidtechnische Gerate GmbH
Nilson Robert G.
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