Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1996-07-29
1997-07-15
Ferensic, Denise L.
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
13761419, F16K 3112
Patent
active
056473940
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a control valve having a housing which has an input port and an output port that are connected to one another by a flow path in which a throttling device is arranged.
U.S. Pat. No. 4,858, 222 discloses a control valve which is arranged between a directional valve and a hydraulic motor. Both the inlet line and the discharge line of the motor pass through the control valve. Using two movable sliders and a common counterpressure spring, the attached motor is controlled so that its speed is kept constant irrespective of the loading of the motor.
Furthermore, U.S. Pat. No. 4, 422, 470 discloses a compensating valve provided between a pump and a control valve. The compensating valve is controlled by a spring and a measurement signal which originates from the pressure at a point between the control valve and a work apparatus connected thereto.
The present invention is intended to provide a control valve which is able to hold a volume flow constant irrespective of the load pressure for a connected load.
In the case of a control valve of the kind mentioned in the introduction, this problem is solved in that the throttling device comprises a series connection of a first throttle, the passage of which is externally adjustable, and a second throttle, the passage of which is adjustable in dependence on pressure.
An area of application for such a control valve comprises, for example, controlling the speed of a hydraulic motor which it is desirable to keep constant irrespective of the loading of the motor.
The speed is now determined using the externally, in particular, manually, controllable first throttle. The second throttle, the passage of which, that is to say, the flow cross-section of which, is adjustable in dependence on pressure, responds to pressure changes at the output port that correspond to the loading of the connected load, so that when the pressure at the output port is relatively large, the second throttle opens wider. With an unchanged volume flow, the pressure drop across the second throttle consequently decreases, and the load can be operated at the correspondingly higher pressure. Conversely, if the pressure at the output port drops, the passage or the flow cross-section of the second throttle is reduced, so that with an otherwise unchanged volume flow a larger pressure drop is effected. The load accordingly also receives only a relatively low pressure. Because adjustment of the passage is effected in dependence on pressure, a control loop which operates without further external control elements or signals can be built up here.
It is here preferable for the second throttle to comprise an adjusting element which is urged in the opening direction by an opening pressure dependent on the output pressure and by a spring, and is urged in the closing direction by a closing pressure dependent on the input pressure. When the output pressure prevailing in the output port rises because of a higher loading of the load, a correspondingly larger opening pressure acts in the opening direction on the adjusting element, so that the passage of the second throttle is enlarged. The volume flow can remain the same since the pressure drop it produces at the second throttle is smaller. Conversely, the adjusting element is moved in the closing direction when the output pressure in the output port drops.
The adjusting element is preferably arranged in the housing with a freedom of movement which allows a throttled through-flow of hydraulic fluid from the input port past the adjusting element to the output port. This through-flow forms a film of fluid between the adjusting element and the housing, which enables very low-friction movement of the adjusting element in the housing. Adjustment of the position of the adjusting element is therefore effected exclusively as a function of pressure, because in practice no frictional forces have to be overcome. The gap between the adjusting element and the housing forms, as it were, an auxiliary throttle, at which the normal pressure drop between input port and o
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patent: 2309773 (1943-02-01), Kaufman
patent: 2623331 (1952-12-01), Greening
patent: 3428080 (1969-02-01), Brown
patent: 3534769 (1970-10-01), Leveque
patent: 3677288 (1972-07-01), Martin
patent: 4449548 (1984-05-01), Tutherly
patent: 5190075 (1993-03-01), Tentler
Plauborg Erik
Valbj.o slashed.rn Anders
Zenker Siegfried
Danfoss A/S
Farid Ramyar M.
Ferensic Denise L.
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