Fluid handling – Systems – Sequentially closing and opening alternately seating flow...
Reexamination Certificate
2000-04-21
2002-04-23
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Sequentially closing and opening alternately seating flow...
C137S596170
Reexamination Certificate
active
06374857
ABSTRACT:
TECHNICAL FIELD
The present invention relates to valve assemblies and more particularly relates to a valve assembly for controlling a differential pressure.
BACKGROUND OF THE INVENTION
A preferably pneumatic valve assembly of this type which is used especially for controlling the differential pressure in vacuum brake force boosters of automotive vehicle brake systems is disclosed in German published patent application No. 39 43 003. The three-way/three-position directional control valve disclosed in this application has two coaxially arranged sealing seats which cooperate with a sealing surface of an elastic valve member. The first sealing seat which is interposed between the first and the second port in terms of effect is designed on a valve piston that is elastically suspended in a valve housing. The valve piston is axially displaceable in the direction of the valve member by means of an electromagnet. The second sealing seat which is inserted between the second and the third port in terms of effect is provided in the interior of the valve housing. The valve piston houses an actuating sleeve which is arranged coaxially relative to the first sealing seat, is captivated preferably on the valve piston and movable into a force-transmitting connection with the valve member. The prior art valve suffers from the disadvantage of an abrupt rise of the actuating force which is to be produced by the electromagnet in the presence of a predeterminable travel of the valve piston. This abrupt rise of the actuating force is due to the effect of a pressure difference acting on an annular surface on the sealing surface limited by the two sealing seats and exerts an adverse influence on the controllability of a valve of this type. Another shortcoming is the comparatively high magnetic force level which is induced by the above-mentioned abrupt rise in force and requires high current values for the actuation of the electromagnet.
Therefore, an object of the present invention is to provide a valve assembly of the type mentioned hereinabove which operates on a low level of force which is to be produced by an actuator and the controllability of which is ensured without problems. Another objective is that the valve assembly is easy to manufacture in series production and comprises individual components which are inexpensive to make, thereby avoiding complicated manufacturing measures to the extent possible.
According to the present invention, this object is achieved because the sealing seats are arranged axially opposite each other and have equal effective diameters, and because the valve member is arranged between the sealing seats.
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Search Report of the German Patent Office for Application No. 197 31 417.1.
Backe, W.: “Umdruck zur Borsesung—Grundlagen der Pneumatik”,Institute for Hydraulic and Pneumatic Driving and Steering, 7thEdition, 1986, pp. 81-85; photo 5-3.
Continental Teves AG & Co. OHG
Michalsky Gerald A.
Rader & Fishman & Grauer, PLLC
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