Fluid handling – With indicator – register – recorder – alarm or inspection means
Reexamination Certificate
2000-05-25
2001-07-24
Buiz, Michael Powell (Department: 3753)
Fluid handling
With indicator, register, recorder, alarm or inspection means
C137S596170, C137S627500, C073S168000, C324S418000
Reexamination Certificate
active
06263913
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a type of generally known hydraulic multiway valve having a control piston (main piston) that is displaceable against the force of a spring (main spring), by the plunger of a magnet, from its first position (closing position) to its second position (opening position).
In the case of this known valve, a pressure chamber, in which a pump connection terminates, is closed in the one position of the valve piston (closing position), and a consumer chamber with a consumer are opened toward a return flow chamber and a reservoir connection, so that the consumer is relieved from pressure. In the opening position, the consumer connects to the pump connection, and the pressure chamber is closed toward the return flow chamber and the reservoir.
This valve is especially suitable as a servovalve for a hydraulic valve, which is hydraulically operated.
It is an object of the present invention to improve this known valve such that it is suited for a servovalve with a small overall size, and so that is has a positive cover with respect to closing the consumer chamber toward the return flow and opening the consumer chamber toward the pressure chamber.
SUMMARY OF THE INVENTION
The above and other objects are of the present invention are provided by a hydraulic multiway valve that includes a housing defining a consumer chamber, a return flow chamber, and pressure chamber positioned between the consumer chamber and the return flow chamber. The housing further defines a pump channel open to the pressure chamber, a consumer channel open to the consumer chamber, and a reservoir channel for being opened to the return flow chamber. A main piston is moveably positioned in the housing. The main piston has opposite ends arranged so that the consumer chamber and the return flow chamber are arranged at the opposite ends of the main piston. The main piston defines a central channel that extends through the main piston and is open at the opposite ends of the main piston, so that the consumer chamber and the return flow chamber are capable of being opened to one another via the central channel while the central is open. A spring biases the main piston toward a closed position in which the pressure chamber is closed to the consumer chamber. A plunger piston is positioned in the valve housing for coaxial movement relative to the main piston. The plunger piston is moveable toward the main piston so that a seat end of the plunger piston engages a predetermined one of the ends of the main piston to close the central channel. The plunger piston is moveable away from the main piston to an open position in which the central channel is open. A magnet assembly moves the plunger piston so that the seat end thereof moves into contact with the predetermined end of the main piston to close the central channel. Thereafter, the magnet assembly further moves the plunger piston so that the force of the spring associated with the main piston is overcome so that the main piston is moved to an open position. In the open position of the main piston of the pressure chamber is open to the consumer chamber.
The above-described valve of the present invention has the advantage that the valve housing need not provide connections between the return flow channel and the consumer channel. Consequently, the valve can be accommodated in particular in a valve cartridge. This provides for easy adjusting of the cover and the opening width of the connection between the consumer and the return flow, so that it is possible to adjust in this way the damping of the motion of the main valve.
To avoid that the hydraulic forces are inadequate to raise the plunger piston with certainty from the main piston and to establish the return flow connection between the consumer connection (control connection of the main valve) and the return flow, a safety spring pushes the plunger piston against the force of the magnet assembly to its opening position in such a manner that the center channel is opened in the closing position of the main piston.
In accordance with one aspect of the present invention, the valve housing has a seat that is in the shape of an inner cone. Similarly, the main piston has a flange that is in the shape of an outer cone and that engages the seat of the valve housing while the main piston is in its closed position, so that the pump channel and the pressure chamber are closed with respect to the consumer chamber and the consumer channel. This aspect provides for a reliable, leakproof closure between the pressure chamber and the consumer chamber.
In accordance with one aspect of the present invention, the housing is an inner housing and the hydraulic multiway valve further comprises an outer housing having a front side that mounts the magnet assembly. The inner housing is removably positioned in the outer housing and oriented so that the consumer chamber is proximate the front side of the outer housing. Most preferably, the inner housing is screwably engaged to the outer housing. The plunger piston contacts either the outer housing or a portion of the magnet assembly while the plunger position is in its opened position. The manufacturing advantages of this aspect combine with a satisfactory possibility of adjusting the cover and the opening width of the connection between the consumer and the return flow.
Preferably, the closing end of the main piston, which extends into the consumer chamber, and the seat end of the plunger piston are designed and constructed as a pairing of cones.
The spring and the seating surfaces of the valve housing and the main piston are advantageously constructed so that the pressure chamber can be tightly closed toward the consumer chamber and the control connection. Hydraulic multiway valves, which are used as servovalves, and which are electromagnetically controlled, must offer a high safety standard in many fields of application (for example, in the case of lifting apparatus or in mining).
The construction and further development of an electrohydraulic multiway valve according to another aspect of the present invention has the advantage that errors of the magnet assembly or the valve are recognized immediately and with foresight. To this end, a power control unit is integrated in the activation device of the magnet. The power control unit is preferably located on or in the region of the magnet. The power control unit possesses an electronic memory. The memory stores characteristic values, which characterize in the ideal case the power input of the magnet in the course of switching, when it connects to one of the switch positions. The actual flow of the current taken by the magnet is measured, when the valve is switched to the switch position, and/or when the magnet is disconnected, and at least prominent points of the actual flow or the entire actual flow are compared with the corresponding points of the desired flow or with the desired flow and predetermined deviations are signaled. The signaling of the error message occurs on the valve itself, in particular by an optical signal.
In accordance with one aspect of the present invention, the power control unit functions such that not each deviation is signaled. Rather, it is determined first by test which deviations are within the scope of acceptable operational tolerances.
It is essential for the operation of a servovalve that on the one hand adequate holding forces act upon the valve piston for purposes of positioning the piston safely in its approached switch position. On the other hand, however, it is intended to minimize power consumption. In the case of an electrohydraulic servovalve or multiway valve and in accordance with one aspect of the present invention, this is accomplished through operation of the power control unit. More specifically, the power control unit measures the current flow of the magnet during the switching operation and determines the reaching of the switch position. After a drop of the current at the end of the switching operation, the current is one more time increased substanti
Alston & Bird LLP
Buiz Michael Powell
Krishnamurthy Ramesh
Tiefenbach Bergbautechnik GmbH
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