1. Field of the Invention
The invention relates to a directional seat valve comprising a valve body which is arranged in a valve bore and biased against at least one valve seat. It is lifted off the valve seat for connecting a pressure connector to a tank connector or a work connector. The invention furthermore relates to a method for assembling such a directional seat valve.
2. Description of the Related Art
Such directional seat valves have a valve housing with an axial bore in which a valve body is moveably arranged. The valve body is biased by a pressure spring against the valve seat. Upon surpassing a predetermined pressure at the inlet connector, the valve body is lifted off the valve seat and moved into an opening position in which the inlet connector is connected to an outlet connector, for example, a work connector or a tank connector.
In the publication xe2x80x9cDer Hydraulik Trainerxe2x80x9d, vol. 1, Mannesmann Rexrodt GmbH, 1991, p. 203, a directional seat valve is described in which one valve body has correlated therewith two valve seats so that, depending on the position of the valve body, the inlet or pressure connector is connected to a working connector or the working connector is connected to the tank connector. This valve is provided with negative overlap so that in an intermediate position, in which the valve body is resting neither against one nor the other valve seat, all three connectors communicate with one another.
In particular, directional seat valves with smaller nominal diameter are generally directly controlled by a mechanically acting device, for example, a solenoid so that the valve body can be brought into a predetermined switching position or can be maintained in it.
The problem with such directional seat valves is that the magnetic operating point of the solenoid must be adjusted relatively precisely to the axial position of the valve seat so that switching of the solenoid acts without play and without delay onto the valve body.
This means that the components of the mechanical connecting chain between the solenoid and the valve body must be exactly adjusted with respect to their tolerances to the magnetic operating point of the solenoid.
It is therefore an object of the present invention to provide a directional seat valve and a method for assembling the directional seat valve in which the process-technological and assembly-technological expenditures are reduced in comparison to conventional solutions.
In accordance with the present invention, this is achieved for the directional seat valve in that the valve seat is provided on a shaped part which is inserted with press-fit into the valve bore.
The directional seat valve according to the present invention comprises: a valve housing having a pressure connector configured to supply a pressure medium to the valve housing, a tank connector configured to return the pressure medium to a pressure medium tank, and a working connector configured to supply the pressure medium to a working device; a valve bore arranged in the valve housing; one or more shaped parts each configured to be press-fit into the valve bore and each having a valve seat; a valve body arranged in the valve bore and configured to cooperate with the valve seat of the one or more shaped parts for controlling flow of the pressure medium from the pressure connector to at least one of the tank connector and the working connector.
Moreover, in accordance with the present invention, this is achieved in connection with the method in that the first shaped part is press-fit into the valve bore for forming the first valve seat, wherein the press-fit insertion depth is selected depending on the position of the solenoid armature push rod; the valve body is then inserted; and the second shaped part is subsequently press-fit into the valve bore for forming the second valve seat, wherein the press-fit insertion depth is again selected depending on the position of the armature push rod.
The method according to the present invention for assembling a directional seat valve actuated by an armature push rod of a solenoid comprises the steps of: press-fitting a first shaped part with a first valve seat into a valve bore and selecting a press-fit insertion depth in the valve bore based on a position of an armature push rod; inserting a valve body into the valve bore; and press-fitting a second shaped part with a second valve seat into the valve bore and selecting a press-fit insertion depth of the second shaped part in the valve bore based on the position of the armature push rod.
With the directional seat valve according to the invention the valve seat body is realized by a shaped part which is inserted with press-fit into a valve bore of the valve housing. The press-fit insertion depth depends on the actual magnetic operating point of the employed solenoid so that an optimal response of the valve to the switching of the solenoid is ensured. The press-fit insertion depth can be adjusted according to the invention, for example, by suitable tools which are provided with stops determining the press-fit insertion depth. Upon insertion of the shaped parts by means of the tools, the stop of the tools can be brought into contact with the armature push rod. Due to the exact correlation between the magnetic operating point and the position of the valve seat, it is no longer required to provide a linearization of the solenoid used for switching the directional seat valve so that the configuration of the inventive directional seat valve is further simplified.
The inventive configuration of the valve seat in the form of a shaped part inserted with press-fit into the valve bore can be employed especially advantageously for so-called single ball valves in which the valve body is arranged between two valve seats so that, depending on the control action, the three connectors can communicate with one another in a predetermined connecting pattern.
The control action for the valve body is preferably realized by a solenoid. In an especially preferred embodiment, the valve body is biased against one of the valve seats by a push rod of the solenoid that is acted on by a pressure spring. Upon actuation of the solenoid, the push rod is lifted off the valve body against the force of the pressure spring so that the valve body can be moved against the other valve seat.
The manufacture and assembly of the shaped part are especially simple when the shaped part is deep-drawn from sheet metal. The outer diameter of the shaped part, which is expediently cup-shaped, is preferably selected such that it is over-sized relative to the valve bore so that the shaped part can be inserted with press-fit.
The configuration of the valve seat in the shaped part is especially simple when in the bottom of the cup-shaped part an outwardly or inwardly projecting portion is formed which is provided with a penetration forming the valve seat.
Inventively, this valve seat is fine-machined by stamping with a valve body having a diameter that is greater than that of the actually employed valve body so that a precise contact and seat surface for the valve body is provided.
For a single ball valve the valve body is preferably guided by a guide sleeve which is positioned between the two press-fit shaped parts and which prevents a radial deflection of the valve body. In this way, a safe sealing and closure of the valve seat is ensured.
The two shaped parts for a single ball valve are preferably configured such that they can be inserted into the valve bore from one end of the valve housing and have substantially the same orientational position, i.e., are pointed with their cup bottom toward the solenoid. In order to facilitate inflow and outflow through radial connectors of the valve housing, the shaped parts are radially stepped so that the pressure medium flow to the valve seat is facilitated. The push rod of the solenoid is designed preferably such that it penetrates the neighboring valve seat and biases the valve body in the direction toward the other (remote) valve seat.
The valve housing can have an especially compact configuration when the coil member of the solenoid is radially widened toward the valve portion so that a projecting end portion of the valve housing can be inserted into the radially widened portion.
Other advantageous embodiments of the invention will become apparent from the following detailed description.