Directional seat valve Bosch Rexroth art. R901138718

3/2 directional seat valve
General information:
The directional valve of type .-SE..6X is a directional seat valve with solenoid actuation. It controls start, stop and direction of flow. It basically comprises a housing (1), the solenoid (2), the hardened valve system (3) and the balls (4.1 and 4.2) as closing element.
Basic principle:
In the initial position, the ball (4.1) is pressed onto the seat by the spring (7), in spool position, the ball (4.2) is pressed onto the seat by the solenoid (2). The force of solenoid (2) acts via the ball (5) on the actuating plunger (6) that is sealed on two sides. The chamber between the two sealing elements is connected to port P. Therefore, the valve system (3) is pressure-compensated in relation to the actuating forces (solenoid or return spring). This means that the valves can be used up to 420 bar.
Notes

• 3/2-directional seat valves feature “negative spool overlap”. Therefore, port T must always be connected. That means that during the switching process – from the starting of the opening of one valve seat to the closing of the other valve seat – ports P–A–T are connected with each other. However, this process takes place within such a short time that it is irrelevant in nearly all cases of use.

• The manual override (10) allows for the switching of the valve without solenoid energization.

• It is to be ensured that the maximum flow indicated is not exceeded! If applicable, a throttle insert for flow limitation is to be used (see table “Throttle insert, check valve insert”).

• In order to switch the valve safely or maintain its spool position, the pressure situation must be as follows: P ≥ A ≥ T (for design reasons).

• The ports P, A and T (3/2 directional seat valve) are clearly determined according to their respective tasks. They must not be exchanged or closed. The flow is only admissible in the direction of arrow!

Example: Type .-3SE 6 C6X/420BG12-12NX.Z2/V
4/2 directional seat valve
With a sandwich plate, the Plus-1 plate, under the 3/2 directional seat valve, the function of a 4/2 directional seat valve is achieved.
Function of the Plus-1 plate:
Initial position:
The main valve is not operated. The spring (7) holds the ball (4.1) on the seat (11). Port P is blocked and A is connected to T. Apart from that, one control line is connected from A to the large area of the control spool (12), which is thus unloaded to the tank. The pressure applied via P now pushes the ball (13) onto the seat (14). Now, P is connected to B, and A to T.
Transition position:
Upon actuation of the main valve, the control spool (8) is shifted against the spring (7) and the ball (4.2) is pressed onto the seat (15). During this, port T is blocked, while P, A, and B are briefly connected to each other.
Spool position:
P is connected to A. As the pump pressure acts via A on the large area of the control spool (12), the ball (13) is pressed onto the seat (16). Thus, B is connected to T, and P to A. The ball (13) in the Plus-1 plate has a “positive spool overlap”.

If the annulus area of differential cylinders is not connected to port A, a pressure peak is created in port B during the switching process, which may exceed the maximum operating pressure over the permissible limit.
Example: Type .-4SE 6 Y6X/420BG12-12NX.Z2/V
Throttle insert, check valve insert