Gear pump unit MFE5 for flange-mounting 0,5l/min

Explanation of hydraulic function

Both (ME5, MFE5) types have the same hydraulic function.
Oil is sucked in at S and flows under pressure through the duct in the
direction P. The oil pressure closes valve V and opens valve E3, at the
same time closing valve E1 against spring tension. If air is entrained
(due to low oil level in the reservoir), valve V remains open and diverts
the air or, respectively, the air-oil mixture into the return duct
(see bubble (o) marking in direction R1). Valve C allows oil under
overpressure to flow out into the return duct (see cross (+) marking).
When the unit stops (interval time), spring-loaded valve E1 opens
and valve E3 simultaneously closes. The system pressure at P can
now be released through valve E1 – with the exception of a small
amount of residual pressure determined by valve E2. This pressure
release is required for the piston distributors to function correctly.
The pressure relief process is shown in fig. 4.

Explanation of the structural differences

In the case of model ME5, the long screw plug D1 blocks flanged port
R2 of the return duct. The oil returning from valves V, C and E1 flows
via port R1 through a tube to the separately mounted oil reservoir
(see fig. 1 and 2).
In the case of model MFE5, the short screw plug D2 – unlike D1
with model ME5 – leaves flanged port R2 open. A plug closes off external
port R1. Flanged port R2 of the return duct drains directly into
the reservoir without any connection threads (see fig. 3 and 4