Design and function
Vacuum Pumps N 920 APE-W and N 920 APDC-B
12
Translation of original Operating and Installation Instructions, english, KNF 121690-121708 09/19
Function Diaphragm Pump
Fig. 4: Pump head
Diaphragm pumps transfer, compress (depending on pump ver-
sion) and evacuate gases and vapors.
The elastic diaphragm (
4
) is moved up and down by the eccentric
(
5
) and the connection rod (
6
). In the downward stroke it aspirates
the gas to be transferred via the inlet valve (
2
). In the upward
stroke, the diaphragm presses the medium out of the pump head
via the outlet valve (
1
). The transfer chamber (
3
) is hermetically
separated from the pump drive (
7
) by the diaphragm.
Function diaphragm stabilization system
Fig. 5: Function diaphragm stabilization system
An additional diaphragm, the so-called stabilization diaphragm (3),
separates the underside of the working diaphragm from the “crank”
space of the pump (see Fig. 5). The space between the two dia-
phragms, called a vacuum chamber (2), is connected with the suc-
tion side of the pump via an balancing connection (1). This way,
the vacuum chamber has approximately the same pressure as the
working space of the diaphragm pump. The pressure difference
between the upper and underside of the diaphragm approaches
zero. The working diaphragm remains stable, independent of the
inlet pressure of the pump. This improves the suction speed of the
pump significantly, over its entire working range.
1
Outlet valve
2
Inlet valve
3
Transfer chamber
4
Diaphragm
5
Eccentric
6
Connection rod
7
Pump drive
1
Balancing connection for
vacuum chamber
2
Vacuum chamber
3
Stabilization diaphragm
