Servomech S.p.A.
16.30-40-50.E - Rev. 01 DD (M/Y) 05/19
10
6.2
Wiring of FC electric limit switches
The electric stroke end switches allow to limit the actuator stroke avoiding to exceed the extreme positions
(Lc or La) and reach the mechanical stops and in this way preventing possible damage.
The electric stroke end switches consists of two normally closed miniature electric switches that are fixed on
the actuator housing and operated by cams.
The cams are driven by the acme or ball screw through a
two-stage gear transmission. The first stage consists of a
worm gear with constant ratio. The second stage consists
of a cylindrical straight-tooth gear with ratio that depends
on the maximum actuator stroke. To set up the actual
actuator working stroke, the rod shall be positioned in the
required position (extended actuator or retracted actuator)
and set the position of the relevant cam around the support
tube, turning and fixing it in the right position.
CAM 1 operates the switch FC 1, which corresponds to the
retracted actuator (Lc) stopping position, while CAM 2
operates the switch FC 2, which corresponds to the
extended actuator (La) stopping position.
The entire assembly – switches, cams and cam driving transmission - is inside a sealed box.
The electric stroke end switches must be connected to the electric control circuit as shown in the wiring
diagram on the left to guarantee motor switch off and to prevent damage to the actuator and to the
application equipment. The electric stroke end switches are supplied already wired with a multicore cable
PVC 4×0.75mm
2
, standard length 1.5 m coming out of the box through a cable gland. The standard wiring is
with NC contact, on request the switches are wired for NO contact.
In case an electric signal is required to identify any intermediate position of the push rod (between Lc and
La), in addition to the two switches FC 1 and FC 2 an extra switch FC 3, mounted above the first two and
operated by the relevant CAM 3, can be supplied.
WARNING! The push rod position determined by the switch FC 3 while the push rod is extending is
different from the push rod position determined by the switch FC 3 while the push rod is retracting.
It is therefore necessary to verify the difference between the two positions, by direct check or asking
SERVOMECH, to evaluate the compatibility with the application requirements.
The switch FC 3 is supplied with normally CLOSED contact (NO contact on request) already wired with a
multicore cable 2 × 0.75 mm², standard length 1.5 m. The wire colours are BLUE and BROWN.