1.4 MANUAL OPERATION
The actuator is equipped with a handwheel to operate the valve in the event of a power failure.
The handwheel is easily engaged with the output shaft via the gear train by pulling the hand/
auto clutch lever towards the handwheel at the same time turning the handwheel slowly until
the clutch is engaged.
An automatic device is incorporated which transfers the drive from manual to power
immediately the motor pinion starts to rotate. As the clutch is withdrawn completely from
manual before engaging power drive the operator is ensured complete safety should the
actuator be started during hand operation.
A bevel wheel on the handwheel shaft meshes with a bevel pinion on the bevel shaft which also
carries a hand spur wheel. The motor spur wheel is fitted to a fixed clutch member which is
axially located in the spider and is provided with pawls to disengage the catch levers and dog
teeth to engage the sliding clutch. The sliding clutch is mounted on the splined shaft which
forms the second reduction pinion at the lower end and a journal bearing of the fixed clutch at
the upper end. The sliding clutch is provided with a groove for the hand/auto clutch lever roller
and during power operation is held in engagement with the fixed clutch by the clutch return
spring. The hand/auto clutch lever is fixed to a spindle carried in bearings through the wall of
the main housing to the external clutch handle. One arm of the hand/auto clutch lever carries
the roller and the other arm determines the position of the spring loaded catch levers.
To engage hand operation the clutch lever is pulled approximately 30° towards the handwheel
whilst slowly turning the latter to allow the gear of the sliding clutch member to engage with
the hand spur wheel. Do not attempt to force the lever into the manual position as this should
be easily and smoothly attained. With the lever in the manual position the motor pinion and
motor gear are bypassed for hand operation. By this action, the catch levers, which are clear of
the fixed clutch member pawls during power operation, are allowed to make contact with the
fixed clutch member and the sliding clutch is retained in mesh with the hand spur wheel
against the action of the clutch return spring by slots in the catch lever s engaging the free arm
of the clutch lever. Two catch levers are employed, and two pawls positioned at 180° on the
fixed clutch member in order to ensure that one catch lever engages the clutch lever in the
event of the stationary position of the fixed clutch being such that a pawl is directly in line with
a catch lever.
To return to power operation the motor is energised and during the first rotation of the fixed
clutch member the free arm of the clutch lever is released from the slot(s) of the catch lever(s)
by the action of the pawl(s) striking the catch lever(s). As the clutch lever also carries the roller
which positions the sliding clutch member the latter is disengaged from the hand spur wheel
and engaged with the dog teeth of the fixed clutch by the clutch return spring to immediately
take up the power drive. With the clutch engaged the free arm of the clutch lever maintains the
catch levers clear of the fixed clutch pawls with the hand lever in the power position, i.e.
parallel with the output shaft. Do not attempt to disengage the hand/auto clutch when power
driving. As the sliding clutch is clear of the hand spur wheel before engaging the dog teeth of
the fixed clutch, it is impossible to transmit rotary motion from motor to handwheel.
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