Page 18 - SAFAR

•

SPECIFICATION
MfCHANICAL : The main component of the projector mechanism is a d ie-cast
·and ITi'ifchined chassis plate. This is secured to the interior of the die-cast cabinet, or
"blimp" by four bolts floating in rubber bushes. All running components are secured
to the chassis, whereas the amplifier is mounted on the cabinet itself, where it is, to
some degree, protected from the vibration of the mechanism.

The motor is mounted on the chassis plate and carries a pulley on its shaft w hich
drives the projector mechanism proper. This is done by a V-section rubber and fi bre
belt passing round the blower pulley and the shutter flywheel in turn. The blower
.is of the multi-blade centrifugal type and rotates at motor speed, both pulleys being
identical in size. The blower shaft runs on ball-bearings floating on rubber bushes ,
the bushes being recessed into the chassis plate and blower housing respect ivel y
Di rect ion of rotation is such as to produce a down-draught on the lamp radiator sh iel d.
The blower does not blow on the lamp directly as this would produce an uneve n
te m peratu re gradient over the surface of the glass with consequent danger of cracking

T he shutter itself is of robust construction and is mass-balanced to act as a flyw heel
• fo r the camshaft. The shutter is of the normal two-blade type , and flic ker and cover-
blade angles are equal-77°. The shutter shaft extension , which run s in two ball-
bea rings, carries the composite traverse and thrust cam . The flywheel action of the
shutte r, coupled with the compensated cam act ion , gi ves a very smooth picture shift.
The other face of the shutter carries a steel pini on which drives the large fibre gear-
w hee l coupled to the sp rocket and so und d r um: The gear ratio is 12: I, and the
sprocket is a 12-pictu re size. The gearwh eel carries a la rge pu ll ey formin g the drive
for th e spring take-up belt, and recesses in this pulley locate four cone-springs mounted
o n the face of the flywheel. T he gear rotates on th e outside of a sleeve beari ng ,
whereas t he flywheel shaft runs on the inside. Th e flywheel shaft carries the Sf¥ocket
and sound-drum combined . Thus the sprocket is ins ulated from transmission vibrat ion
and the damping introduced by the spring coup ling e nsures t hat sound reprod uction
is smooth and free from ripp le or wow.

The channels in the ciaw body bearing against the cams are parted an d spri ng-
load·ed. T his not only compensates for wear o n both clawbody and cam, but also gives
.a considerable increase in smoothness .of pictu re shift. The claw teeth are harde ned
and precision gro un d as a precau t io n against undercutting by the film, and the tooth-
plate is rivetted to the clawbody; the whole of the claw and cam motion is continu-
o usly lubricated by capillary o ii lines.

The rear slide block on which the clawbody is located is in the form of an eccentric ;
rot ation of this eccentric moves the datum point of movement of the clawbody as a
whole, and this controls the vertical positioning or "framing" of the picture. This
type of framing control offers the distinct advantage in that t he illuminated area on
the screen remains constant and unchanged ; the gate does not have to be moved from
the o ptimum optic path, and the elevation of the projector as a whole does not have
to be altered.

L