HP 13255 Technical Information page 37

132~5
Cartridge Tape Module
13255-91032/35
Rev AUG-Ol-76
assembly has registration surfaces which control the fore and aft
position Of the cartridge. These surfaces are accurate to within
+1-0.001
inch with respect to locatinq pin holes on the base.
Tnes~
holes in turn determine the position of the head bridge assembly.
Side-to-side location of the cartridge, a less critical registration,
is accomplished by maintaining minimum clearance between the cartridge
and the drive.
3.3.1.3 the base assembly also includes a latching and release mechanism wnich
is actuated by a release button. This button is made of green trans-
parent plastiC so that it also acts as a light pipe to bring the light
from an indicator lamp on a circuit board at the rear of the drive to
the surface of the button. This eliminates the cost and complexity of
a separate indicator on the bezel. The cartridge is inserted by push-
ing it in against the spring loaded latch mechanism.
Four rollers provide the locating force. Two rollers press against the
corner of the notch in the cartridge base at about 45 degrees resulting
in an upward force component. The other two rollers press straight up
holding the cartridge against the locating planes in the base. A force
of about 4 pounds Is required to insert the cartridge. The retention
force is over 3 pounds.
Pressing the button releases the latch taking the pressure off the four
rollers and allowing the cartridge to pop out to a detent position for
easy removal. The cartridge Is ejected part way by the motor assembly
swinginQ forward. At this point the ejector rises out of the base and
continues the cartridge motion out to the detent position. In this
manner, the ejection force does not oppose the latching force when the
cartridqe is fully insert~d. The mechanism resets itself dUring the
ejection and is then ready to accept a cartridge again. The detent
action is effected
by
a pawl which is spring loaded against the car-
tridge
by
the same spring that returns the release button.
3.3.2 HEAD BRIDGE ASSEMBLY -
CTU
TRANSPORT ASSEMBLY.
3.3.2.1
lhe head bridge assembly provides the critical reference surfaces
for head-to-tape positioning and provides mounting for the Cartridge
tlectronics PCA.
3.3.2.2
The head bridge assembly has three pads which contact three small areas
on the reference surface of the cartridge. This defines a reference
plane bOth for
th~
cartridge and the drive. The magnetic head is ad-
justed tor both tilt and azimuth with respect to this plane as part of
the manufacturing process. The head itself has a ball socket whiCh
engages a spherical "bump" molded into the plastiC head bridge. Since
the socket is centered on the magnetic gap in the head, the tilt and