Clamps the trailing edge of the plate on the drum.
The clamps are on the drum when there is a plate on the drum. They are
attached to the TEC actuator when there is no plate on the drum. Unlike the LECs,
the TECs are not fixed to the drum permanently.
The backbone is attached to the side clamp plates, above the drum roller.
If the backbone has to be disassembled in the field, the nut plates (57-4518)
should be glued into the trailing edge bottom C-channel (57-3439) using a
cyano-acrylate adhesive (crazy glue).
Do not disassemble the TEC backbone without consulting VLF Engineering.
The main components are:
TECs
There are 10 TECs. Each clamp is held to the drum by 3 magnets.
Any clamp–North or South–can go in any clamp position on VLF
engines because flux interactions between North and South clamps are not
required for proper operation. New engines use only North clamps. Early
engines have both North and South clamps.
Clamp reed switches detect the presence of each clamp on the
backbone. Two 1/4" sensing magnets of opposing polarity are glued
into each TEC directly under the backbone reed switch that senses them.
Park bars
Mounted on the drum just below the LECs, used to align the TECs on
the drum. The TECs are pushed against the park bars when placed on the
drum manually. There are 3 park bars. Each one is a ½ round rod made of
Delrin or Nylatron.
Locking bar
Slides back and forth inside the TEC backbone to lock the clamps to
the backbone. The clamps are locked to the backbone when the locking
pins (mushrooms) on the locking bar are inserted in the narrow part of
the clamp keyholes. The clamps are unlocked when the locking pins are in
the wide opening of the keyholes.
A 3/4" x 1/2" pneumatic cylinder located at the encoder
end of the locking bar actuates the locking bar.
Hall effect sensors mounted at either end of the cylinder detect the
position of the locking bar cylinder piston.
Clamp plate assemblies
Mounted at either end of the engine frame, support the backbones.
Cam followers on the backbone ends roll on nickel-plated angles attached
to the side plates.
The setup is the same as for all backbones. Note that the backbones
do not slide in grooves as with the 3244 engine.
Backbone pneumatic cylinders
Roller backbone: 55-0281 (2.5" x 1¼") Round body used on
VBI to V48 & B1 to B120
Roller backbone: 55-0649 (1.5" x 1.5") Square body used on
V49+, B121+
TEC backbone: 55-0282 (3" x 2¼")
LEC backbone: 55-0281 (2.5" x 1¼") VLF Platesetter only
Actuate the TEC, LEC, and roller backbones.
One cylinder on each clamp plate assembly. Attached to the backbone
by rod ends. For VLF Trendsetters that are upgraded for the film option,
the roller cylinder must be replaced with 55-0649 for machines B121.
Backbone reed switches
Detect the extend and retract position of the backbone. The setup is
the same as for all backbones.
For each backbone, 1 magnet at each end of the backbone, and 2
sensors on the clamp plate assembly.
Each magnet is attached to the backbone by a bracket. The brackets
are slotted axial to the drum, and the magnets are slotted perpendicular
to the plane of the backbone. The sensors are attached to the clamp
plate assemblies. They are slotted roughly in the direction of the
cylinder actuation.
Rod end bearing block
Allows the axial float of the backbone to compensate for the rigid
trunion cylinder mounting and the thermal expansion differences between
the backbone and the aluminum engine frame.
