DCB Product Selection
Step 1: To select the correct DCB Series
wrap spring, determine the maximum speed (RPM) at which
the unit
will operate. Next,
determine the load that the output will
need to drive and the system inertia. Click here to download a PDF containing
inertia calculations.
Step
2: Determine the shaft size on which the wrap spring will
be mounted. Once this is determined, the appropriate size
DCB can be determined.
Step
3: Determine
clockwise (CW) or counterclockwise (CCW) rotation, AC or
DC solenoid, number of stops required.
Click
here to download the complete DCB Product Selection Guide in
PDF format (64k). |
Operation
To start motion, the solenoid is pulsed, moving
an actuator arm away from a control collar. This allows the
clutch spring
to wrap (wind) down onto the output assembly while the brake
spring is unwinding, allowing the output to drive. Motion
is stopped when the actuator returns to its rest position,
and the control collar rotates into it. This
forces
the clutch spring to unwind, releasing the input from the
output, and wraps the brake spring down, stopping the output.
The anti-back
and anti-overrun springs are key items in maintaining position
accuracy during operation. Anti-back will not allow the output
to rotate backwards at any time; this eliminates bounce back
when stopped. The anti-overrun allows rotation of the input
in one direction only and also keeps the output from rotating
faster
than the input. The actual stopping position can be adjusted
after installation by moving the splined cam of the control
collar assembly.
The input is a hub
with drilled and tapped holes to allow mounting of sprockets,
gears, sheaves, etc.
The output is
a hollow quill
that mounts onto the customer’s driven shaft. The
plate must be held in place by a loose-fit pin that does
not allow
any side or radial loads that can preload the unit's bearings.
Supers
vs. Standard
All units have three primary sintered iron hubs that are
oil impregnated: input, brake and an internal hub pinned
to the
output shaft. On standard units the oil lubricates the
bearing surfaces
of the input and brake hubs which ride on the output shaft,
whereas the Supers use needle bearings in the input and
brake hubs to
increase the radial bearing load capability. All types
require the oil in the hubs to lubricate the springs. The
Supers
feature hardened steel wear rings on the primary hubs at
the spring
crossover point of the clutch, brake and shaft hubs to
increase life. The
control collar assemblies are glass-reinforced nylon strengthened
by steel or aluminum inserts. The actuators are Delrin® AF
on all models. |
Product
Functions
Start-Stop
Power is removed from solenoid driven actuator, and the control collar cam
is stopped. The clutch spring unwinds, releasing the input, and the brake
spring
winds down on the brake hub and stopping the load. Load is driven by applying
power to
the solenoid. Load can only be driven in one direction. CW and CCW units are
available. |
