Manitowoc Grove YB5515 Service Manual

11-31
5540F/YB5515 SERVICE MANUAL STRUCTURALS
11
braking takes place in the brake valve and that little, if any,
heat is absorbed by the friction brake.
The friction brake is load holding brake only, and has nothing
to do with dynamic braking or rate of descent of a load.
The brake clutch is splined to the primary sun gearshaft
between the motor and the primary sun gear.It will allow this
shaft to turn freely in the direction to raise a load and lock up
to force the brake discs to turn with the shaft in the direction
to lower a load. See Figure 11-58 and 11-59.
The hydraulic cylinder, when pressurized will release the
spring pressure on the brake disc, allowing the brake discs to
turn freely.
Dual Brake System - Operation
When hoisting a load, the brake clutch, which connects the
motor shaft to the primary sun gear, allows free rotation. The
sprag cams lay over and permit the inner race to turn free of
the outer race (Figure 11-58). The friction brake remains fully
engaged. The winch, in raising a load, is not affected by any
braking action. See Figure 11-54.
When the lifting operation is stopped, the load attempts to
turn the primary sun gear in the opposite direction. The
reverse input causes the sprag cams to instantly roll forward
and firmly lock the shaft to the fully engaged friction brake
(Figure 11-59).
When the which is powered in reverse, to lower the load, the
motor cannot rotate until sufficient pilot pressure is present to
open the brake valve See Figure 11-56 and 11-57. The
friction bake within the winch will completely release at a
pressure lower than that required to open the brake valve.
The extent to which the brake valve opens will determine the
amount of oil that can flow through it, and the speed at which
the load will be lowered. Increasing the flow of oil to the
winch motor will cause the pressure to rise and the opening
in the brake valve to enlarge, speeding up the decent of the
load. Decreasing this flow causes the pressure to lower and
the opening in the brake valve to decrease, thus slowing the
descent of the load.
When the main control valve is shifted to neutral, the
pressure will drop and the brake valve will close, stopping
the load. The friction brake will engage and hold the load
after the brake valve closes.
FIGURE 11-58
a2209
FIGURE 11-59
a2210
Reference Only

Manitowoc Grove YB5515 Specifications

General

Brand	Manitowoc
Model	Grove YB5515
Category	Construction Equipment
Language	English