Pub. 1147 - Rev. 7 SEPTEMBER 2004
5
Mechanical Dock Leveler Hydraulic Conversion
See Figure 1 for locations of these features
LIP
The extendible portion of the dock leveler which provides
a bridge from the platform to the bed of the trailer. A
hole is drilled in the lip to allow the insertion of the RITE-
HITE
®
SAFE-T-STRUT
TM
. Additional details on the SAFE-
T-STRUT
TM
are given later in this section.
LIP KEEPERS
The lip keepers provide structural support when the lip is
not on the bed of a trailer. They provide support at dock
end loads for cross traffic and maintain security for the
dock position when not in use.
SUBFRAME
The subframe of the leveler supports the platform and
protects the motor and the hydraulic fluid reservoir.
PLATFORM
The platform, along with the extended lip, provides the
main bridge between the dock and the trailer bed. It is
hinged at the rear of the subframe, and automatically
adjusts with the position of the trailer bed.
RAMP LIFTING CYLINDER
The ramp lifting cylinder is a single acting hydraulic
piston of heavy duty construction grade, non-adjustable,
with a 3-1/2” diameter piston and a 1-1/2” diameter rod.
When the power unit is energized, the cylinder extends,
lifting the platform. When power is removed, the
platforms weight compresses the cylinder, allowing the
entire unit to float onto the bed of a trailer.
POWER UNIT
This is the motor and pump which delivers hydraulic fluid
to the ramp lifting cylinder and lip cylinder. The power
unit package consists of a 3/4 hp electric motor, a 1.4
GPM gear pump, a 1.0 gallon capacity hydraulic fluid
reservoir, and all valving. The hydraulic oil reservoir
contains a top mounting combination breather filter cap.
Hydraulic oil can be added to the system by removing
the cap and pouring oil into the reservoir.
NOTE
When adding oil, use only MIL-H-5606.
SAFETY STOP SYSTEM
The hydraulic system has an emergency flow control
stopping valve (velocity fuse) that prevents the leveler
from “ free-falling” in emergency conditions. The valve is
hard piped in line with the hydraulic oil hose at the ramp
lifting cylinder.
SAFE-T-STRUT
TM
AND BASE
The hydraulic conversion is shipped with the RITE-HITE
®
SAFE-T-STRUT
TM
. This SAFE-T-STRUT
TM
is inserted
through a pre-drilled hole in the lip and then secured by
placing the end of the strut in the SAFE-T-STRUT
TM
base. The SAFE-T-STRUT
TM
increases the level of
safety for workers when installing equipment if
performing routine maintenance, and must be used
every time service is being performed on the unit.
AUTOMATIC RETURN TO DOCK
(ARTD) SYSTEM (OPTIONAL)
The dock leveler will automatically return to dock from
any position if the lip has been fully extended and a truck
leaves the loading dock. As the leveler lip lowers toward
the pendant position, the lip cylinder retracts, moving the
rotary cam assembly backward. The rotary cam contacts
the limit switch, closing the switch, activating the
hydraulic power unit and raising the leveler. As soon as
the lip has lowered to the fully pendant position, the cam
block moves past the limit switch, releasing the switch
and shutting off the hydraulic power unit. The leveler
returns to the stored position with the pendant lip
lowering into the lip supports.
ARTD LIMIT SWITCH (OPTIONAL)
This switch controls the power unit during recycle. The
rotary cam contacts the limit switch, closing the switch,
activating the hydraulic power unit and raising the
leveler. As soon as the lip has lowered to the fully
pendant position, the cam block moves past the limit
switch, releasing the switch and shutting off the hydraulic
power unit.