Gradall 534B (9020-7317) Service Manual - Manual (Page 95)

When the control lever for the crowd action is
activated, the 2nd and 3rd boom sections move in
and out equally.
Power to move the booms in and out come from a
hydraulic cylinder which is located under the main
Ist boom section. It moves the 2nd boom section. As
the 2nd boom section moves in or out a
combination of a push assembly and sheaves and
cables move the 3rd boom section. The push beam
assembly is fastened to the 2nd boom section at the
rear sheave pin and moves with it.
Two cables are used. The top one is bolted to the
rear of the main boom and runs forward around the
push beam front sheave and back to the anchor
point at the bottom rear of the 3rd boom section.
The lower cable is anchored near the front bottom
of the main boom and passes back around the rear
sheave and is anchored at point (H) of the 3rd boom
section. As the 2nd boom section moves out, forcing
the push beam and sheaves with it, the top cable has
to move forward at point (H) taking the 3rd boom
section with it.
When retracting the booms, the 2nd section moves
in, forcing the lower cable to pull at point (H) and
the 3rd boom section moves in.
GRADALL LOED MATERIALS HANDLER 534B SYSTEM OPERATION
BOOM CROWD (IN-OUT) MOVEMENT
MANUAL “QUICK-SWITCH” ASSEMBLY
A manual, lever operated “Quick-Switch” Assembly
is used at the front of the boom head to attach the
fork and carriage, truss boom or material bucket.
To engage the attachment a button is depressed and
a locking pin (A) removed. Raising the lever moves
the engaging plunger (B) up. Lowering the lever
moves the plunger down.
THREE SECTION BOOM (RETRACTED)
THREE SECTION BOOM (PARTIALLY EXTENDED)
19