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GENERAL INFORMATION
he following is a brief explanation of how the concrete
cylinders, hydraulic cylinders, shuttle tube, valves and
hopper work in sequence to pump concrete.
The hydraulic pressure is generated by a variable volume,
pressure compensated, axial piston pump that is driven by
a diesel engine. The rod sides of the drive cylinders are
hydraulically connected together creating a “slave circuit,”
which allows hydraulic oil to transfer from one piston to
the other.
The two part cycling sequence is initiated by an electrical
signal generated by two proximity switches activated by
the drive cylinder. The proximity switches are normally
open, magnetically sensing the movement of the main
drive cylinder. As the drive cylinder piston head passes the
proximity switch, an electrical signal is sent to the solenoid
operated pilot valve which in turn directs pilot oil to the four
valves controlling the drive cylinder and the shuttle cylinder.
A one-gallon accumulator assists the movement of the
shuttle tube. This circuit assures that the shuttle tube will
throw with the same intensity of each stroke regardless of
how fast the main drive cylinders are cycling.
Figure 3. Pumping Cycle 1
TO TANK
HIGH PRESSURE
OIL FROM PUMP
PROXIMITY
SWITCH
HYDRAULIC
CYLINDERS
PISTON
CUP
CONCRETE
CYLINDERS
SHUTTLE
TUBE
SLAVE
OIL
SHUTTLE TUBE MOTION
A
B
Figure 4. Pumping Cycle 2
In the first cycle (Figure 3), hydraulic pressure is applied
to cylinder (B), causing the hydraulic piston, which is
connected to the concrete piston and piston cup, to
discharge concrete into the delivery line.
As one cylinder is discharging concrete, the hydraulic
oil from the rod side (B) of the drive cylinders is being
transferred through the slave circuit causing the opposite
cylinder (A) to move back on the suction stroke, filling the
cylinder with concrete.
The shuttle tube is sequenced to pivot to each concrete
cylinder as the drive cylinders stroke to push concrete. As
the second cycling sequence begins (Figure 4), the shuttle
tube pivots to the opposite cylinder (A).
The hydraulic piston passes under the proximity switch
and sends pressure to the piston, causing it to stroke and
discharge concrete into the delivery line. Hydraulic oil is
transferred through the slave circuit to cylinder B, causing
it to start a suction stroke, refilling it with concrete. The
pumping sequence then repeats for the duration of the
operation.
TO T
ANK
HIGH PRESSURE
OIL FROM PUMP
PROXIMITY
SWITCH
HYDRAULIC
CYLINDERS
PISTON
CUP
CONCRETE
CYLINDERS
SHUTTLE TUBE
SLAVE
OIL
SHUTTLE TUBE MOTION
A
B
B
HYDRAULIC
SHUTTLE
CYLINDER