Hydraulic Circuit Diagram (Dcr-880-H & Dcr-880-H-Hp); Manual Hydraulic System Sequence Of Operation - Vestil DCR-880 Series Instruction Manual

rev. 6/7/2018
Hydraulic Circuit Diagram – DCR-880-H and DCR-880-H-HP
The piston assembly incorporates a two-speed mechanism comprised of five main components:
1. Piston blind-side – Chamber A
2. Rod-side – Chamber B
3. Back-fill check

Manual Hydraulic System Sequence of Operation:

Raising the carriage
The sequence begins with the foot pedal in the neutral ("home") position. The operator activates the hydraulic
system by pressing the foot pedal down. This is referred to as the "power-stroke". After releasing the foot pedal, the
piston return spring (B) exerts an upward force on the piston. Oil flows from the reservoir, through the inlet check
valve, and into chamber A. At the same time, oil trapped in chamber B from a prior cycle flows across the back-fill
check into chamber A. When another power stroke occurs, the inlet check valve closes are prevents oil from flowing
back into the reservoir. The outlet check valve simultaneously opens and oil flows into the cylinder. The piston return
spring forces the piston and the foot pedal back to the home position and chamber A again fills with oil as the piston
rises.
The pump has two modes of operation: 1) Low-pressure, high-volume and 2) High-pressure, low-volume.
1. Low Pressure, High Volume.
When raising an unloaded or lightly loaded platform, the pump operates in low-pressure mode. As the operator
presses the foot pedal (power stroke):
a. Back-fill check remains closed;
b. High / low volume relief poppet remains closed; AND
c. All oil in chamber A flows into the cylinder.
2. High Pressure, Low Volume
When raising a partly loaded or heavily loaded platform, the pump operates in high-pressure mode. During a
power stroke:
a. Back-check remains closed;
b. High / low volume relief poppet opens;
c. A volume of oil equal to the annulus (piston diameter minus the rod diameter) flows from A to B;
d. Oil equal to the cross-sectional area of the rod flows to the cylinder; AND
e. The force required to open the high / low volume relief poppet adds to the cylinder load resistance.
Copyright 2018 Vestil Manufacturing Corp.
Chamber A
The pump assembly consists of 10 primary components:
Oil reservoir
1.
2. Inlet check poppet
3. Pump body
4. Pressure relief valve
5. Outlet check
Chamber B
B
6. Release valve assembly
7. Cylinder
8. Piston return spring
9. Pump pedal
10. Piston rod
4. High-volume / low-volume relief poppet
5. Piston rod
DCR-880, MANUAL
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