Vestil EH-75-50 handleiding
Handleiding
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TABLE OF CONTENTS 5/12/2022 EH MANUAL
TABLE OF CONTENTS Copyright 2022 Vestil Manufacturing Page 11 of 19
Electrical System Operation
The electric circuit consists of a push-and-hold motor start circuit with thermal protection. The timer
circuit activates and runs the motor for approximately 10 seconds. The timer is actuated by either a limit
switch in automatic mode, or by pressing the RESET button in manual mode.
Hydraulic Circuit Sequence of Operation, EH Series [Numbers in Parentheses () Correspond to Numbers in
the Diagram Above]
EH-series dock levelers are hydraulically powered through a sequence of steps. The pressure required to
raise the deck varies with deck size. However, the pressure always remains below the pressure setting of
the lip sequence valve (6). The sequence valve is factory set to 700 PSI, unless the deck’s weight requires
a different setting, and should not be changed.
Pressing the “RAISE” button activates the pump. Oil pressure increases until it equals the cracking
pressure of the outlet check valve (3). The pressure closes valve (4), a pilot-to-close check valve with a 3:1
ratio. When the pilot pressure exceeds one third of the inlet pressure, the valve closes. As pressure builds in
the deck cylinder, the deck rises and the lip rotates outward. When the pressure exceeds 40 PSI, the lip’s
dump valve, (5), closes. The dump valve is a normally open “pilot-to-close” directional valve.
As the lip rotates outward, oil from the cap end of the lip cylinder (12) is forced across the lip relief valve
(2B). The pressure setting of the lip relief valve divides oil flow between the deck cylinder (11) and the lip
cylinder (12), and controls the lip’s movement. If the pressure is too low, the lip will not fully extend. If
pressure is too high, the lip will retract too slowly and fail to return to its stowed position. The lip should
completely rotate outward when the deck rises approximately 18 inches.
After the deck cylinder fully extends, hydraulic pressure continues to increase until the lip sequence
valve (6) shifts. When the valve shifts, there is pressure on both sides of the lip cylinder. Because there is
more pressure applied to the cap end of the cylinder than to the rod end, the lip cylinder retracts.
Releasing the RAISE button deactivates the pump and the hydraulic pressure declines. When the pump
output pressure drops below one third of the lift pressure, the pilot-to-close check valve (4) opens and the
deck begins to descend. A pressure-compensated flow control valve (9) controls the deck’s rate of
descent. Pressure continues to decrease after the deck returns to its fully lowered position. When the
pressure drops below 40 PSI, the lip dump valve (5) opens and allows the lip to return to its stowed position.
The hydraulic system includes a safety device, called a velocity fuse, which prevents the deck from
collapsing if system pressure suddenly drops (for example, if the flow control valve fails or a hose is
punctured). The fuse is integrated into the cylinder. When the fuse closes oil cannot flow back to the
reservoir.
Figure 4: Hydraulic circuit diagram
Bekijk gratis de handleiding van Vestil EH-75-50, stel vragen en lees de antwoorden op veelvoorkomende problemen, of gebruik onze assistent om sneller informatie in de handleiding te vinden of uitleg te krijgen over specifieke functies.
Productinformatie
| Merk | Vestil |
| Model | EH-75-50 |
| Categorie | Niet gecategoriseerd |
| Taal | Nederlands |
| Grootte | 4662 MB |
