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3

Hydraulic Circuit & Component Operation

To raise the deck of the table, press the 

"RAISE"

 button of the hand controller. This opens the air motor 

supply valve and flowing air turns the hydraulic pump. Oil from the reservoir moves through the suction filter 

and into the pump. From the pump, pressurized oil flows through the check valve and then enters the 

cylinders.

The function of the check valve is to 

restrict 

oil flow 

to

 one direction, i.e. towards the cylinders. It 

prevents oil

 from flowing

 back into the pump circuit when the pump stops running. This 

trap

s oil in the 

cylinders and maintains the desired elevation

 of the deck

.

If the 

weight of a 

load

 on the table

 exce

eds the capacity of your table

then 

a

lthough

 the 

"RAISE"

 

button 

might be

 pressed 

the deck cannot ascend. Instead, 

pressure

 

build

s

 in the circuit between the pump 

and the cylinders. This

 pressure

 

caus

es the "ball" 

(

or "poppet"

)

 in the relief valve to unseat 

and directs

 the 

pump output

 to

 the reservoir through the return pipe

 rather than to the cylinders.

T

o lower the 

deck

, press the 

"LOWER"

 

control 

button. This opens a hydraulic

 dump 

valve. The 

poppet in the solenoid valve unseat

and oil 

flow

s from the cylinders through the flow control valve, return 

filter, solenoid valve, 

and the 

oil return pipe

 to

 the reservoir.

The flow control valve controls the lowering speed of the table.  It is preset and cannot be changed.
Releasing the 

"LOWER"

 control 

button 

deenergize

s

 the solenoid

 and

 clos

es

 the valve poppet.  This 

prevents oil from returning to the reservoir and 

consequently 

the cylinders stop retracting.  The 

deck

 will 

maintain 

its 

elevation.

Cartridge Valves

The lowering valve, as discussed above, is of cartridge construction and is virtually maintenance free. 

If a malfunction occurs, refer to the trouble shooting section. 

To clean the cartridge valve:

1.)

Use a thin tool to push the poppet in from the bottom to open the valve.

2.)

Repeat several times while valve is immersed in kerosene or mineral spirits.  Blow the valve 

dry.

3.)

4.)

Inspect O-rings and the polytetrafluoroethylene (PTFE) extrusion washer. 

Reinstall the valve. Tighten the valve in its seat to approximately 30 ft-lb.

Velocity Fuse

There is a brass velocity fuse with a stainless steel spring in the base of each cylinder.  The fuse is a 

safety feature that activates if a pump failure occurs. 

If the pump were to fail,

 the 

deck

 

would

 lower 

much 

more rapidly

.  

However, a

s soon as the descent speed exceeds 

a

 preset 

threshold 

speed, the velocity fuse 

closes and 

prevents

 oil

 from 

flow

ing.

 

When the fuse shuts, t

he platform 

stop

s

 lowering and maintain

s

 

position

 until 

hydrualic 

pressure is re

e

stablish

ed. This safety feature reduces the 

likelihood

 of personal 

injury or 

property 

damage 

as a result of 

pump failure

. To reset the velocity fuse

,

 briefly activate 

the 

pump by 

pressing the 

"RAISE"

 button.

Summary of Contents for AHLT Series

Page 1: ...power unit requires a minimum air supply of 70 CFM at 70 PSI AHLT SERIES AIR HYDRAULIC SCISSOR TABLES OWNER S MANUAL Revised11 13 A company dedicated to solving ergonomic and material handling problems since 1955 AIR HYDRAULIC SCISSOR TABLE MODEL AHLT Website www vestil com Ergonomic Solutions Contents Safety Precautions 1 Operation 1 4 Installation Instructions 2 Pneumatic Hydaulic Circuit Diagra...

Page 2: ...a level even surface a Anchor the table to the floor with appropriately matched anchor bolts b Measure the diameter of the bolt holes in the base of the frame and install bolts that are at least 4in long to anchor the table to the floor c Shim the table to level it Grout under the base of the table to provide additional resistance to warping and bending forces applied to the base between shims Gro...

Page 3: ...ontrols the lowering speed of the table It is preset and cannot be changed Releasing the LOWER control button deenergizes the solenoid and closes the valve poppet This prevents oil from returning to the reservoir and consequently the cylinders stop retracting The deck will maintain its elevation Cartridge Valves The lowering valve as discussed above is of cartridge construction and is virtually ma...

Page 4: ...s current elevation Be certain no person or object is in the way while the unit descends If the unit is overloaded the deck will not rise Instead the relief valve will open due to excessive pressure buildup ans oil will bypass the cylinder and flow into the reservoir Always remember 1 the motor operates only while the RAISE button is pressed and 2 the lowering solenoid valve is energized only whil...

Page 5: ...5 HYDRAULIIC LINE AIR SUPPLY LINE AIR PILOT LINE PNEUMATIC HYDRAULIC CIRCUIT DIAGRAM NOTE Operation of this machine without a filter lubricator will void the warranty ...

Page 6: ...6 AHLT SREIES AIR HYDRAULIC SCISSOR TABLES ...

Page 7: ...ESCRIPTION CYLINDER MOUNT SPRING PIN CYLINDER MOUNT PIVOT PIN CYLINDER MOUNT BEARING HYDRAULIC CYLINDER CYLINDER SEAL KIT NOT PICTURED ROLLER PIN ROLLER ROLLER BEARING ROLLER WASHER ROLLER SNAP RING HINGE PIN HINGE PIN BEARING PIVOT PIN GREASE ZERK PIVOT PIN BEARING PIVOT PIN ROLL PIN PIVOT PIN PIVOT PIN WASHER TOE GUARD HANGER NUT TOE GUARD HANGER WASHER TOE GUARD CORNER PIECE TOE GUARD ALUMINUM ...

Page 8: ...se c Foreign material in flow control valve d Binding cylinders e Foreign material in velocity fuse a Correct as necessary b Add fluid Refer p 10 parts B1 and C for proper fluid level and type c DO NOT CHANGE RELIEF VALVE SETTING Instead reduce the load to rated capacity d Remove and clean e Inspect all fittings for proper fit f Remove and clean g Remove solenoid valve Check and clean Refer to p 3...

Page 9: ...n press the down button d See 1 h e To unlock the fuse repressurize the hydraulic system f Refer to p 3 Velocity Fuse a Leaking hoses and or cracked fittings b Check valve is stuck open The combination of a stuck Check Valve and open Soleniod Valve will cause excessive speeds c Foreign material stuck in Flow Control Valve In this case table lowers initially at a normal rate then speeds up as the p...

Page 10: ...il should be 1 to 1 1 2 below the top of the reservoir tank with the deck fully lowered Add oil if necessary 2 Check for oil leaks see Troubleshooting on p 8 9 Resolve the issue as described 3 Check roller bushings axle pins clevises and pivot points for severe wear 3 Check the hydraulic system for worn or damaged hoses Replace damaged hoses as necessary 4 Inspect each roller for looseness and sev...

Page 11: ...11 LABEL PLACEMENT DIAGRAM ALL LABELS MUST BE UNDAMAGED AND READABLE ORDER REPLACEMENT LABELS WHEN NECESSARY Copyright 2013 Vestil Manufacturing Co ...

Page 12: ...s defects in the following original dynamic components motors hydraulic pumps electronic controllers switches and cylinders It also covers defects in original parts that wear under normal usage conditions wearing parts such as bearings hoses wheels seals brushes and batteries How long is the warranty period The warranty period for original components is 1 year The warranty period begins on the dat...

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