During the COVID 19 event I decided to spend some time looking at my old OMIC pump up pallet truck. I got this to move the BEDFORD ELECTRIC CF2 BATTERY PACK over 1000kg weight. After one attempt I decided to develop the rail track idea because of the friction! Loaded I couldn't pull the battery out. Anyway I put it away for some years then one day I acquired an industrial robot I tried to use the pallet truck but found it would raise but not lower!
The only way I could drop it was to unscrew the pressure relief valve.
In the last week I decided to strip it down to find out how it is intended to work.
In normal use there is a foot operated valve at the base AC = RAISE CW = LOWER
Turning the lever clockwise (CW) should lower the truck but nothing happens...
Removing protective cover at the front of the bottle jack revealed two spigots. You can see on the right. The closest one sets the rate of decent, and is operated by the screw travel in the UP/DOWN leaver.
So when the lever is turned clockwise the pin moves forward and presses on a ball bearing opening the valve.
At the same time a CAM on the leaver handle pushes in a BUTTON this opens the second non return valve. So basically its a matter of adjusting the position of the two screw in ball valves to correspond with the cam on the leaver - SYNCHRONISING THEM
On the left is the LOWER RELEASE BUTTON spring loaded. Center is the screw in pin , clockwise = lower, right is the leaver STOP
TO FIX IT STEP ONE DRAIN THE OLD OIL
STEP TWO REMOVE BOTH BALL VALVES
STEP 3 CLEAN EVERYTHING IN WHITE SPIRIT
STEP FOUR Screw in the two valves by hand about half way.
SCREW IN THE LEAD SCREW FULLY CW
STEP FIVE put in new oil I used 1/2 litre
STEP SIX start pumping the handle, at first nothing will happen.
STEP SEVEN slowly screw in the longer valve until the forks begin to lift.
STEP EIGHT screw in the shorter ball valve (in line with the lead screw) until the forks stop moving.
STEP NINE - THIS IS THE HARD BIT refit the leaver cam IN THE DOWN POSITION (FULL CW) and PRESS AND HOLD it firmly towards the pump body. There should be no gap.
THE FORKS SHOULD DROP NOW
In this position the button should be fully pressed in ..
STEP TEN HOLDING THE CAM IN ! Tighten the Allen screw in the leaver.
NOW TRY LEAVER ANTICLOCKWISE Raise position check
STEP ELEVEN Refit the outer leaver cover spring and retaining screw.
You may want to fine tune the position of the two ball valves to get the leaver position to match the two positions exactly.
STEP TWELVE on the side there is a screw with a lock nut - this sets the safe operating jack force. To calibrate you would need a load cell or a 2 ton weight!
Don't unscrew it too far or the spring ball and cup + all the oil will come out!
On the other side there are two plugs . Behind the brass plug is a brass gauze oil filter.
The larger plug is the oil drain plug.
Completed truck
No comments:
Post a Comment