Bottle Jack by SVT and TirionFordring


By: Andrew Basin

The inner workings of a bottle jack are fascinating. The jack is a hydraulic (liquid based) press, meaning it pumps liquid (oil) into a pressurized oil canister, pushing the piston up. Two check valves, valves that  only permit one directional flow of the oil, monitor the pressure of each cannister.



The way a check valve operates is relatively simple. Let us have two sides, A and B. It allows flow from side A to B, but not B to A. The valve has a spring which by default keeps the valve closed. The plug is too large to fit through the small pipe on side A, while it can retract into side B if pressure is applied from side A. This means that the valve will open if, and only if, there is high pressure on side A and low pressure on side B. The pump pressurizes the oil that is trapped between the two valves.

When the pump is at low pressure, the reserve oil is at a higher pressure than the pump. That means it can go into the pump canister. The pump increases the pressure in the pump canister, meaning it is higher pressure than the pressurized oil canister, and allows the check valve to open. After the pressurized and pump canisters’ pressures reach an equilibrium, the valve is closed by the spring. As liquid can not be compressed, the high pressure oil pushes the piston up, lifting the object of interest.

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Here is a video animation of how it works.