chingford pumps

del rio


operating cycle






The pump is essentially a 'U' tube of water, with one end closed off where a gas mixture is introduced and exploded. The operation follows the usual 4-stroke cycle, of induction, compression, expansion and exhaust, with all the valves being atmospherically operated.

The Main Components

Referring to the diagram below, the pump consists of an explosion vessel C, fitted at the top with an exhaust valve E, an inlet valve A, and a scavenger valve next to A but not shown in the figure. Below the explosion chamber is a length of piping provided with the water inlet valves, W, through which the water to be pumped enters from the Supply Tank, S.T. Beyond this is a “play” pipe, terminating in the reservoir, E.T.

Humphrey Pump Diagram

Power Stroke

As the gases expand, the water column is forced along the play pipe to the reservoir ET. The water column is still moving when the pressure in the explosion chamber drops below atmospheric pressure, thus the exhaust valve, E, air scavenge valve and water valves, W, all open. Water flows into the play pipe to fill the space left by the water column and fresh air enters through the scavenge valve to fill the space F.

Exhaust Stroke

When the column of water begins to flow back again, the exhaust gasses are driven out of the explosion chamber through the exhaust valve which has remained open. The valve is closed by the action of the water and the air trapped in space F is compressed as the column of water is bought to rest.

Induction Stroke

The water column is pushed back by the ‘air spring’ in space F and when the pressure falls below the atmospheric pressure the inlet valve, A, opens sucking in a fresh charge of gas mixture. An interlocking gear is provided, so that the scavenger and exhaust valves, after being closed, cannot open again until the inlet valve has both opened and closed.

Compression Stroke

The next return stroke of the water column compresses the gas mixture with is ignited when the pressure reaches a maximum, and the cycle starts again.