A Different Kind of Engine

By Staff
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Fig. 1

26 Kicked Lane, Uncasville, Connecticut, 06382

How about an internal combustion engine that has no flywheel, no
cooling jacket, no moving parts except a few mushroom valves,
practically no lubrication, is light weight and has a high thermal

This sounds like a tall order, but Herbert A. Humphrey of
England invented a machine that had these qualities. His invention
is commonly called the Humphrey Gas Pump and it was used to pump
water and compress air. Its outward appearance has no resemblance
to an internal combustion engine; it is only in operation that the
two are similar.

For heads up to 50 feet, the gas pump is very simple. A piece of
pipe with a stand-pipe at one end and a combustion chamber at the
other, the latter being surrounded by a few simple fittings. Figure
1 is a diagram of the simple pump. It consists of a conical
explosion chamber C, fitted at the top with inlet valve I, the
exhaust valve E, and a scavenging-valve not shown. A simple
interlocking gear is arranged between these valves by means of
which, when valve I has opened and closed, it is locked in the
closed position and valve E is released. When valve E has opened
and closed, it is locked and valve I is released.

Imagine a charge of gas and air compressed in the top of chamber
C and fired by a spark plug which projects through the top of the
casing. All the valves are shut when the explosion occurs, and the
increase in pressure drives the water downward in the pump and sets
the whole column of water in the discharge pipe in motion. The
column of water attains kinetic energy while work is being done on
it by the expanding gases, so that when these gases reach
atmospheric pressure the column of water may be moving at say, six
feet per second. The motion of this column of water continues until
the pressure behind it falls far enough below the atmosphere to
open the exhaust-valve E and the water valves V. Water rushes in
through these water-valves and follows the moving column in pipe D,
and at the same time it rises in chamber C in an effort to reach
the level in the suction tank.

When the kinetic energy of the moving column has been expended
in forcing water into the high level tank, it comes to rest and,
there being nothing to prevent a return flow, the column starts to
move backward toward the combustion chamber and continues with
increasing velocity until the water reaches the level of the
exhaust valve, which it shuts by impact. A certain part of the
burned gas is trapped in the cushion space beneath the inlet valve,
and the energy of the moving body of water is expended in
compressing this burned, gas to a greater pressure than that due to
the static head of water in the tank T. A second outward movement
of the column now begins and when the water reaches the level of
valve E, the pressure in the compression space is again atmospheric
and further movement of the water opens valve I, which has been
released by the interlocking device, thus drawing in a fresh charge
of gas and air. Once more the column of water returns under the
pressure of the elevated tank and compresses the charge of gas and
air, which is then ignited to start a new cycle of operations.

Ignition is timed by an apparatus resembling a pressure switch,
which closes the electric ignition circuit at the point of maximum
compression, and an ordinary battery, coil and spark plug.

In starting the pump for the first time, compressed air is
allowed to flow into the combustion chamber until the volume of the
air thus introduced is slightly larger than the usual charge. The
exhaust valve is then suddenly opened by means of a hand lever, and
the escape of the compressed air permits a movement of the water
column, which gives the cushion and suction strokes, and so draws
in a fresh combustible charge, which, on ignition, starts the
engine (pump) working regularly. If the pump is stopped when
working regularly, it will always stop with a fresh charge in the
combustion chamber, under pressure, so that the only operation
necessary for starting is to close the switch on the ignition
circuit. The pump can therefore be started and stopped from a

The Humphrey Pump described above works on the four-cycle
principle, requiring four strokes for completion of one cycle. The
time required for the completion of a cycle is governed in design
by the length of the ‘play pipe’ D. Typical rate might be
on the order of 12.5 cycles per minute. Other variations of design
used double cylinders to draw water twice each cycle and in effect
operate as a two cycle pump. If the column of water oscillating in
the play pipe of a Humphrey Pump is used as a water piston and
caused to rise and fall in an air vessel fitted with suitable
valves for the inlet and outlet of air, the combination constitutes
an air compressor of high efficiency.

I do not have information on the number of Humphrey Pumps built
or years they were built, but it appears that units which could
pump against a head of 300 feet were built, and units in excess of
35 horsepower were built by 1923.

Information for this article has come from the 1923 McGraw
Hill Book Company, Inc.’s book, Internal Combustion

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