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A Pump That Cannot Contaminate.

22nd December 1925
Page 11
Page 11, 22nd December 1925 — A Pump That Cannot Contaminate.
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Which of the following most accurately describes the problem?

AMON users of commercial motors the must occasionally arise the need for a pump which will raise air, or gas in circumstances where the air or gas must not come into contact with the oil used in-lubricating a piston working In a cylinder. Take, for instance, the raising of milk or other fluids equally subject to becoming tainted if brought into the presence of oil or even air that has been compressed in a lubricated cylinder, In such a case the possibility of obtaining a supply of clean air would often overcome a difficulty and facilitate transport. We have recently examined a very clever pump, which would appear to fill such a need. It is made by the Nash Engineering Co., of South Norwalk, Conn., U.S.A., and is of special interest because of the very original means employed for producing pressure or a 'Vacuum.

Our illustration shows a rotor revolving in an anti-clockwise direction, and it will be seen that the casing, instead of being round, as usually constructed, is of oval form. The blades of the rotor nearly touch the casing at the points where its sides are flattened, and are far away at the points of the major axis.

A certain quantity of water is necessary to enable the pump to'work, hut this water is no part of the discharge which the pump delivers, being merely driven round and round by the blades of the rotor so as to form a seal. Centrifugal force is set up when the revolving stream of water attains a certain speed ; this force keeps the water in close contact with the Outer wall of the casing, and, as it follows this oval r.ath, it will be seen that at two points the water comes near the body of the rotor, entirely filling the gaps between the blades. It is obvious that when any one of these spaces is tilled with water any air that was there must be driven out through the outlet ports, and that, when the water is at the point farthest from the centre of the rotor, a vacuum must have been created. Pour ports are provided in the side walls of the body, and are shown as inlet ports and Outlet ports. As each space between two blades reaches an inlet port the water, in drawing out of the space, creates a vacuum, which is at once filled by air.

As the space approaches the outlet port, the encroachment of the water drives the air out of the space, which is then immediately ready to be charged from the next inlet port. This action takes place in each space in turn.

The action of the pump may be described as that of a multi-radial piston pump, but with water for its pistons, and the air or gas being primped enters and leaves spaces Into which lubricating oil does not obtrude.

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Locations: South Norwalk

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