GB2233400A - Automatic variable pitch propellor - Google Patents

Abstract

In a propeller, for use on boats, ships or aeroplanes, the centre of thrust of each propeller blade is behind its axis of rotation in a hub. A cam or pin protruding from a collar at the base of the blade acts against a sliding ring which compresses a spring or other resilient member inside the hub whereby forces due to fluid flowing over the blades can cause a pitch change against the bias of the resilient member. The thickness of the sliding ring and the position of locking rings may be varied to change the range of pitch available. <IMAGE>

Description

THE AUTOMATIC PROPELLOR This is a propellor designed to change pitch automatically.

This can give vessels much more power when needed at slow speed for acceleration, especially when getting over the hump" to get onto the plane. When planing, a higher pitch gives much more speed than a low pitch. It is also useful for towing or to give maximum speed when a vessel is enipty or fully loaded, these conditions requiring different pitches.

It works on the principle of each of 3 blades having a collar with a protruding roller pin. These pins act against a sliding ring washer which in turn acts against a coil spring. Locking rings are screwed up along the hub to compress the roller pins against the spring. This is the high pitch position. The centre of push of the blade is behind the centreline of rotation.

When the blade has a heavy load against it, as when a vessel is stationary or moving slowly, and the propellor is turned fast (by the engine) the extra load will compress the spring further and allow the blade to turn itself into a lower pitch, and allow the engine to revolve faster and develop more power. When the vessel is planing or moving fast, there will be less load on the blades and the compressed spring will turn them back into a higher pitch.

Claims (6)

THE AUTOMATIC PROFELLOR : CLAIMS

1. An automatically variable pitched propellor comprising a hub containing a spring (metal, rubber or other compressable material) which can be compressed by extra water pressure acting on rotatable offset propel 1 or blades (usually but not necessarily, three in number) mounted on the hub. The blades have protruding cams which operate against the spring and vice versa.The hub can be mounted onto a normal tailshaft in the usual way. The centre of thrust cn each blade is behind its centreline of rotation in the hub, so that with heavier loads on the blade as in towiny, acceleration, heavy weather etc,the blade will be rotated against the spring into a lower pitch and so allow more thrust to be developed and more revolutions and power from th engine. Ey changing the thickness of the sliding ring and adjustment nf the position of the locking rings, any range of pitch may he attained.

2. A propello@ as described in claim 1 where each blade has a collar at its base to allow it to be attached to, and rotate in, a hub.

3. A propellor as described in previous claims where each blade is made with its centre of push behind the centreline of its rotation in the hub.

4. A propello@ as described in previous claims where each blade has a cam protruding into the hub to act against a spring so that it may compress the spring when the load on the blade is heavier than normal.

5. A propellor as described in previous claims where the boss can be + i tted onto a normal propel 1 or shaft, and has a recess into which a spring @@ compressable. material may be fitted. The spring, sliding ring and locking rings are covered by a retaining collar which is bolted to the front half of the hub.

n nut retains the hub @nto the keyed shaft.

6. A propellor as described in previous claims where the boss and blades are made of suitable proportions and materials to be used for aircraft propulsion.