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A Swash-pl ate

23rd June 1944, Page 36
23rd June 1944
Page 36
Page 36, 23rd June 1944 — A Swash-pl ate
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Variable Gear

(IF all the schemes proposed for L./infinitely variable gears, the swashplate pump-and-motor type is/probably the soundest in principle, although, hitherto, its low mechanical efficiency has ruled it out for .road-vehicle transmission systems. This will, doubtless, be improved in tame, and patent No. 560,662 shows the latest proposal in this respect. The inventor is G. Wahlmark, Rockford, Illinois, U.S.A. Only the briefest outline can be given here, as the specification runs to 18 pages of letterpress and 21 drawings.

The gear consists of a pump portion (1) end a motor member (2). The pump swash-plate (3) is adjustable and can be set to give any ratio between unity and 1.000 to 1 or more. It is proposed to provide automatic ratio selection in accordance with the load and, to this end, the throw of the primary swash-plate is adjnsted by a Piston (4) which is subject to both the hydraulic pressure and a speedresponsive device; The motor swash-plate (5) is of fixed throw and, when a low ratio is being transmitted, exerts a backward reaction on its casing which is resisted by a brake band (6). As the ratio approaches 1 to 1, the reaction diminishes until it is exactly cancelled Out by the input torque ; when this occurs, band 5 can be released. and a straight-through drive is', then established. The efficiency in top gear, therefore, should be of a reasonably high value.

A reverse is obtained by rocking the primary wobble-plate (3) past its neutral position to an opposite angle, and to this end the piston (4) functions in a, double-acting manner, suitable valves controlling the admission of fluid to one side or the ether. one day, be available to the road user, and a possible example of this is shown in patent No. 560,549, by Ford Motor Co., Ltd.', 88, Regent Street, London, W.I. 'This patent shows a V-type engine fitted with pairs of overhead camshafts, one for the inlet and one for the exhaust valves.

In the drawing, the exhaust camshaft is shown at 1 and the inlet shaft at 2; each is fitted with a worm wheel meshing with a common worm mounted on a shaft (3). The latter, at its lower end, carries a worm (4) driven by a worm wheel (5) on the crankshaft. The helix angle of the teeth is in the neighbourhood of 45 degrees, to ensure maximum efficiency: The main advantage of the design is that the ends of the camshafts extend from their housings and are readily available for driving the numerous auxiliaries required on a modern engine. In addition,. the parts are said to be lighter and more compact 'than are those employed in conventional methods.

A SLEEVE-AND-PISTONVALVE TWO-STROKE rLAIMErr to give highly

efficient scavenging, a design of two-stroke engine is shown in patent No, 560,409, by J. Jameson, Chessington Lodge, Spring Street, Ewell, Surrey. In this engine, a piston valve controls the inlet and a sleeve' valve is used for the exhaust. The inlet valve (1) 'works in an upper 'cylinder and is provided with ports which open the inlet manifold (2) to the combustion area; the inlet manifold is kept supplied with air for mixture under pressure. The exhaust ports (3) are disposed near the upper end of the cylinder and are controlled by a ported sleeve valve (4), which is shown in the open position. The improved scavenging is due, partly, to the fact that the piston, on its upstroke, helps to expel the gases,, and, additionally, to the effect of the incoming charge. This, at top dead centre, issues from the venturi (5) and, striking the piston well (6), curls outwards and upwards towards the ring of exhaust ports, thus removing the last vestige of the burnt charge.

TO diminish the space required on the chassis is the main object of an improved design of pump for operating hydraulic tippers, shown in patent No. 560,647, by Edwards Bros. (Tippers), Ltd., and others, all of Springfield Garage, Bradford Street, Bolton. The design shown operates on the awashplate principle, and the chief improvement is the abolition of one of the shaft bearings, reducing overall length.

The drawing shows sufficient of the pump to illustrate the modifications : 1 is the thrust bearing that operates the plungers ; this is mounted on a wobbleplate carried on two bearings (2 and 3) The former is of the combined journaland-thrust type and it 'is upon this feature that the patent rests.

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Locations: Rockford, Surrey, London

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