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Hydraulic Servo-motor for Heavy Vqhicles

8th September 1944
Page 36
Page 36, 8th September 1944 — Hydraulic Servo-motor for Heavy Vqhicles
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APOWER DRIVEN pump and accumu

lator for amplifying the hydraulic braking system of a heavy vehicle forms the subject of patent No. • 562,589, from J Pratt and G. Girling, both of Guildhall Buildings, Navigation Street, Birmingham, 2. The pump is driven by the propeller shaft of the vehicle, ensuring that, if the wheels he turning, the pump must be driven.

Referring to the drawing, the propeller shaft is formed into an eccentric (1), which reciprocates a piston (2). This piston is shown with its upper half in the retracted position and its lower half fully extended. In a co-axial cylinder is an accumulator piston (3),, loaded by powerful springs housed in a casing (4); this casing also acts as a reservoir for the fluid. The strength of

• 'the loading springs is such thatthe maximum pressure stored is 1,000 lb. per square in., the minimum being 800.

In action, fluid is drawn into the pump chamber, via duplicated inlet valves (5), and, after compression, is ejected through the exit valve (6), through a passage (7), and, finally, reaches the storage space (8), where it displaces piston (9) When the reservoir is filled, the piston-rod (10) compresses a trapped rubber sleeve (11) and withdraws the pump piston from the orbit of the eccentric.

The brake pipes are connected to the pressure space, via the usual control valve (not shown), which is constructed so as to give the driver a sense of " feel " over the amplified force.

COOLING SYSTEM FOR ROTARY VALVES

INpatent No. 562,549, from F. Aspin, 149, Walmersley Road, Bury, Lanes, is described a scheme for inducing a flow of cooling air through the interiot of a rotary valve. This inventor proposes to use p. dual system for creating air circulation—an impeller assisted by an exhaust-operated ejector.

The drawing snows an air-cooled engine incorporating the suggestions. The rotary valve of the well-known Aspin form, is hollow and is open to the atmosphere, via a central tube (1) connected with a duct (2). After the air has received heat from the valve, it is extracted by a rotary impeller (3). aided by an exhaust-driven ejector (4).

The object of using the two methods is that the impeller action is proportional only to engine speed, whilst the ejector action varies with the gas flow, and the resulting combination is said to ensure that the degree of cooling varies exactly with the load on the engine.

THE I.A.E. GAS-AIR MIXING VALVE

Tniaifftain a constant gas1 air ratio over the whole working range of an engine is the object of a mixing valve shown in patent No. 562,526, by W Michalski and the'Institution of Automobile Engineers, 12, Hobart Place, London, S.W.1. The device is intended for coimpression-ignition engines.

Two designs are shown, one employingcastings, the other, which we illustrate, being built up from standard pipe fittings. A T-piece has one end (1) leading to the engine intake, the other end (2) being the gas inlet. The branch-pipe (3) forms the

path for the incoming air. A throttle (4) is connected to the accelerator pedal, and controls the supply of gas only. The amount of air admitted is governed by a valve (5) which can open or close the air inlet. Complete closure is prevented by holes drilled in the valve head, also by an external stop-screw (6) The valve (5) is opened by the passing gas flow against the tension of an adjustable exterior spring.

As this valve is operated by pressure difference, its return

spring can be chosen so that it maintains a -constant mixture sOngth throughout the whole speed range. At partial loads the gas only is throttled, this being a desirable feature when oil is used for ignition purposes. At idling' speeds, the air valve closes, passing only sufficient air to maintain the fire in a workable condition.

THERMO,SIPHON-PUMP COOLING SYSTEM THE thermo-siphon principle of water circulation has the advantage that its action depends on temperature difference, and it is, therefore, most effective when the need is greatest. In a pump-driven system, however, the

degree of cooling varies with engine speed, and this may not always be desirable: To incorporate the advantages of the Thermo-siphon principle in a pump system is the object of a modification shown in patent No. 562,484, by the Austin Motor Co., Ltd„ and H. Charles, both of Longbridge Works, Birmingham.

The drawing shows a pump-actuated cooling system with the proposed modi-. fication; this consists of a by-pass pipe (1) across the top and bottom of the radiator. In action, when the engine is cold, the greater part of the water flow will be short-circuited by the bypass, and only after the temperature has risen considerably will the therninsiphon action bring the radiator . into play.

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Locations: Birmingham, Bury, London

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