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The Control of Exhaust Braes

1st June 1956, Page 141
1st June 1956
Page 141
Page 141, 1st June 1956 — The Control of Exhaust Braes
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THROTTLING the exhaust is coming I. more into use for braking vehicles, but it is important thlt the throttling should not be carried far enough to cause the engine to stall. A control mechanism for rendering this impossible is shown in patent No. 744,513 (Clayton Dewandre Co., Ltd., Titanic Works, Lincoln).

The exhaust pipe (1), upstream of the silencer, is fitted with a butterfly valve for throttling purposes. It is worked by rocking an external arm (2). A solenoid (3), when energized, can pull the arm into the throttling position against the force of a spring (4).

This spring is made to have an increasing rate; one way of doing it is to use two springs of differing lengths as shown. This is done because the resistance to movement is greatest when the throttle is shut. This can be offset, however, by using an off-centre butterfly valve.

Energization of the solenoid by closing a switch (5) applies the brake; the switch can be worked by the usual brake-pedal before the wheel-brakes come into action. Stalling of the engine can be prevented by the use of a centrifugal switch, or by taking the operating current from the dynamo side of the cut-out. A pressure-sensitive switch is also mentioned.

EXTRICATING A BOGGED VEHICLE

PATENT No. 746,636, shows a simple device for enabling a vehicle to raise itself when bogged. The patent comes from R. Omant, R. Grant and A. Martin, 1 lc Castlereagh Street, Sydney, Australia.

A tubular "spoke" (1) is provided with brackets (2) fitted with screws for jamming it outwardly into the wheel rim. Inside the tube is an adjustable screwed rod fitted with a swivel foot (3) on its end. The unit is attached to a bogged wheel as shown at 4, and when power is applied it should lift the wheel far enough to enable packing to be placed under it.

A NEW FUEL-INJECTION SYSTEM

THE conventional injection pump is very lightly loaded until the actual moment of injection; then, the load is, for a short time, very heavy. This means that the construction of the pump and its camshaft has to be designed for this maximum but transient load. To avoid this, it has been proposed to pre-compress the fuel and to use a timed injector as an on-off valve. The objection to this method

is that it an injector should stick in the open position it would discharge much of the fuel supply into one cylinder. Patent No. 746,280, shows an injection system that makes the best of both principles. The patent comes from the British Internal Combustion Engine Research Association, 111-112 Buckingham Avenue, Slough.

In the proposed scheme, fuel is pre-compressed to about half-injection pressure. It is then used as a hydraulic fluid to work the normal helically edged pump plunger. The pump camshaft has little work to do, having only to operate the slide-valve controlling the hydraulic fluid.

A small continuously running pump supplies the pre-compressed fuel to an inlet leading to a pressure accumulator (1), having compressed air on its underside to act as a spring. The pump plunger (2) is lifted by a large piston (3) when the fuel is admitted under it. The events are governed by a slide-valve

assembly shown end-on at 4; this is worked by a light cam and is springreturned.

The arrangement gives very rapid injection irrespective of engine speed; so rapid that an annular dash-pot (5) is provided to decelerate the plunger at the top of its stroke.

Two of the claims made for the system are improved starting and better performance at low speeds.

RUBBER SPRING FOR ENGINE STARTING

PATENT No. 748,078, shows a clockwork mechanism for providing a short burst of power such as would be needed for engine starting. The novel feature of the scheme is that the spring is made of rubber discs which store energy by torsion. The patentee is A. Moulton, The Hall, Bradford-onAvon, Wiltshire.

CONTROLLING PETROL INJECTION A CONTROL system for a petrol injection pump in which allowances are made for variations in volumetric efficiency of the engine, is shown in patent No. 744,806. (The S.U. Carburetter Co., Ltd., Wood Lane, Birmingham, 24.) In the drawing I is the induction pipe and 2 the injection pump. A throttle controlled venturi has a pipe leading from its constriction to a capsule stack (3) which, when expanding, reduces the fuel charge and vice versa. A continuation pipe (4) ensures that air is constantly flowing through this system so that there is little temperature difference.

The throttle is coupled to a cam (5) which controls a variable restriction (6) in the branch pipe; this cam takes control when the throttle moves towards its closed position and isolates the main venturi.

Another pipe (7) carries air from atmosphere to the induction pipe and a small venturi (8) translates it into pressure variation which is then applied to the control pipe via a manually adjusted restrictor (9). This branch, assumes control when the throttle is closed, a position in which the main venturi tends to diminish its effect due to low air velocity.