A High-efficiency Two-stroke I -1 A TWO-STROKE engine appearing in patentNo.
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684,366, is claimed to have 'a power output of 1.9 times
that of an equivalently sized four-stroke. This high value is obtained by the use of a novel method of scavenging and charging. The patentee is P. Martinelli, Via Montesanto 7, Rome. ' The drawing shows one cylinder of a multieylindered engine. The mixture is compressed by a blower (1) and fed to a manifold, where it awaits admission by the inlet valve (2). Exhaust ports (3) are located in the cylinder walls, and are uncovered by the descending piston. The crankcase of each cylinder is closed off and forms a compressing space for air.
in operation, as soon as the exhaust port is uncovered, a valve (4) is opened; this controls a transfer port (5) from the crankcase and lets in the compressed air to act as a scavenging charge. When the bottom of the stroke is reached, the main charge of
684.366
mixture enters via the inlet valve, and for a few degrees the exhaust, the scavenge-air valve and the main inlet are all open at once.
The main inlet valve is the last to close, and the actual compression stroke extends only over about 60 degrees.
ELECTRIC PETROL INJECTION
INJECTION equipment for use with I a petrol engine forms the subject of patent No. 682,781, which comes from Thompson Products Inc., Cleveland, Ohio, U.S.A. The injectors are electrically operated', in sequence by a tithing device resembling that of the ignition system.
The drawing shows one of the injectors'. in place in the cylinder-head, with, the sparking plug beside it. fuel-arrives under a constant pressure
T and is led to the conical seating housing the admission valve (2).
A38 The stem of the valve extends upwards to carry an armature (3) lying between electro-magnets (4 and 5). A light spring biases the valve into the closed position.
In operation, t he lower magnet, when energized, pulls the armature down and so opens the valve. After a timed interval, the upper magnet is energized, and the valve closes. Both the opening and the closing are electrically controlled, the closing spring serving only to maintain closure after the electric system has been switched off. .
The timing device can vary the period of opening to suit the power output required from the engine.
A NOVEL CYLINDER-HEAD BY DAIMLER-BENZ
A N unorthodox layout for a cylinder 1-1.and head is shown in patent No. 684,873, by Daimler-Benz A.G., Stuttgart-Untertiirkhelm, Germany. The aim is to improve combustion efficiency and at the same time to simplify production.
The drawing clearly illustrates the novel arrangement in which the cylinder-head, with its valves, is set at an angle on the cylinder block. The combustion space, which would be rather an odd shape, is converted as nearly as possible to a hemispherical form by cutting away the piston as at I, and forming a cavity in the inlet valve (2).
The exhaust valve (3) -is covered by the piston at topdead-centre, a n d receives therefrom some measure of heat protection. The combustion space is said to be a favourable one from the point of view of preventing detonation.
AN" OVER-SQUARE" ENGINE
pATENT No. 683,113 comes from Daimler-Benz A.G.. StuttgartUntertiirkheim, Germany, and shows an " over-square ' engine, that is, one in which the diameter of the cylinder is greater -than the•r.troke. The design takes advantage of the large bore to enable the valves to be inserted through the cylinder, this cheapens production by enabling the cylinder-head, cylinder
and crankcase to be made as a single casting, a form of construction which also makes for greater rigidity. , The drawing illustrates the scheme clearly; the one-piece casting containing both inlet and exhaust ports. High output and high speeds are claimed for the engine, largely on account of the low piston speed and improved cooling obtainable.
The one piece casting enables good water passages to be used, arid they can even be extended down to the region of the main bearings.
A UNIVERSAL JOINT
FROM R. Burtwell, " Essendon," Sandhurst Road, Crowthorne, Berks, comes patent No. 683,833, in which is disclosed a new type of universal joint. A novel point is the use of steel balls as keys to form a torque-transmitting member. Referring to the drawing, the driving member terminates in a cup member (I) which is centred by a ball-ended stud (2); this is free to slide in order to accommodate changes in length. The driving torque is transmitted by balls (3) sunk into hemispherical recesses in the central member, and sliding in grooves (4) formed in an outer sleeve.
The grooved sleeve is surrounded by a rubber bushing (5), which provides a measure of resilience in the drive.
NO-CHARGE WARNING DEVICE 'ROM C.A,V., Ltd., Warple Way, I London, W.3. comes patent No. 684,855, describing an improved dynamo-battery circuit. The aim is to warn the driver should the dynamo cease charging during running. _The patent gives the full circuit, which includes a light which automatically comes on if charging ceases.