SOME ENGINE" INNOVATIONS.
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A Resume of Recently Published Patents,
4N interesting invention is described
• in patent, specification No. 194,261, by the Soc. Anon. des Ateliers d'Avialion Louis Breguet. It relates to twostroke engines, of the type in which the charge is initially compressed in a separate chamber or cylinder, and admitted to the power cylinder when the piston of the latter is near the upper end of its exhaust stroke, The fuel is injected into the highly compressed air as this enters, and the air is at such a pressure and temperature that spontaneous ignitionA occurs. It would appear that the inventors, as might be expected, are mainly concerned with the production of an engine suitable for use in connection with aircraft, and the princia pal object is that of obviating any difficulties which might arise at different altitudes.
In this engine each power cylinder is supplemented by a two-stage compreseor cylinder of unusual design, and the connecting passage between them is opened or closed by a valve. This also controls the admission of fuel, in such a way that, as it opens the port between the two cylinders, it also opens the fuel inlet passage and at the same time, by mating' itsed on an upper facing, prevents any leakage along its own stem. When this valve closes the inter-connecting port, it simultaneously cuts off the fuel supply. The compression cylinder is the most interesting, for of its two stages the first takes place. in the smaller compartment, that between the portion of the cylinder which is below the piston and the trunk extension of the latter. piston, is an inlet valve admitting air, atenormal pressure, at the ends of the cylinder— both ends are closed, and the trunk of the piston works in a gland in the lower cover. .A valve in the piston itself affects communication between the two ends ; it is spring closed, and opened, to allow compressed air below the piston to pass, by a tappet. screw secured in the lower cover of the cylinder.. Both inlet, valves are mechanically operated.
On the up-stroke, the lower valve is opened, admitting air to the underside of the piston. That air is compressed on the down-stroke, auring which the inlet valve above the piston is opened, so that the cylinder above the piston is filled with air at atmoepherie pressure by the time the valve in the piston is opened to allow the compressed air to pass, and to augment the air already in the -upper portion of the cylinder. On the next up-stroke that air is further compressed into the clearance space above the piston, and is at a pressure of appioximately 50 kg. per sql cm. -when the valve opens and allows it to pass to the power cylinder.
Modification of the pressure in the compressor, by manipulation or adjustment of the inlet valves, provides for variations in the pressure of the atmosphere as experienced at different altitudes. For example, when comparatively near to the ground, one stage of compression might be eliminated entirely by arranging that the inlet valve to the underside of the piston of the compressing cylinder be held open. As the altitude increased beyond a certain limit, 1334 the arrangement might be that the closing of this particular valve should be delayel for various periods, until at, say, 6,000 metres above sea-level, this inlet valve might be allowed to come into full operation. As a refinement, an aneroid barometer might be made use of to control the working of the valve in question, so that the working pressure above the piston in the compressing cylinder should be maintained at a constant value.
The power cylinder of this engine is, in the ordinary way, equipped with mechanically operated exhaust valve located in the cylinder head, or in the position which it would occupy in a fourstroke engine. In the case, however, of an engine being desired for operation at unusual altitudes, in a particularly rarified atmosphere a different construction would be adopted, this exhaust valve being ,eliminated, and two ports, one for inlet and one for exhaust, cut in the wall of the cylinder, -after the manner more usual in two-stroke engines. This would make it possible for compression to take place inaithe power cylinder as well as in the compressor, so providing that the total weight of air admitted should remain the same, whatever the altitude attained by the aeroplane or airship. IMPORTANT advances in connection with the construction of sleeve valves appear to be indicated by two patents which have been taken out by the Soc. Anon. des Anciens Ft. Panhard and Levassor. In one, No. 194,674, the practice of lining these sleeves with white metal, thus reducing the frictional resistance to movement, besides facilitating the manufacturing processes, is protected.
The other, No. 199,712, we regard as the more important. It has evidently been brought into being as the result of experience in the use and working of sleeves described in the first, specification. It is well known, state the patentees, that waste of oil and other inconveniences arise owing to the necessity for allowing ample clearance', between the walls of the sleeves and of the cylinders in or about which they slide. With white-metal-lined sleeves, however, it has been found practicable to reduce this clearance by 50 per cent., from a minimum of six hundredths of a millimetre to three hundredths, thus effectively contributing to economy of oil and to the suppression of the other inconveniences.
Other Patents of Interest.
SOME details of the Moehl six-wheeled chassis, •which was exhibited for the first time, it may be reanembered, at, Olympia last year, are disclosed in specification No. 212,293, by S. Moehl. The main frame runs straight, through from end to end. Both front and rear axle are steered, the Ackerman principle being apparently favoured. The intermediate axle is the driver, and supports the chassis by means of a pair of semi-elliptic springs. These are attached to the frame at their front ends, rest on the axle at their centres, and at the rear ends are pivoted to the forward ends of a pair of long levers, these being supported at their rear extremities by the back axle, and pivoted to the main frame at or near their centres.
A MODIFICATION in fuel supply sys
tems is outlined in speolfiestion No. 212,316, by W. W. Hamill. It has reference to those fuel-feed systems whick embody siphonie means of compelling flow, and makes simple provision for restarting the iphonic action in the event of the conne-Aion being broken. A pipe is provided which connects the engine induction manifold with a suitable point in the fuel-feed system, and a. special form of tap is used for controlling the connection. This device is also designed for use when supplying mixture direct for starting purposes.
THE change-speed gear described in specification No. 212,483, by F. 3. Healey, incorporates in 'its design a number of gearwheels, arranged side by side on the layshaft, and each slightly smaller than its neighbour on the one side, SO that together their contour is like is cone. A single sliding wheel on the main shaft can be brought into mesh with any one of these gears, thus affording a number of changes in a simple box of small dimensions.