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Aviation History
1937
1937 - 2187.PDF
AUGUST 5, 1937. FLIGHT. Emergency Lowering of Undercarriages THIS patent suggests means of emergency lowering of an undercarriage in the event of a failure of the normal gear. Two arrangements are described, the one using a spring as a source of energy and the other using compressed air. In the first, a spring is normally held in a compressed state by a locking device, such as a tapered conical member bearing against locking balls. This device is released by the pull of a cable, and it then straightens a folding radius rod and lowers the undercarriage. In the second arrangement a hydraulic jack is used in which the ram slides over a fixed rail. The interior of this rail forms a reservoir for compressed air and a manually- operated valve can be operated to cut oft one end of the jack from the hydraulic cir cuit and connect it to the compressed air, which will then force the piston outwardly to lower the undercarriage.—Patent No. 460316: G. H. Dowty. Control of Variable-pitch Airscrews THE advantages to be derived from the use of airscrews in which the pitch is automatically varied in order to keep the speed more or less constant, independent of the power absorbed, are now well known. Means by which this automatic control can be effected are described in this patent. The pitch of the airscrew is controlled by a liquid pressure system acting against the centrifugal force in the blades. A constant- speed electric motor and the air;ra/t engine are both coupled to a valve in the hydraulic system. This valve, when the motor and the engine revolutions are the same, pre vents any flow of oil and so keeps the air screw at the same pitch. When, however, the speeds ot these two units vary, then more liquid is pumped into the pitch-control cylinder or allowed to escape, depending on the relative variation in speed, and in this way the pitch is corre spondingly altered.—Patent No. 457808: United Aircraft Corporation. Shock-absorber Strut T WO patents dealing with the same type of oleopneumatic shock-absorber strut have recently been granted to the Ribbesford Company The general con struction is shown diagrammatically in the illustration. It consists essentially ot two tubes, a plunger A which telescopes into an outer tube B. Attached to the inner end of the plunger is a head C .with suitable sealing glands which con- p tact with the inner surface of the outer tube and which form the subject of the second patent. In this head is an annu- Q lar plate D forming a flutter valve which on the compression stroke exposes a tiumber of holes in the head of the plunger and which closes them on the expansion stroke, thus varying the degree of damping. The air and oil are separated by a float ing piston E which, it is claimed, confers many advantages on the strut. If, for example, an oil leak should develop during flight, the air pressure would "rce the floating piston against the plunger head and so relieve the remaining oil pres sure, thus allowing sufficient oil to be left to ensure a safe landing. further, the packing glands are always working in oil, thus avoiding sliding air Ribbesford shock- absorber strut. The TREND of INVENTION Recent Aeronautical I Patents Reviewed seals. Moreover, the strut will function in any position, since the air is always confined to one end by the floating piston. The con struction enables ordinary drawn tubing to be used, and the strength and resisting move ments are such that the weight is kept low. The second patent relates to the packings in the plunger head These consist of in clined rings, and the space between them is connected to the central opening in the plunger head, and so is always on the side of the flutter valve on which the pressure is greater. In this way the higher pressure is always transmitted to the space between the packings to force them against the cylin der tube and provide an effective seal. Furthermore, the seal has a low static fric tion coupled with a high dynamic friction, particularly during the rebound movement when it is most required.—Patents Nos. 461144 and 461577: Ribbesford Co.. Ltd., and Others. Combating ice Formation A METHOD by which anti-icing liquid can be distributed in a positive manner over a given surface and in which the distribution can be equal or unequal as desired, is described in this specification, and is illustrated in the accompanying diagram. A Dunlop Ant i cer patent which shows a sectional view ot a leading edge in which the device is incorporated. The liquid is contained in a tube B which may be of metal or rubber, as desired. Along the edge of this tube are a number of aper tures, C, through which the liquid can pass when subjected to a comparatively low pres sure of the order of 5 lb./sq in. Inside this tube is a small tube, A, which is capable of being distended by air or hydraulic pressure, whereupon liquid is expelled through the apertures C on to the surface D that it is desired to keep free of ice. Owing to the varying thickness of the tube A along its length, distention will establish annular contact between it and the outer tube at intervals, and thus a volume of liquid will be isolated and ulti mately expelled as described. The intervals of contact between the tubes may be equal or unequal as desired, and thus the volumes of liquid dispelled can be varied from place to place as required.—Patent No. 462570: Dunlop Rubber Co., Ltd.. and J. Wright. \ i: LJ «*•» - H h j T^ ^ Sa JZX .. .2) v& Jack-locking (Pat. No. 458005) Locking Devices M EANS whereby an adjustable strut or a fluid-operated jack can be mechani cally locked in either extreme posi tion is described in Patent No. 458005. The unlocking can be effected either auto matically or by separ ate manual operation. The cylinder and pis ton of the jack or strut are shown in the illus tration! The piston head A has at each end annular projections which are slotted to receive rings of balls B and C, the diameter of the balls being greater than the thickness of the annular projec tions. Grooves D are formed in the cyhnder at each end and the balls are pushed into these by the projections E, at tached to a spring- loaded plunger. When the piston moves to one end of the strut, the balls push back the plunger until they are opposite the groove, when the inclined edge of the plunger forces them into the groove and the plunger slides down inside the ring to hold them in position. The unlocking is effected by the fluid pressure which oper ates the jack and which causes the plunger to move out against its spring. Alternatively, the plunger may be moved by a lever mechan ism F from outside the tube.—Patent No. 458005: Elektronmetall G.m.b.H. Undercarriage Warning Device W HEN an aircraft is fitted with a retract able undercarriage it is very desirable that some indicating and warning device be provided to inform the pilot be fore he attempts to land whether the under carriage is extended or not. With the arrangement described in tins patent no indication is given so long as the aircraft is in the air and flying at normal speed with the undercarriage retracted As soon as the pilot eases back the throttle prior to landing a sign displaying the word " UNDERCARRIAGE " is illuminated and a horn is sounded to warn the pilot to lower the undercarriage. As soon as he commences to do so a red lamp lights up and remains alight until the undercarriage is locked in the landing position, when the sign and the red lamp are switched off, the horn is stopped and a green lamp is lit. In addition to a master switch the system is controlled by switches incorporated in the undercarriage mechanism and by a double switch controlled by the throttle lever.— —Patent No. 457562: Fairev Aviation Co., Ltd.. M. J O. Lobelle and F. Voss. Retractable Undercarriage T HIS retractable undercarriage is com posed of three struts, which constitute a pyramid structure. Two of these struts are capable of rotation about a com mon axis at their points of connection to the aircraft, while the third is capable of folding about some central point. The folding is effected by a fluid-operated jack which is carried entirely on this strut. In the illustration overleaf the jack A is mounted at right angles to the strut when this is in its extended position, and the two parts of the strut are pivoted at BB to the jack cylinder. The strut is also connected by links CC to the jack plunger. Extension of the jack, therefore, folds the
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