Patent GB-441050-A (GB)
Title: Improvements relating to variable pitch screw propellers
IPC: B64C11/34
Filed: 1935-07-05
Abstract: 441,050. Variable - pitch screw propellers. ALLGEMEINE ELEKTRICITATS GES., 2, Friedrich Karl-Ufer, Berlin. July 5, 1935, Nos. 19318, 19319, 19320, 19321, and 19322. Convention dates, July 5, 1934, Aug. 23, 1934, Dec. 8, 1934, Dec. 8, 1934, and Jan. 24, 1935. [Class 114] In a variable - pitch screw propeller, adjustment of the blades is effected as the result of a change of form of an adjusting member consequent on the supply of heat energy to it. The screw propeller blades 2 are supported in a boss 1 so as to be rotatable on their axes as the result of the pins 7 in the roots thereof being moved by a U- shaped bi-metallic element 8 to which heat is supplied by electrical energy to an embracing coil 10, the terminals 12, of which are connected to a source of electrical energy through brushes 13 and a switch 14. In some cases, more than one element 8 is provided for each blade. In order to conserve the heat, the inner surface of the boss is pro - vided with an insulating layer 17. Instead of being U-shaped the bimetallic element may be of strip, spiral, or conical form, and a number may be employed in series so as to multiply the effective control. In a modification, the electrically heated member takes the form of a bellows 19 filled with a fluid having a high coefficient of thermal expansion. Into this bellows projects a tube 20 carrying a heating element 21. One end of the bellows is connected at 7 to the blade and the other end has an abutment against a fixed surface. In addition to this heating device, a further cooling device may also be employed, such device consisting of one or more valved orifices 29, 30 through which air is conducted to the adjusting member, and such air valves 31, 32, may be actuated by electromagnets 33, 34 arranged in the circuits of the heating current. In connection with these air intakes, the inner wall of the bellows may be provided with deflectors which direct the current to the heated adjusting member. Instead of coupling the bellows direct to the pin 7 it may abut against a slidable member having slots which in turn engage the pins on the blade roots. Live or exhaust fluid from the driving motor may be employed as the heating agent. In the case of internal combustion engines only the exhaust gases are used for heating purposes, and for this purpose a passage 86 is connected with the exhaust pipe and the gases are admitted under the control of a valve 89 to a chamber in which is placed the bellows 83. This bellows has a fixed abutment 82 and its free end contacts with a slidable member 80 which has a link connection with the blade roots. The passage 86 is prolonged and enlarged at 87 to form an intake for cooling air which is admissible also under the control of the valve 89. Both the heating and the cooling gases pass over the bellows and exhaust through the opening 88. In another modification, alternate metallic sleeves 90-98 are disposed around a control rod 99, the last element 98 being secured to this rod, and the first element abutting against a fixed surface 94. In this case, the actuating rod 99 has slots which engage pins 102 on the roots 103.