Patent GB-465571-A (GB)
Title: Improvements in and relating to aeroplanes having adjustable pitch air-screws
IPC: E01B3/18
Filed: 1936-11-11
Abstract: 465,571. Variable-pitch airscrews. JUNKERS FLUGZEUG-UND MOTORENWERKE AKT.-GES. Nov. 11, 1936, No. 30785. Convention date, Nov. 12, 1935. [Class 114] In a variable-pitch air screw adapted to be used for braking as well as driving, and the speed of which, is maintained automatically constant, there is incorporated a device whereby the automatic control acts to adjust the blades in an opposite direction for normal or braked fly to produce a constant speed of rotation. The propeller blades 1 are provided at their roots with pinions 14 which gear with rack members 12, 13, carried by a cross-head 11 which is connected by a rod 10 with the piston 9 mounted in a cylindrical space 8 in the hub of the propeller. This space is connected by passages 21, 22, including a collar ring 24 to a control member 26. This control member is centrifugally set by a centrifugal governor 22 acting in opposition to a spring 28 which itself may be adj usted by the hand wheel 30. With normal running of the propeller, the governor and spring are in equilibrium, so that the control 26 closes the passages 21, 22 and the pitch of the blades remains constant. On variation from the desired speed the control member 26 goes up or down to open 21 or 22 to the pressure side of the pump system. Control member 26 is connected by a central pipe 41 and outside pipes 42 with a second control member 36 having pipe connections 43, 44 with a gear wheel pump 40. The gear wheel pump system includes also a reserve reservoir 45 and a byepass valve 46 whereby, with the engine cut out, a control of the blade pitch may still be effected. The purpose of the control member 36 is to change over the suction and delivery passages 43, 44 when forward running is departed from and braking is required. This setting may be effected by a hand lever 61 or there may be a conjoint control with a lever 54 which operates the engine throttle 55, and to this end the lever 54 is linked to a cam surface 51 arranged so that the change over from forward to reverse running can only be made when the throttle is set for idle running of the driving motor. In a modification instead of switching over the circuits the gear pump 40 may be arranged to be driven in a reverse direction and for this purpose the shaft 67 is provided with a bevel wheel 68 which can be made to mesh with the bevel 66 or 66<1> on a pump driving shaft 65 connected to the engine. A sliding motion of this compound bevel is effected by a rod 69 having roller contact with the cam 51 on the control lever 54. In another construction, a reversible electric motor 90 driving the pitch changing shaft 76 through gears 91 is coupled by commutators 97 and leads 94, 95, 96 with parts of the contacts 101, 102. These contacts 101, 102 take the place respectively of the control valves 26, 36 of the arrangement shown in Figure 1. In another construction, there is provided between a constant direction motor 70 and the gear operating shaft a reversing gear 74 which is controlled by a rod 82 having a sleeve 83 that is movable by a pivoted arm 85, this arm 85 carries a slotted member 87 in which one end of the lever 88 is movable, the other end being operated by the centrifugal governor. At an intermediary position the rod 88 is adjustable by means of the cam actuated control 51. Changes of speed result in the governor oscillating the linkage 85 about its pivot and controlling the pitch actuated gearing for forward running, and when the link 88 is set over by the cam to the opposite side similar controls of pitch are effected in the braking position of the blades. In another modification, there is interposed between the change over valve 36 and the control cam 51 a linkage 110 which is connected with an adjustable lever 61. In this case the cam 51 is coupled as before to the main control lever 54 but this in turn carries a cam 124 which actuates the throttle 120. The cam 124 is so arranged that from A to B it provides normal adjustment of the throttle, and from B to C is mainly operative on the braking position. With the subsidiary control' lever 61 set in position 121 the roller 114 is in contact with the cam 51 and the full automatic control is effected. In the second notched position 122, the roller 114 is disengaged, and the end 112 is brought against the stop 113 whereby the control 36 is in position to cut out the hydraulic control. Under these conditions, flying is normal without any adjustment of the pitch. In the third setting 123 the reversing valve 36 is definitely moved down to the first reversing position.