Patent GB-499634-A (GB)
Title: A regulatable screw propeller having adjustable blades
IPC: B64C11/36
Filed: 1938-04-14
Abstract: 499,634. Screw propellers. TRIGGS W. W. (Argus Motoren Ges.) April 14, 1938, No. 11543. [Class 114] In a variable-pitch screw propeller a source of power drives a gear which can be connected to either one of two gears for increasing or decreasing the pitch of the blades under the action of a speed governor which controls the coupling of the gears with the driving gear and there.is provided positive adjusting means for the governor and also positive stop means for discontinuing the drive. A windmill 4 with blades 5 of slightly negative pitch is secured to a shaft 3 upon which are freely mounted bevel wheels 9, 10, which are connected by a bevel wheel 11. Keyed to the shaft 3 is a two-sided coupling 7 having dogs 7a, 7b respectively, adapted to engage dogs 9b, 10f upon the bevel wheels 9, 10. A centralizing spring 8a is employed between this coupling and the two bevel wheels. The coupling is secured to a rod 7c which at its forward end has a ball and thrust connection with a rod 32 which is in turn connected to a piston 13 in a cylinder 12, this piston being restrained by springs 14, 14a. The drive from either wheel 9, 10, when the coupling is engaged is communicated by a pinion 10g through a train of gears to a worm wheel on the root of the propeller blade. Movement of the hydraulic piston 13 is effected automatically by means of a centrifugal governor 21 which sets a controlling valve 19 in the pipes between the hydraulic cylinder 12 and the oil pump of the engine. When speed increases or decreases, this control valve moves up or down to direct fluid pressure to one side or the other of the piston 13 whereby the coupling 7 is moved to the required position to engage with one or other of the bevel wheels 9, 10. The rod 32 has a sleeve 32a which co-operates with a pivoted lever 30, and when the outer end of this lever contacts with stop 31 or stop 44 on the blade root representing maximum and minimum pitch setting of the blade, the rod 32 is moved so as to disconnect the coupling. 7 and prevent over setting of the pitch. Beneath valve 19 is located a spring loaded disc 43, and this is connected by a channel 37 and pipe 35 with a hand pump 34. When it is required to set the blade, either with the engine stationary or running slowly to a full feathering position, the hand pump 34 is operated for producing a higher pressure and forces up the member 43, so that the control valve 19 is held in its uppermost position. At the same time pressure fluid passes through the open ports to the cylinder 12. The setting of the governor may be effected by rod 26a operating through cam 20 upon a movable cap at the end of the governor spring. In a modification, the hydraulic control is single acting and the piston is provided with side openings into which at various positions a hydraulically operated stop pin may enter. In a modification, the driving bevel wheel 71 is fitted directly to the shaft 58 on the windmill 60. The cross shaft carries the two bevels with which the slidable coupling 64 is connected. The coupling is directly attached to a shaft and is movable endwise under the centrifugal control of a weight 65 thereon, acting in opposition to a spring 62. The end of the shaft is in contact with a pivoted lever 96 which in turn contacts with a member 93 mounted slidably in the hub and adapted to contact with control stops 88. The driven worm wheels 77 may be adjustably mounted on the blade roots and also the corresponding worms 76 may be secured to shafts which are adjustable endwise and may be spring restrained, whereby the lining up of these gears can be effected readily. In one form of stop mechanism, a sliding member 93 in a sleeve 92 is under spring restraint 94, and when contacting with a stop member 88 on the blade root is adapted to be moved so that as the lever 96 is moved, the shaft 63 carrying the coupling member is also moved to uncouple the drive. At the same time the outer sleeve 92 operates a bell-crank lever 102 having a ratchet nose connected with a ratchet 100 on the lever 96 for the purpose of locking it. Normally, the shaft 63 and coupling are maintained in central position by means of a spring pressed ball entering a cup 97 in the shaft. Instead of the centrifugal weight being carried directly by a transverse driving or coupling shaft, the coupling is moved through a pivoted crank lever, the .outer part of which is weighted at 108 and restrained in its normal position by a spring ball 108a. The crank lever is continued to co-operate with an abutment on 107 which is under the control of two springs 113, 114, one spring acting directly on the lever and the other upon a cup controllably mounted on the lever. By movement of a rod 116, a flange 117 thereon engages the cup 112 and frees the lever from the spring 114. This provides for two spring settings for the governor and therefore for two speed settings of the propeller. The device for freeing the coupling is a bell-crank lever 131 one arm of which contacts with the stop rod 126 and the other with the pin 104a on the coupling.