Patent GB-636241-A (GB)
Title: Improvements in apparatus for transmission of movement
IPC: B64C11/36
Filed: 1940-03-12
Abstract: 636,241. Variable-pitch propellers. FORGE ET USINAGE METAUX LEGERS. March 12, 1940, No. 4637. Convention date, April 19, 1939. [Class 114] [Also in Group XXIV] A change-speed gearing comprises gear 8, 9 respectively loose and fixed on a driving shaft 1 and several pairs of pinions on shafts parallel to the shaft 1 and meshing the gears 8, 9, the pinions of each pair being adapted to be clutched together. The tooth numbers of the pinions of each pair differ slightly from the tooth numbers of the corresponding pinion of the other pairs so that depending on the pair of pinions which are clutched together the gear 8 rotates faster than, at the same speed as, or more slowly than the gear 9. As applied for controlling the pitch of the blades of a screw propeller the blades 3, Fig. 1 are rotatably mounted on a sleeve 2 on the driving-shaft 1 and have worm-wheels 4 which co-operate with worms 5. A stationary casing 12 supports six pairs 10a, 11a ... 10f, 11f of pinions which have different numbers of teeth and mesh with the gears 8, 9, the gear 8 meshing also with pinions 6 on the shafts of the worms 5. The pairs of pinions are provided with clutchdevices, described below, for coupling together a selected pair. When a pair 10a, 11a ... 10d, 11d is coupled, the gearing rotates the blades at such rates that a slow increase, a slow decrease, a rapid increase, or a rapid decrease of pitch respectively is imparted. The pinions 10f, 11f have tooth members such that when coupled the gears 8, 9 rotate at the same speeds. This pair is normally clutched when the others are de-clutched. The clutch-devices 25 for the pairs of pinions are selectively operated by levers 23 co-operating with cam-slots 22 in an annulus 21 revolubly mounted in the casing 12 and geared through a pinion 28 and rack 29 for moving the annulus 21 anticlockwise. The rack is connected to a piston 30 mounted in a cylinder 40 and co-operating with another piston 31 provided with springs 32, 33. The piston 30 co-operates also with a stop 35 on a piston 36 mounted in a cylinder which communicates with the cylinder 40. An identical set of members 28<SP>1</SP>, 29<SP>1</SP> ... 40<SP>1</SP> (not shown) is provided for moving the annulus 21 clockwise. When the cylinder 40 is connected to a mediumpressure fluid supply, the piston 30 and rack 29 are depressed, the movement being limited by the stop 35, and by contact of a part 39<SP>1</SP> of the piston 30<SP>1</SP> with the piston 31<SP>1</SP>, annulus 21 receives a half-shift anticlockwise movement, and one of the cam-slots 22 effects engagement of one of the clutches. When the cylinder 40 is connected to a high-pressure fluid supply, the stop 35 is withdrawn, the piston 30 and rack 29 are fully depressed, the movement being limited by contact of the piston 31<SP>1</SP> with the top of the cylinder 40<SP>1</SP>, the annulus 21 receives a full-shift anticlockwise movement, and one of the cam-slots effects engagement of another clutch. Similarly, when the cylinder 401 is connected to a medium or high-pressure fluid supply, the annulus 21 receives a half or fullshift clockwise movement to control the clutches. The above-described clutch-controlling device may be replaced by electromagnetic means. A pitch-indicating device is driven by a toothed wheel 20 which is controlled by the pinions 10e, 11e through differential gearing comprising planet-wheels 17, 18 mounted on a carrier 16 and engaging pinions 14, 15 connected to the pinions 10e, 11e respectively, the planets 18 co-operating also with the wheel 20 and the planet 17 with a fixed annulus. If the gears 8, 9 rotate at the same speeds then the pinions 10e, 11e have the same speed as one another, but when the pitch of the blades is adjusted, the pinions move relatively, and the wheel 20 is moved to adjust the indicator. For automatically limiting the adjustment-movements of the blades, the clutch-levers 23 co-operate with adjustable abutments on an annulus 41 gearing with a pinion 42 which can be clutched to the pinion 20. For moving the blades into feathering position if the engine fails, the pinion 10d of the pair which when clutched together give a rapid pitch decrease gears with a pinion on the shaft of an electromotor which may be energized from an electric battery.