GB480474A - Improvements relating to screw propellers - Google Patents

Abstract

480,474. Screw propellers. PARAL, J. Dec. 24, 1936, No. 35400. Convention date, June 23. [Class 114] In screw propellers the boss is continued as a cylindrical member to project within the hull of the vessel and it is provided with passages open to the inside of the vessel and within which the pitch varying mechanism is disposed. The cylindrical root 6 of the blade is provided with eccentric pins 7, 7a which are coupled by rods 8, 8a, disposed in passages 3 within the hub 4 and its cylindrical extension 2, to eccentric pins 9, 9a upon a disc 10 which has a worm-wheel thereon engaging a worm 13 which is adapted to be operated by an electric motor or other means. In an alternate form there is provided on the blade root a pinion gearing with a rack which in turn gears with an intermediate pinion having a second pinion thereon which actuates a second rack finally driving a pinion upon the shaft which carries the worm-wheel 10. For the purpose of actuating the worm 13 its shaft carries a bevel 17 engaging a bevel 18 on a shaft which also carries a pinion 21 geared to a pinion 27 on a free sleeve 27a encircling the shaft 1. When the sleeve 27a is braked by a band-brake 30, power is obtained from the shaft for adjusting the blade pitch. Blades are stopped at the outer two end positions for ahead and stern running by releasable ratchets, the pawls 15, 15a of which engage the ratchet wheels 14, 14a. The ratchets carry projections 15<1>-15<1>a which are engaged by a projection 32 which is moved parallel to the shaft 1. When the blades reach their designed end possible pitch setting, further rotation is prevented by engagement of a rib on the blade root with ribs on the boss, whereupon the band-brake 30 slides on the sleeve 27a and accidental further rotation is prevented. Where power is used for one direction of adjustment during such movement, a strong spiral spring 23 is adapted to be wound, such spring being secured at one end to a frame 26, and at the other end to a sleeve 22 coupled to the gearing wheel 21. This spring becomes operative when the related ratchet pawl is released for moving the adjusting gear in the opposite direction.