GB854786A - Improvements in or relating to the propulsion of marine craft - Google Patents

Abstract

854,786. Drive for marine variable pitch propellors. TRANSPORT EQUIPMENT (THORNYCROFT) Ltd. Oct. 28, 1958 [Jan. 14, 1958], No. 1306/58. Class 114. In a marine propulsion unit a gas turbine (not shown), disposed with its shaft vertical, drives a variable and reversing pitch propeller E via a centrifugal clutch 4, or drive shaft 6, right angle gearing 8 and 10 and a propellor shaft 9. The clutch 4 is adapted to engage when the turbine rotates above its self sustaining speed. A pressure pump, driven by the gear train 14, 15 and 16, delivers oil for the hydraulic operation of the control valve 21 via a pipe (not shown), communicating with an inlet passage 18a and an axial passage 21a. The control valve 21 is operated by load via control rods (not shown), levers 19 and a bridle 20. Oil admitted under pressure to the appropriate side of the ram 25, operating in a cylinder 26 carried by the propellor shaft 9, via the ports 23 and 24 effects an axial movement of the shaft 27 and a simultaneous angular displacement of the propellor blades 12 via the member 28, thrust block 29, pivot pin 30a and radial arm 30. If the pitch setting is altered by an abnormal load, by forcing &c., the propellors will return to the original setting automatically. Lubrication of the unit is effected by a bleed from the pressure pump to the gears 14, 15 and 16. A thrower 17, throws the oil clear of the clutch 4 on to the walls of the casing C. The oil drains downwards to lubricate the bearings of the drive shaft 6 and the bevel gears 8 and 10 and collects in the casing 7 to lubricate the mechanism contained therein, any surplus oil is withdrawn by a scavenge pump arranged in tandem with the pressure pump. A bleed from the hydraulic circuit pressurises the boss 13 to prevent ingress of water at the blades 12. The unit may be housed in a sound insulated and waterproof structure adjacent to the transom of the boat and project downwardly through a suitably sealed aperture in the bottom of the boat. It may be mounted outboard of a boat. It may work in association with a rudder or may be angularly moveable about a vertical axis under manual or power control. Twin units may be used to facilitate steering and manoeuvring. The axis of the drive shaft may be offset with respect to the axis of the turbine. In event of failure of the hydraulic system the pitch adjusting mechanism may be operated pneumatically. Specification 854,788 is referred to.