GB1066718A - Variable pitch propeller - Google Patents

Abstract

1,066,718. Variable-pitch propellers. G. W. KEAN, A. J. RONCARI, A. J. RONCARI, and R. A. RONCARI. Aug. 11, 1964, No. 32637/64. Heading B7V. A variable-pitch propeller, e.g. for an outboard drive, includes a hub (6) having blades 10 extending radially therefrom and rotatable thereon between positions of maximum -and minimum pitch, means for mounting the hub on a drive-shaft 49 for axial movement thereon, means biasing the blades towards a position of maximum pitch relative to said hub and means for varying the biasing force exerted by said biasing means responsive to resistance forces exerted upon said blades upon rotation of the propeller consistent with the driving torque applied to the drive-shaft. As shown, in Fig. 3a, racks 45 mounted on rack support 44 are biased by spring 42 to turn pinion portions 15 of gears 14 on the blades 10 so that the blades are biased to the maxinum pitch position. The bevelled portions 16 of the gears 14 are in engagement with a bevel gear 17 attached to a sleeve .32 which is axially slidable along a sleeve 31 pinned at (52) (Fig. 11, not shown) to drum shaft 49. Sleeves 31, 32 are coupled together at (18) (Figs. 13 and 14, not shown) in order that the hub 6 may be rotated and also to turn blades 10 to a fine pitch position. On starting, the blades are biased to the maximum pitch position which is fixed by lugs 23 engaging the end of slots (36) in collar (35) (Fig. 5, not shown). In this position, the water resistance to rotation is greatest so that torque applied to drive-shift 49 and transmitted through pin (52), sleeve 31, coupling (18) and bevel gear 17 to blades 10 overcomes the water resistance and also rotates the bevel gear 17 related to gears 14 and moves gear blades 10 to the fine pitch position. As the blades rotate towards minimum pitch positions, the pinion portions 15 which engage racks 45 likewise rotate and move the racks and support 44 axially inwardly to compress spring 42 against flange 40. With the pitch of the blades reduced, the water resistance is decreased and brought into balance with the opposing force of spring 42. When torque is transmitted to the drive-shaft 49 sufficient to completely overpower spring 42 and the blades are at the minimum pitch position a greatly increased thrust will be developed by the propeller. Before the boat responds however, the forward force thereof acts on the propeller assembly causing forward axial movement of hub 6 with respect to the drive-shaft 49. As the hub 6 is urged forward on the shaft, the parts carried thereby-the blades 10, racks 45 and the shaft 32 are also moved axially forward until there is full engagement of projections (24), (25) of coupling (18) (Figs. 13 and 14, not shown) which will further compress spring 42.