GB522321A - Improvements in and relating to centrifugal friction clutches for a supercharging compressor on an aircraft engine - Google Patents

Abstract

522,321. Friction clutches. AEROTECHNIC DEVELOPMENTS, Ltd. Dec. 28, 1938, No. 37582. Convention date, Dec. 24, 1937. [Class 80 (ii)] In a friction clutch arranged between ar aircraft engine and it: supercharger wherein a pair of shoes 11 are centrifugally engaged with a drum 21 gearec to the supercharger anc are self-tightened during drive, each shoe i: pivoted at its trailing end 01, beyond the friction surface, to a link 10, the trailing end 02 of which is pivoted between a pair of plates 1 geared to the engine, and the link 10 lies at an angle of less than 90 degrees with the radius at the point 01 and is substantially perpendicular to the radius at the point 02. Springs 15 also urge the shoes towards engagement, while disengaging means are adapted to act on the leading ends of the shoes. In the form shown in Fig. 2, one arm 14 of a lever pivoted at 3 between the plates 1 carries a pin 13 engaging with clearance in an aperture in the leading end of each shoe, while the other arm 28 coacts with a cam 26 journalled in and held axially by the plates 1. The cam is internally threaded to engage an externally-threaded spindle 30 which is freely rotatable and which is movable longitudinally under the control of a double-acting hydraulic motor, the spindle 30 being internally threaded to engage an externally-threaded spindle 31 which is fixed relatively to the plates 1. With the cam in the position shown, the clutch is able to engage centrifugally, each shoe engaging first at its leading end and then along its whole length, followed by a self-tightening action. On operating the hydraulic motor so as to turn the cam 26 anticlockwise relative to the plates 1, the levers 14, 28 are operated so as positively to withdraw the shoes, the portions C of the cam which engage the arms 28 in the clutchdisengaged position being circular arcs so as to maintain disengagement. During disengagement, projections 47 on the shoes 11 and links 10 abut so that subsequently the shoes and links turn as a whole about the pivots 02. In the form shown in Fig. 3, the leading end of each shoe is loosely pivoted by a pin 50 engaging a slot to an arm 51 which is pivoted at 52 between the plates 1 and which has its inner end formed as a toothed quadrant 53 meshing with a pinion 54 formed on a shaft 55 journalled in the hubs of the plates 1. A cylindrical casing 57 secured to the hub of one plate 1 has a fixed diametral partition 60, Fig. 5, in which is journalled a hub 61 integral with the shaft 55 and carrying two opposed vanes 62. Liquid under pressure is supplied to either of two ducts 80 and 81 and is exhausted from the other, under the control of a cock, the ducts 80 and 81 being in communication respectively with channels 70 and 71 in the vanes 62. Thus, if liquid is supplied to the duct 80 it enters the compartments 74 of the casing 57 and moves the vanes 62 to the position shown in Fig. 5, thereby allowing centrifugal clutch engagement. If liquid is supplied to the duct 81, it enters the compartments 75 and turns the vanes 62 so as to withdraw the shoes 11. A plunger 85 slidable in the shaft 55 has a head 87 which is splined in the hub of one plate 1 and which has internal teeth 89. The plunger is urged to the left in Fig. 3 by a spring 86b tending to bring the teeth 89 into engagement with the teeth of the pinion 54 so as to lock the clutch. Fluid pressure in a channel 86, communicating with the duct 81, urges the plunger to the right to unlock the pinion 54, but a fall in the fluid pressure allows the spring to act to lock the clutch. The vanes 62 may alternatively be rotated by fluid pressure only in the direction for clutch disengagement, being rotated in the opposite direction by the centrifugal movement of the shoes.