Patent GB-476750-A (GB)
Title: Improvements in friction clutches, brakes and the like
IPC: F16D43/08
Filed: 1936-06-25
Abstract: 476,750. Brakes. CARWARDINE, G. June 25, 1936, No. 17604. [Class 103 (i)] [Also in Group XXIV] A friction clutch or brake includes two elastic force units, one of which comprises a resilient member interposed directly between a movable clutch or brake member and a member to which an engaging force is applied, while the other unit comprises a mechanism which applies a rising force to the latter member as a spring is allowed to relax, so as to augment the engaging force. In the centrifugal clutch shown in Fig. 1, comprising a driven plate 6 arranged between a driving flywheel 2 and a presser plate 4 slidable in a cover 1 secured to the flywheel, compression springs 9, forming the first unit, are interposed between the plate 4 and a second plate 5 slidable in the cover. Bell-crank levers are pivotally mounted on the plate 5, one arm 14 of each being weighted at 17 while the other arm 13 has a pin 18 carrying rollers 15 engaging a ring 16 secured to the cover 1. Radially arranged tension springs 19 are connected between the pins 18 and pins 20 secured to the cover. In the disengaged position shown, the arms 13 are radially directed, that is are in dead-centre position with respect to the springs 19, so that the latter have no influence, while the springs 9 are completely relaxed. When the weights 17 move outwards under centrifugal action, the springs 19 act through the arms 13 to apply an axial pressure to the plate 15, serving to compress the springs 9 and engage the clutch. The arrangement may be such that the two units balance each other throughout the effective range of movement of the mechanism, the restraint to the movement of the weights 17 being provided by auxiliary compression springs 21 which act between the flywheel and the plate 4 and which tend to move the latter to disengaged position. Alternatively; the first unit is stronger than the second unit. The clutch may be disengaged manually through radial levers 28 acting on pins 26 secured to the plate 4. In the modification shown in Fig. 6, the second unit comprises compression springs 19a arranged between the two parts 32, 33 of telescopic struts connected through pins 35, 37 between a sleeve extension 50 of the cover 1 and a sleeve extension 38 of the plate 5. An arm 12 extending from each part 32 carries the centrifugal mass 17. In the manually-controlled clutch shown in Fig. 4, the second unit comprises arms 12 pivoted to the cover 1 and carrying rollers 15 acting on the plate 5, with radially-arranged springs 19 connected between the roller pivots and pins 20 carried by the plate 5. The clutch is engaged by moving the plate 5 by means of a lever engaging a groove. The two units being exactly balanced in all positions, the operator only has to overcome friction of the moving parts. The arms 12 are extended at 31 so as to afford balance against centrifugal action at an intermediate position of the arms 12, while centrifugal action assists in both full engagement and full disengagement. In the vehicle brake shown in Fig. 7, wherein shoes 40, 41 pivoted at 42 to the chassis and interconnected by a retracting spring 21 co-operate with a drum 39, a compression spring 9, forming the first unit, is interposed between the shoe 40 and a plate 5 which is also pivoted at 42. The second unit comprises a compression spring 19a arranged between the two parts 32, 33 of a telescopic strut connected between a pin 43 secured to the chassis and a lever 44 pivoted at 45 to a lug extending from the shoe 41. A second arm of the lever carries a roller 47 engaging the plate 5 while a third arm is connected to an operating rod 46. A centrifugally-acting brake according to the invention may be used to prevent a predetermined speed from being exceeded. Specification 377,251, [Group XXXII], is referred to.