Patent GB-909693-A (GB)
Title: Improvements in clutches
IPC: F16D43/12
Filed: 1960-09-13
Abstract: 909,693. Friction Clutches. DAIMLERBENZ A.G. Sept. 13, 1960 [Sept. 16, 1959; Sept. 19, 1959], No. 31565/60. Class 80 (2). A friction disc clutch of the type having spring-loaded centrifugal masses preventing a spring-loaded pressure disc from engaging with a driven clutch disc below a certain driving speed and freeing it for engagement only above a specified speed is characterized in that the centrifugal masses are of block form and are rockable about knife-edged fulcra on straight edges thereof extending substantially tangentially to the clutch periphery, the masses being mounted in the driving part of the clutch. As shown, a clutch for a motor vehicle comprises a driving housing and gear 11, 12, 13 within which is a driven disc 19 carried by a shaft 17, masses 37 being biased inwards by springs 39 but pivoting outwardly about knife-edged fulcra 230, Fig. 3, with increasing speed to allow springs 22, 23, 33 to engage a pressure plate 44 with the clutch disc 19. The fulcra 230 engage the housing part 13. The masses 37 engage at their edges 23<SP>1</SP> with the inner periphery of the driving drum 12 and are restrained from rotating within the drum by pegs 260 engaging notches 250 in the knife edges. The knife edges may engage either a plane surface, as shown, or in V- grooves. The springs 39 biasing the masses radially inwards engage in pockets in the masses, these pockets having their ends so inclined as to form equal angles 310, 311, Fig. 4, to the normal to the clutch axis depending on whether the masses are in their inner, inoperative positions, or their outer, operative, positions. In the position illustrated, a control lever 26 allows the clutch to be substantially disengaged, the speed of rotation being such that the masses 37 are at their radially inner positions. By increasing the engine speed of a car containing the clutch, the masses 37 move radially outwards under the influence of centrifugal force and so allow the springs 22, 23 to move a disc 21 leftwards in the clutch-engaging direction. A ring- shaped slot 27 in the disc 21 carries freely rotatable pins 31 engaging cam surfaces 29, 30, Fig. 6, on a ring-shaped flange 28 fast with the driving clutch cover 11, tangentially arranged springs 33 between the clutch cover and pins 34 fast upon the disc 21 holding the rollers 31 against the cam surfaces. In the position shown, the rollers 31 engage steeply inclined cam surfaces 29, so that the tangential force of the spring 33 produces only a relatively slight axial reinforcement of the clutch engaging force of the springs 22, 23. The leftwards movement of the disc 21 so far produced acts upon the pressure plate 44 which accordingly engages the driven disc 19. The pressure plate 44 is fast for rotation with but is axially movable relatively to a disc 52 itself rotatable within the driving clutch cover 11, the disc 52 being connected for rotation with the clutch cover by tangential springs between studs 50 fast with the clutch cover and studs 51 fast with the disc 52. Engagement of the pressure plate 44 with the clutch disc 19, as described, tends to turn the pressure plate relatively to the driving clutch cover, which at this moment rotates faster than the driven clutch disc 19. Accordingly, inclined balking surfaces 45, Fig. 5, on interengaging claws 46, 47 between the axially movable disc 21 and the pressure plate 44 come into engagement, these surfaces being so shaped as to prevent further leftward movement of the disc 21. The pressure plate 44 is thus only lightly engaged with the driven clutch disc 19, the rollers 31 remaining on the relatively steeply inclined cam surfaces 29 of the flange 28 so that the axial force produced by the tangentially arranged springs 33 remains slight. On synchronization of the speeds of rotation of the driving clutch cover 11 and the driven clutch disc 19, the pressure plate 44 tends to turn relatively to the driving clutch cover so that the interengaging claws 46, 47 slide down the balking surfaces 45 into the position shown dotted at G, Fig. 5. This allows the disc 21 to move leftwards, and the rollers 31 carried thereby move off the steeply inclined cam surfaces 29 on to the relatively shallow cam surfaces 30, so that the axial force produced by the tangential clutch springs 33 is increased. This axial force is added to the clutch-engaging force of the springs 22, 23, and the clutch is now firmly engaged. If the accelerator pedal of the motor car is released while the centrifugal weights 37 are in their outward position, the car drives the engine through the tangentially arranged springs 33 without the rollers 31 lifting off the cam surfaces 30. If, however, the speed of rotation drops so that the masses 37 are moved inwards by their springs 39, the disc 21 is pushed towards the right. At first the pressure plate 44 is held in frictional engagement with the clutch disc 19 by springs 41, secured between abutment discs 40, 42 free upon bolts 16 connecting the clutch cover parts together, the abutment discs engaging flanges upon the disc 21 and upon the pressure plate 44. Slight relative rotation between the pressure plate 44 and the disc 21 engages clamping surfaces 48, Fig. 5, which press the disc 44 against the driven disc 19 to retain the clutch sufficiently firmly engaged to transmit drive to the engine for engine braking. For complete disengagement of the clutch, the control lever 26 can be operated to slide a thrust sleeve 25 and a thrust bearing 24 to the right of Fig. 1, thus withdrawing the disc 21 to the right. To prevent racing of the car engine when the clutch is only lightly engaged, the balking surfaces 45, Fig. 5, being in engagement as described above, a lost-motion device 58, Fig. 1, and a spring 56 are connected between the accelerator pedal 57 and the clutch control lever 26, the arrangement being such that depression of the accelerator pedal beyond a specified point, say one third open, tensions a spring 56 which acts through the clutch control lever 26 to reinforce the clutch-engaging action of the springs 22, 23, 33, &c.