Patent GB-753732-A (GB)
Title: Improvements in or relating to friction clutches
IPC: F16D45/00
Filed: 1954-01-26
Abstract: 753,732. Friction clutches. SOC. ANON. FRANCAISE DU FERODO. Jan. 26, 1954 [Jan. 27, 1953; Sept. 30, 1953], No. 2432/54. Class 80(2) A centrifugal or other friction clutch, between engine and synchromesh changespeed gear on a motor-vehicle transmits forward drive torque non-slip, and, by a one-way coupling, limits engine-brake overrun torque to a value below the minimum required to produce slip at the road wheels under worst conditions of adhesion. Thus limit value is greater than any value between 20 and 50 per cent of the maximum drive torque, and. preferably between 25 and 35 per cent thereof. One form uses a single driven disc having a series friction slip-coupling rendered ineffective on forward drive by a ratchet coupling; other forms use three or more driven discs, a proportion of the surfaces of which are rendered ineffective on overrun by ratchets on the driving or driven side. Figs. 1-3 show a modified driven disc for use in an ordinary clutch or (Fig. 4, not shown), in a centrifugal clutch of the Gravina type. Specification 586,910 [Group XXIV], in which centrifugal masses acting on a cam thrust-plate are mounted on a carrier electromagnetically clutchable to input for main clutch engagement and brakeable for clutch release. In this disc drive passes between the carrier disc 13 of the usual friction facings 10 and the hub 11 through a combined ratchet and slip coupling comprising a disc 22 riveted to the hub 11 and clamped frictionally between discs 15, 29, the former riveted to the disc 13, through spring washers 34 by adjusting nuts 33, to form an overload friction slip coupling. This is effective only on overrun, being by-passed in forward drive by springy facial ratchet teeth 27 pressed axially from the disc 22 for their leading edges 28 drivingly to engage undercut recesses 19 in the driving disc 15. In Figs. 5 and 7, forward drive from a facing-carrying disc 13 to the hub 11 is through spring-pressed pawls 86 pivotal'radially on discs 80. 84 riveted to the disc 13 to engage ratchet teeth 88 on the hub 1 For noiseless overrun the pawls are lifted off the teeth 88 by a drag-ring 95 having light frictional engagement at 96 with the hub 11. Overrun torque is transmitted by friction disc 92 clamped on the hub 11 between the disc 80 and a disc 91 loaded through spring-washers 94 by adjusting nuts 93. Figs. 8 and 9 (not shown) use three normal rigid driven discs, the presser- and back-plates of the first of which are driven through radial ratchets. and have a ball-bearing support on the driving flywheel so that although all six driving surfaces transmit forward drive, only three transmit overrun torque. Fig. 11, not shown, modifies this by one-way driving the front three clamping plates, the first of which has an additional friction face bearing on the flywheel, making seven forward driving faces, of which two only transmit overrun torque. Fig. 10, not shown, has three driven discs, the first rigid and transmitting both forward and overrun tcrque, the other two being as shown in Figs. 5 and 7 to transmit full forward and slip-limited overrun torque. The friction facings may be of different kind and area. The friction slip coupling may be separate from the clutch.