Patent GB-939490-A (GB)
Title: Improvements relating to friction clutches incorporating torque limitation
IPC: F16D43/21
Filed: 1960-12-02
Abstract: 939,490. Slip couplings and clutches. J. WALTERSCHEID, and B. WALTERSCHEIDMULLER. Dec. 2, 1960 [Dec. 3, 1959; Jan. 9, 1960], No. 41587/60. Class 80 (2). A friction clutch or coupling adapted to slip on overload is engaged by a negative rated spring the deflection of which is increased if the maximum desired transmitted torque should tend to increase due, for example, to an increase in the coefficient of friction of the friction surfaces, so that the engaging pressure of the spring is reduced to maintain the torque transmitted substantially constant. Fig. 8 shows a slip clutch having a driven casing 11 with a presser plate 18 axially slidable therealong and biased by a negative rated laminated annular spring 19 to engage a driving plate 10 and to engage a driving plate 9 with a backing plate 16. The driving plates 9, 10 have cam recesses engaged by balls 7, 8 mounted in a flange 6 of an input hub 1. The inner periphery of the spring 19 reacts against an extension 61 of the casing 11. The clutch slips during operation so as to transmit a desired maximum torque. If the torque transmitted increases, the balls 7, 8 ride up the walls of the cam recesses, forcing the plates 9, 10 apart and deflecting the spring 19, the pressure of which decreases to reduce engaging pressure of the clutch and thus to maintain the torque transmitted constant. The clutch is disengaged by a release bearing 69 acting on the inner ends of throw-out levers 65 pivoted at 67 to the casing 11 and pivotally mounted at 66 on extension lugs 64 of the presser plate 18. A tension spring 71 between the plates 9, 10 ensure that the clutch runs wholly free from frictional drag when the presser plate is withdrawn. Fig. 3 shows a multi-plate slip coupling having plates 21, 22 mounted on a driving hub 1 and a driven sleeve 23 which is drivingly connected to a ring 25 by balls 24. The plates 21, 22 are engaged by an annular spring 26 which reacts against the ring 25. A backing plate 28 is adjustably screwed into a driven casing 11 to prestress the spring 26 to the required value. The ring 25 is connected to the casing 11 by a torque responsive device comprising balls 29 in cam recesses in the ring 25 and a flange 16 of the casing and serve to move the ring 25 to the right to reduce the spring pressure engaging the coupling to maintain the torque transmitted substantially constant. Fig. 6 shows a coupling having a driving hub 1 in which bearing pins 44 are adjustably mounted. Recesses 48 in the bearing pins accommodate the ends of corrugated leaf springs 49 each of which is prestressed longitudinally as well as transversely. A roller 50 is engaged in a recess 51 in each leaf spring and bears against a recess 52 in a friction shoe 53 engaging a driven drum 11. If the co-efficient of friction increases during operation of the coupling the shoes will be displaced relative to the hub 1 and the rollers 50 cam the springs 51 radially inwardly, reducing the spring pressure engaging the coupling due to the negative rating of the springs. The maximum torque transmitted is thus maintained constant.