| 摘要 |
<p>A cylindrical oil-filled casing (2,3,5) has an input shaft (12) on which are mounted a pair of braking rings (17,26) which are allowed limited axial and circumferential movement with respect to one another. The ring (26) is driven by the shaft and drives the other ring (17) through a circle of angularly-spaced, spring-biased balls (28) mounted in tear-drop shaped recesses in the opposed faces of the rings (17, 26). Each ring has a frusto-conical braking rim extending parallel to a frusto-conical braking surface (8,9) provided on the casing part (5). The rims of the rings (17,26) have angularly-spaced, shallow, chordal segments removed to provide recesses which, during rotation of the shaft (12),pump oil between the braking surfaces of the rings and the casing, to form hydraulic cushions therebetween. Reversal of the shaft torque causes the balls (28) to force the rings (17,26) apart and into braking engagement with the casing, to check rotation of the shaft. The pumping action of the recesses diminishes during braking so that the cushions collapse and do not impair braking. <IMAGE></p> |
