GB910747A - Improvements relating to lever operating mechanism particularly adapated for vehiclebraking systems - Google Patents

Abstract

910,747. Vehicle brakes. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 27, 1959 [March 4, 1958], No. 6945/58. Class 103 (1). [Also in Group XXIV] In a lever-operating mechanism, for example for vehicle brakes or electrical switch gear, the mechanical advantage is automatically increased on a predetermined increase in resistance to movement. In Fig. 1, an actuating lever 1 pivoted on a shaft 2 is connected by a link 3 to one end of a lever 4 having its midpoint connected to an output member comprising an hydraulic cylinder 5, and its other end connected by a link 6 to a follow-up member 7 which is also pivoted on the shaft 2 and is normally urged by a spring 8 into contact with the actuating lever. Initial depression of the actuating lever against a low resistance will cause the lever system to move as a whole, but on increase of resistance the force of spring 8 will be overcome and a stop 11, which normally holds a spring-loaded pivoted rack 13 out of engagement with a pawl 14 on the member 7, will be caused to slide down an arm on the member 7 by virtue of a connection with a lever 10 integral with the actuating arm, so that the pawl 14 engages the rack 13 and holds the member 7 stationary, thus increasing the mechanical advantage of the lever 4. The lever 1 is returned under the action of a spring 16. In Figs. 2 and 3, an actuating lever 1 is keyed to a shaft carrying sun-wheel 21 and a disc 24 having a projecting lug 25, which is urged by a spring 36 into contact with a lug 26 of an annulus 23 rotatable in a casing 32. Providing the resistance through the system is less than the force of the spring 36, the sunwheel 21, annulus 23, planet wheels 22 and a planet carrier 28, connected to an output lever 27, move as a whole, but with increasing resistance the spring 36 yields, the lugs 25, 26 move out of contact and a pin 33 on the disc 24 allows a spring-biased pawl mounted on the annulus 23 to engage ratchet teeth 31 in the casing and hold the annulus against rotation so that the epicyclic train increases the mechanical advantage of the system. Releasing the actuating lever will allow the disc 24 to rotate and cause the stud 23 to disengage the pawl from the rack and allow the gear to return to its initial state as a solid unit.