Patent GB-416743-A (GB)
Title: Improvements in servo-brakes
IPC: B60T13/06
Filed: 1933-08-21
Abstract: 416,743. Servo-brakes. PIGANEAU, G. P., 152, Boulevard Malesherbes, Paris. Aug. 21, 1933, Nos. 23287 and 23288. Convention dates, Aug. 25, 1932 and June 13, 1933. [Class 103 (i).] A brake applied by centrifugal force by means of masses on an axle along which they displace a member to operate an internal shoe brake, is arranged with the masses 30, 30a, Fig. 1, outside the brake drum and a clutching member 18 inside the brake drum and the axle is mounted eccentrically on the supporting plate 3 of the brake and is adapted to be displaced to engage the clutching member with the drum. The clutching-member is adapted to be automatically disengaged at great braking powers. A counterbalancing-spring is adapted to yield and limits the braking power and is adjustable to take up wear. In one arrangement, direct manual operation is obtainable. The centrifugal device is contained in a cylinder 6 eccentrically mounted by bearings 4, 5 in the casing 1 so that rotation of the cylinder by means of a manually operated cable 10 on a circular part of the cylinder moves the roller 18, which drives the centrifugal device, into engagement with the brake drum 17. The manual control is by Bowden wire, the outer casing of which engages a spring to limit the manual force. The roller 18, comprising a ring of yielding material held by lateral conical surfaces between washers 19, 20 of elastic material compressed by a nut 21, and having a positive connection by a pin 22, is mounted on a tube 16 slotted to receive spring-pressed wedges 24, 25 bearing on the edges of Y-shaped members 29, 29<a>, the forks of which guide the centrifugal masses 30, 30<a> fixed to the central branches of these members. The wedge 25 engages a rod 31 engaging a lever 32 adapted to operate a two-shoe servo-brake acting on the drum 17. The wedge 24 has an extension 39 engaging a spring pressed member 40, the spring tension of which is adjustable by nuts 45, 46. Rotation of the centrifugal device causes the masses 30 30<a> to move out and press against the wedges by means of the inclined edges of the members 29, 29<a> operating the brake by the rod 31. The braking pressure cannot rise above a limit determined by the tension of the spring 43 which yields at this limit. When the spring 43 yields to such an extent as to allow the masses to engage the interior of the casing 6 and a stud 6<b> on the member 29<a> to engage a recess 6<a> in the casing 6, the casing is turned with the masses in such a direction as to remove the roller 18 from the drum 17, the masses move toward the centre away from the drum which again returns to brake position under the manual force. The casing 41 containing the spring 43 is adapted to be screwed into the casing 1 to adjust the brake. A spring 7 returns the cylinder 6 on release of the manual control. In a modified form, the cylinder 6, Fig. 7, is mounted on journals arranged eccentrically and when released by a manually controlled lever 51 engaging a projection 53 of the casing, is pressed upwards by a spring 61 to engage the roller 18 with the drum 17. On the same pivot 33 as the lever 51, is a lever 32 operated by the rod 31 and operating a wedge 64 adapted to force shoes into engagement with the drum by means of rollers. The brake may be directly manually operated by means of a flange 63 on the lever 51 adapted to engage the lever 32. A plurality of springs 43 are used. The cylinder 6 may be held in release position by a screw 62. To prevent resistance to the operation of the device by the lubricating oil, holes 70, 72 are provided through which oil is forced by centrifugal force to the outside of the casing and returns through a hole 71 when the casing returns to release position.