Patent GB-1377917-A (GB)
Title: Compensated braking system
IPC: F16D63/00
Filed: 1973-07-23
Abstract: 1377917 Braking systems; disc brakes; external shoe brakes INVENTIO AG 23 July 1973 [26 July 1972] 34916/73 Headings F2E and F2F A braking system for braking a rotating shaft. 1 of a conveyer system such as a passenger conveyer belt escalator comprises a first brake means including a first brake element 3 rotatable with the shaft 1 and retardable by a second brake element 5 which itself is retardable by a second brake means; the element 5 is-urged into frictional contact with element 3 by the action of springs 8 but the system also includes means to relieve this frictional contact which means comprises an intertial element 12 mounted on the shaft 1 to be relatively rotatable thereto and carrying camming means 12.2, and cam following means 14, which are resiliently urged into contact with the camming means 12.2 and which counteract the springs 8 in dependence upon the relative angular displacement of the camming means 12.2 and the cam following means 14 about the axis of rotation of the intertial element 12. The first and/or second brake means may be internal shoe brakes, external shoe brakes or bond brakes. However in the embodiment of Figs. 1, 2, the first brake element 3 is a carrier disc of a disc brake and the element 5 is in the form of a disc displaceably mounted on disc 3 and formed with pads 6, 7. A pressure disc 4 displaceably mounted on disc 3 is actuable to clamp disc 5 between itself and disc 3 by the action of springs 8, which are arranged on spring rods 10.  The camming means 12.2 comprise three setting cams with curved surfaces in the form of an equilateral triangle. The cam following means 14 comprise rollers rotatably mounted on respective angle levers 13 which are rotatably mounted in a bearing block 17 secured at the carrier disc 3. The lever 13 receives a turning moment from a spring 15 and a pin 16 engaging the pressure disc 4 is mounted a small distance from lever 13. The second brake means comprises a disc brake with stirrup 19 having two forked levers 19.1, 19.2 provided with brake pads 22, 23. A compression spring 20 acts to close the stirrup 19 and the stirrup is spread by an electrically operated clearing device 21 comprising a wedge 21.1 acting on rollers 19.11, 19.21 arranged. on the levers 19.1, 19.2. During starting up of the conveyer system the second brake means in cleared by the device 21 and the carrier disc 3 and the inertial element 12 are brought to synchronous rotation. In the event of braking of the system by interruption of the current to device 21, brake disc 5 is retarded and the discs 3, 4, are also retarded. However the inertial plate 12 endeavours to maintain its rate of rotation and a relative displacement occurs between the carrier disc 3 and -the plate 12 proportional to the braking retardation and also to the loading moment of the conveying system. This displacement causes displacement of the lever 13 which is pressed against pin 16 to diminish the braking moment of the first brake means in dependence upon retardation or load.  In the embodiment of Figs. 3, 4 a T-shaped brake disc 26 is provided and the second brake means is in the form of an external shoe drum brake with brake shoes 27, springs 29 and a cleaning device 31. An arm 32 acts as a guide for a pressure pin 33, and the end of the pin 33 adjacent the inertial plate 34 is constructed as a bearing yoke 33.1 in which a roller 37 pressed on to setting cams 35, 36 is rotatably mounted. The setting cams 35, 36 are of fork-like construction and increase in thickness from the free tire end to the securing end.