Patent GB-1448309-A (GB)
Title: Automatically compensating brake linkage actuator device
IPC: F16D65/56
Filed: 1974-07-16
Abstract: 1448309 Brake transmitting mechanism; slack &c adjusting KNORR-BREMSE GmbH 16 July 1974 [23 July 1973] 31527/74 Heading F2E A brake-linkage actuator device with provision for automatic length compensation comprises an axially-displaceable adjusting spindle 26 adapted to be coupled non-rotatively for force transmission to the linkage (not shown), an actuator sleeve 7 coaxial with the spindle and non-rotatable relative thereto, a threaded coupling nut 22 in engagement with a non-self-retarding thread 25 on the spindle and arranged to transmit a brake-apply force to the spindle when the actuator sleeve 7 is displaced in the brake-apply direction (leftwards, as shown), the engagement of the coupling nut being such that the nut is movable relative to the spindle when a net axial force is applied to the nut or the spindle for compensatory lengthadjustment, two rotary couplings 20, 24 and 21, 23 respectively, of which (at least) one is adapted to be actuated when the nut undergoes axial displacement, a control sleeve 28 movable between limit stops 16, 37 and urged towards engagement with the coupling nut 22 (i.e. in the brake-apply direction) by spring means 34 through a stop clutch 30, a first stop 17 fixed in the actuator device and engageable rotatively (e.g. by bearing 35) by that end of the spring means 34 remote from the sleeve flange 29, and a second stop 33, also engageable by the spring means 34 and located rearwardly of the first stop with respect to the brake-apply direction when the actuator device is in the non-actuated state. The device is double-acting in the sense that it will compensate automatically when the application stroke of the linkage is too small as well as when it is too large. However, the device may be rendered single-acting (for large strokes) by providing a series of axially-extending projections 43 at one end of control sleeve 28 which engage recesses 44 in members 11, 12 associated with the first ("spring") stop 17, the sleeve being thereby rendered non-rotatable. Preferably, means for resiliently biasing the adjusting spindle 26 in the brake-apply direction are provided, comprising a compression spring 41 located between a piston 2 secured to actuator sleeve 7 and a non-rotatable guide ring 40, a fixed pressure stop 15 for arresting the guide ring after its movement by the spring 41, and an adjusting nut 38 threaded on the adjusting spindle; the nut 38 is rendered non-rotatable when it is engaged by a stop 39 formed on the guide ring 40 but is rotatable when it engages stop 15; a bulge 42 is provided on guide ring 40 so that when it is in contact with pressure stop 15 the axial clearance between stops 15 and 39 is greater than the thickness of adjusting nut 38. If the linkage is required to perform large strokes whereas the length of the device must be kept small, the front limit stop 37 for the control sleeve may be displaceable against the action of a biasing spring (Fig. 2, not shown). Fig. 3 (not shown) depicts a modification of the device associated with an "H" brake linkage. In this case the second "spring" stop 33 is not located rearwardly of the first "spring" stop 17 with respect to the brake-apply direction in a structural sense but is rendered functionally so by replacing an annular member 36, Fig. 1, by a tubular member (36<SP>1</SP>) having an internal flange at one end to engage stop (17<SP>1</SP>) and an external flange at the other end to engage stop 33. The device is intended for rail vehicle brakes.