Patent GB-1440966-A (GB)
Title: Automatic clearance regulator for braking devices in particular  for railway vehicles
IPC: B61H15/00
Filed: 1973-06-20
Abstract: 1440966 Brake transmitting-mechanism; slack adjusting WABCO WESTINGHOUSE SpA 20 June 1973 [22 June 1972] 29216/73 Heading F2E An automatic regulator 1 for radial clearance between a rotatable member 18, Fig. 1, and a braking element 17, arranged for insertion in a transmission 24, 25, between an operating device 2 and the braking element 17 itself, comprises a nut 31, Fig. 4, engaged on a screw 26 which is fixed to or, as shown, forms part of the rod 25 arranged to be connected to the braking element, means (as shown, a traction sleeve) 34a, 34b engageable with the nut 31 to prevent rotation of it but also arranged when appropriate to move it axially, the sleeve 34a, 34b, being connected to a further rod 24 arranged to be axially movable by the action of the operating device 2, and a thrust member (as shown, a bush) 42 for applying axial thrust to the nut 31, the bush 42 being connected elastically to the sleeve 34a, 34b by at least one spring 41 disposed (effectively) between the bush and the sleeve, the bush 42 being fixed (by 43, 23) to the regulator housing 21. As shown, a piston-rod 3, Fig. 1, is connected to rod 24, while the cylinder for the operating member 2 is connected to a stopping block 10, Figs. 1 and 5, a predetermined distance a between the front cover 22 of housing 21 and stopping block 10 being proportional to the normal clearance between a shoe 17 and wheel 18. In operation, with normal clearance, the regulator first moves as a whole, and front cover 22 contacts stopping block 10 at the same time as shoe 17 contacts wheel 18. If leftward movement of piston-rod 3 is continued, first the effective length of the assembly 24, 25, increased, then rod 34 acts directly on rod 25, and finally various parts of the mechanism undergo elastic deformation. With clearance greater than normal, the regulator again moves as a whole until cover 22 contacts stopping block 10, but at this stage shoe 17 is not yet in contact with wheel 18. As leftward movement of piston-rod 3 continues, rod 24 is drawn to the right relative to housing 21, entraining sleeve 34, a tubular element 37 and support ring 38, Fig. 3, and thereby compressing springs 41 until face C 2 <SP>1</SP> on sleeve 34 comes away from face C 2  on nut 31, and face C 1 <SP>1</SP> contacts face C 1 . Rod 24 now pulls nut 31 bodily to the right, and, with it, rod 25, while thrust member 42 (rigid with housing 21) remains fixed, and nut 31 through pins 47 and cap 49 compresses a spring 50, until shoe 17 contacts wheel 18. During the return stroke, as soon as sleeve face C 1 <SP>1</SP> disengages from nut face C 1 , spring 50, via pins 47 and thrust bearing 48, forces nut 31 to rotate on screw 26, thereby reducing the effective length of the regulator, until a thrust bearing 44 again contacts bush 42. With clearance less than normal, the regulator moves as a whole until shoe 17 contacts wheel 18, whereupon rod 25 stops moving. Rod 24, housing 21 and bush 42 are still free to move rightwards so bush 42 entrains nut 31 causing it to rotate in the direction to increase the effective length of the regulator until cover 22 contacts stopping block 10.