Patent GB-1242840-A (GB)
Title: Load brake for unidirectional or bidirectional use
Inventor: ARNOLD CARTER HERBERT
IPC: F16D55/30
Filed: 1970-05-14
Abstract: 1,242,840. Load-arresting brakes; multi-disc disc brakes; cooling. C. H. ARNOLD. 14 May, 1970, No. 23384/70. Heading F2E. A brake for acting on a shaft 20, Figs. 2 to 4, mounted partly in a housing 43 and rotated in one direction (e.g. clockwise, Fig. 4) against a load by a driving element 21, comprises a first cam member 25, Fig. 6, engageable with the driving element, and a second cam member 35 rotatable relative to the shaft 20, these members being formed with camming surfaces 36, 37, Figs. 2 and 6, respectively, which engage on rotation of shaft 20 in the opposite direction, so as to shift one of the cam members (e.g. 35) axially of the shaft to engage a friction brake member 42, carried by the housing and fixed against rotation relative thereto, and thereby stop the shaft. Falling, e.g. of a hoist load, is thereby checked. As shown, the brake is a disc brake and consists first of a drive shoe 41, Figs. 2 and 3, having a sleeve portion 40 surrounding shaft 20 and secured thereto by a pin 29; next, the brake member 42 connected to housing 43 and having side walls 51, 52, each surrounding shaft 20 but well spaced (at 61, 62) therefrom, and joined at the top by a top wall 53; and lastly a pressure ring 60, bonded, through a silicone rubber cushion 58, to a flange 57 of the second cam member 35. Thd second cam member 35 is slidable and rotatable on sleeve 40, while the first cam member 25 is secured to shaft 20 by the pin 29. In operation, when driving element or pulley 21 is being rotated, a pressure pad 28, Fig. 6, on pulley 21, engages a driving dog 30 on first cam member 25, thereby rotating shaft 20, which rotates a rope drum 18, Fig. 3, through gearing, to raise a load (scaffold 10, Fig. 1, not shown). At the same time, pad 28 engages dog 31, located on the second cam member 35 radially outside dog 30, whereby member 35 is also rotated, and camming surfaces 36, 37 are kept apart as shown in Fig. 2; the brake is thereby maintained disengaged. If driving of pulley 21 ceases, shaft 20 is urged counterclockwise by the load (a sleevebearing 23 carried by the shaft now slipping, within pulley 21), cam member 25 rotates counterclockwise with it, surfaces 36, 37 engage, and cam member 35 is forced axially against brake member 42, which is in turn forced against drive shoe 41, springs 47 on pins 46 (connecting member 42 to housing 43) being compressed. The brake is thus applied. To enable the load to be lowered positively, under power, a further pressure pad 27, Fig. 6, is provided, so that when pulley 21 is rotated counterclockwise, it is pressure pad 27 which engages both dogs 30, 31, whereupon the surfaces 36, 37 are separated, tending to release the frictional load on brake member 42. The brake thereupon slips and the loaded shaft urges the surfaces 36, 37 towards each other again. The effect of this is that the load is driven downwardly against reduced friction on the brake. If driving ceases the brake is again automatically engaged. As shown, the drive shoe 41 is furnished with an annular pressure plate 49, while brake member 42 is furnished with brake linings 50, 56. For cooling purposes drive shoe 41 has radial ribs 66, while walls 51, 52 of member 42 are mutually spaced, are flared at 63, 64, for upward air circulation, and are ribbed at 65. In Fig. 8 (not shown), cam members 25, 35 each have two oblique cam surfaces, and there are other modifications, to allow operation, as first referred to above, selectively in either direction of rotation. The device of Figs. 2 to 6 is depicted in connection with a one-way acting hoist (Fig. 1, not shown), while that of Fig. 8 in connection with a two-way hoist (Fig. 7, not shown).