Patent GB-978513-A (GB)
Title: Friction engaging device
IPC: F16D27/105
Filed: 1962-01-10
Abstract: 978,513. Electromagnetic friction clutches and brakes. WARNER ELECTRIC BRAKE & CLUTCH CO. Jan. 10, 1962 [Jan. 24, 1961], No. 1000/62. Headings F2C and F2E. A clutch or brake comprises a freely floating split ring 25 radially pressed outwardly or, as shown, inwardly into engagement with opposed, radially converging friction surfaces 27, 28 of spaced, relatively rotatable clutch or brake members, such as 10, 11, by a helical resilient coil 30, one end of which is anchored on one clutch or brake member 10 or 11 and the other end turn 32 of which is free and electromagnetically engaged with and disengaged from, the other member 11 or 10, so as to be expansively or, as shown, contractively wound and unwound, and the cone angle, with the clutch or brake axis, of the friction surface, 27, adjacent the free end of the coil is smaller than the opposing surface, 28, so that on winding up the coil by electromagnetic pilot engagement with the member 10 initially the frictional torque at the surface 27 exceeds that at the surface 28 to cause the split ring to be turned relatively to the anchored end of the coil and exert on the coil a frictional torque acting in the same direction as that exerted by the member 10 to augment the latter and correspondingly increase the torque winding up the coil and the radial engaging force acting on the split ring. The ring 25 is of metal or brake-lining material. The surface 28 is preferably flat and disposed in a plane normal to the axis and the ring 25 is V-shaped. To ensure clutch release, when the ring is of ordinary brake-lining material, the angle between the surfaces 27, 28 should be between 30 degrees and 50 degrees, preferably 45 degrees. The ring 25 is of metal or brakelining material. The surfaces may alternatively be curved. As shown, the surfaces 28, 27 are formed respectively on a driven member 11 and on a driving V-belt pulley 10 mounted on the member 11 by a journal and thrust bearing 23. The pulley 10 comprises inner and outer parts 17, 18 magnetically separated by a convergent ring 19, of non-magnetic material such as copper, brazed thereto. Surfaces 38, 39 on the pulley adjacent the narrow end of the ring 19 form pole surfaces and the driving element of an electromagnetic clutch having a stationary winding 43 and a core 44. The free end turn 32 of the coil 30 is cranked at 37 for axial separation and constitutes the armature and driven element of the clutch. The driven member 11, which may be of non-magnetic metal or plastic material, comprises a clutchsurrounding flange 24. The outer periphery of the split ring 25 may be wholly cylindrical (Fig. 9, not shown) or, so that the turns of the coil are engaged and disengaged successively, part cylindrical at 31 and part conical at 29 with its smaller diameter adjacent the anchored end of the coil. The part 29 is coned about 10 degrees and starts at about the second turn of the coil. The end turn 33 of the coil, cranked at 48, 49 for axial separation, passes through a window 54 in the member 11, wraps round the member 11 against the inner wall of a groove 55, and is anchored by a hook 58 thereon snapped into a slot 59. The edges of washers 56 retained by screws 57 loosely retain the end turn 33. The wrap-around of the end turn 33 provides a capstan action to reduce tension on the hook 58. In the embodiment shown, to accommodate inward shift, and distribute over a substantial arc edgewise bending, of the end turn 33 between the anchor and the window, the surface of the inner wall of the groove 55 is cylindrical from the anchor for about a half revolution, then is inwardly spiral to a ledge 63 beyond the window.