Improvements in or relating to electro-magnetically operated disc clutches or brakes

摘要

973,229. Friction clutches; operating clutches; electromagnetic brakes. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. Feb. 27, 1962 [March 7, 1961], No. 7695/62. Headings F2C, F2E and F2L. A spring-engaged electromagnetically disengaged friction clutch or brake between a shaft 1 and a gear-wheel 21 for use in machine tool change-speed gears comprises rollers 29 housed in apertures 28 in cages 27, with their axes inclined to a radius and engaging frictionally between interleaved clutch discs 16, 26, splined to the shaft and gear-wheel, so that a part sliding and part rolling motion of the rollers with respect thereto takes place, the discs being arranged outside the effective magnetic field. As shown, a stationary magnet body 2 and coil 3, connected to a housing (not shown) and journalled at 4 on the shaft 1, rotatably carry a disc comprising a non-magnetic ring 9 radially sandwiched between ferromagnetic rings 8, 10 forming part of the magnetic flux path. A flange 14 fast with a clutch body 12 keyed on the shaft 1 axially supports the clutch discs against the engaging thrust of helical springs 20 acting through a pressure plate 17, which also serves as the magnet armature for disengagement. In Fig. 3 (not shown) the magnet body and coil are keyed fast to the shaft and the helical engaging springs are replaced by a single Belleville type plate spring. In addition, passages are provided through the shaft and clutch body to feed air or liquid coolant and/or lubricant to the friction surfaces. If used as a dry clutch with air cooling, the rollers are steel and the discs are of sintered bronze or provided with asbestos facings. In each arrangement, disengagement is by energizing the coil with direct current for a short period up to saturation point so that the residual magnetism becomes greater than the spring force and maintains disengagement of the clutch, without current, engagement thereafter being effected by supplying alternating current or by a counter-impulse to nullify the residual effect. The residual magnetism may be increased by having both the armature and magnet body made of permanent magnet material or by disposing bar-shaped elements of such material in structural parts of the flux circuit. Additionally, the clutch may have a limit-switch adapted to control the energization of the magnet coil and operated by the armature during displacement thereof or a temperature dependent impulse member by means of which the energization of the coil can be controlled in dependence on an operating magnitude or factor for example, the temperature of the magnet coil during energization thereof such that the magnetic force produced by partial energization in conjunction with the residual force is greater than the spring force.