GB730677A - Improvements in and relating to electromagnetic adjustable drives - Google Patents

Abstract

730,677. Variable-speed gear; controlling clutches. AUTOMATA. Dec. 17, 1952 [Dec. 17, 1951], No. 31962/52. Class 80 (2). An electromagnetic adjustable drive comprises an electromagnetic friction clutch with one or two stationary windings, and an impulse transmitter which switches the magnet winding or windings alternatively on and off, and is characterized by the provision of means for varying at will the ratio between the duration of the current impulses and the duration of the intervals between them. The velocity ratio of the drive transmitted by the clutch is thus varied between the limits of direct drive, when the current flows continuously, and neutral, when no current impulses are supplied. The impulse transmitter may be a thermionic oscillator, the switching impulses of which can be adjusted by changes of electrical factors, or it may be a mechanical device. In one mechanical form a cylinder 9, Fig. 2, of insulating material has insets 10 of conducting material such as brass &c. engaged by a brush 11, slidable axially of the cylinder on rotation of a handwheel 5, the insets being electrically connected and the brush 11 &c. connected into the feed circuit of the electromagnetic clutch; the cylinder is rotated by a mechanical connection to the driving part of the clutch. In another form of impulse transmitter, Figs. 5, 6 (not shown), radial insets of conducting material on the surface of a disc of insulating material are engaged by a brush manually adjustable over a radius fixed relatively to the disc. As applied to reversing variable-ratio gearing, a motor 16 rotates bevel gears 18, 19 in opposite directions and either of two stationary windings 22, 23 are fed with impulses of current, according to the setting of a switch 31, to attract either of two discs 24, 25 into engagement with friction facings 20, 21 on the bevel gears, the impulses of current being fed in through the brush 11 and cylinder 9, slip ring 33 and brush 34; the cylinder 9 is rotated by a chain connection 30 with a shaft 29 itself rotated by a belt drive 26, 27, 28 from the driving shaft of the motor 16. As combined with a two-speed change-speed gear, the motor 16 drives a gear 36, Fig. 4, fast on a bush 38 freely rotatable on an axially slidable shaft 39 to which is secured a clutch disc 40 engageable with a friction lining 37 on the gear 36, the shaft also carrying an armature disc 42 for attraction by a stationary coil 41 when current is fed thereto, to move the shaft axially and engage the clutch; the impulse transmitter is rotated by a chain 45 passing over a sprocket 44 connected to the bush 38 and gear 36. The shaft 39 carries a pinion 50 giving a reduced drive through a train 51 ... 54 to a driven shaft 48, upward movement of a lever 49 from the position shown sliding gears 50, 51 and 53, 54 out of engagement and simultaneously engaging a positive clutch 55 for direct drive.